The following is a conversation with Matt Botmanek,
Director of Neuroscience Research at DeepMind.
He’s a brilliant, cross disciplinary mind,
navigating effortlessly between cognitive psychology,
computational neuroscience, and artificial intelligence.
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And now, here’s my conversation with Matt Botpenik.
How much of the human brain do you think we understand?
I think we’re at a weird moment
in the history of neuroscience in the sense that
I feel like we understand a lot about the brain
at a very high level, but a very coarse level.
When you say high level, what are you thinking?
Are you thinking functional?
Are you thinking structurally?
So in other words, what is the brain for?
What kinds of computation does the brain do?
What kinds of behaviors would we have to explain
if we were gonna look down at the mechanistic level?
And at that level, I feel like we understand
much, much more about the brain
than we did when I was in high school.
But it’s almost like we’re seeing it through a fog.
It’s only at a very coarse level.
We don’t really understand what the neuronal mechanisms are
that underlie these computations.
We’ve gotten better at saying,
what are the functions that the brain is computing
that we would have to understand
if we were gonna get down to the neuronal level?
And at the other end of the spectrum,
in the last few years, incredible progress has been made
in terms of technologies that allow us to see,
actually literally see, in some cases,
what’s going on at the single unit level,
even the dendritic level.
And then there’s this yawning gap in between.
Well, that’s interesting.
So at the high level,
so that’s almost a cognitive science level.
And then at the neuronal level,
that’s neurobiology and neuroscience,
just studying single neurons,
the synaptic connections and all the dopamine,
all the kind of neurotransmitters.
One blanket statement I should probably make
is that as I’ve gotten older,
I have become more and more reluctant
to make a distinction between psychology and neuroscience.
To me, the point of neuroscience
is to study what the brain is for.
If you’re a nephrologist
and you wanna learn about the kidney,
you start by saying, what is this thing for?
Well, it seems to be for taking blood on one side
that has metabolites in it that shouldn’t be there,
sucking them out of the blood
while leaving the good stuff behind,
and then excreting that in the form of urine.
That’s what the kidney is for.
It’s like obvious.
So the rest of the work is deciding how it does that.
And this, it seems to me,
is the right approach to take to the brain.
You say, well, what is the brain for?
The brain, as far as I can tell, is for producing behavior.
It’s for going from perceptual inputs to behavioral outputs,
and the behavioral outputs should be adaptive.
So that’s what psychology is about.
It’s about understanding the structure of that function.
And then the rest of neuroscience is about figuring out
how those operations are actually carried out
at a mechanistic level.
That’s really interesting, but so unlike the kidney,
the brain, the gap between the electrical signal
and behavior, so you truly see neuroscience
as the science that touches behavior,
how the brain generates behavior,
or how the brain converts raw visual information
Like, you basically see cognitive science,
psychology, and neuroscience as all one science.
Yeah, it’s a personal statement.
Is that a hopeful or a realistic statement?
So certainly you will be correct in your feeling
in some number of years, but that number of years
could be 200, 300 years from now.
Oh, well, there’s a…
Is that aspirational or is that pragmatic engineering
feeling that you have?
It’s both in the sense that this is what I hope
and expect will bear fruit over the coming decades,
but it’s also pragmatic in the sense that I’m not sure
what we’re doing in either psychology or neuroscience
if that’s not the framing.
I don’t know what it means to understand the brain
if there’s no, if part of the enterprise
is not about understanding the behavior
that’s being produced.
I mean, yeah, but I would compare it
to maybe astronomers looking at the movement
of the planets and the stars without any interest
of the underlying physics, right?
And I would argue that at least in the early days,
there is some value to just tracing the movement
of the planets and the stars without thinking
about the physics too much because it’s such a big leap
to start thinking about the physics
before you even understand even the basic structural
Oh, I agree with that.
But you’re saying in the end, the goal should be
to deeply understand.
Well, right, and I think…
So I thought about this a lot when I was in grad school
because a lot of what I studied in grad school
was psychology and I found myself a little bit confused
about what it meant to…
It seems like what we were talking about a lot of the time
were virtual causal mechanisms.
Like, oh, well, you know, attentional selection
then selects some object in the environment
and that is then passed on to the motor, you know,
information about that is passed on to the motor system.
But these are virtual mechanisms.
These are, you know, they’re metaphors.
They’re, you know, there’s no reduction going on
in that conversation to some physical mechanism that,
you know, which is really what it would take
to fully understand, you know, how behavior is rising.
But the causal mechanisms are definitely neurons interacting.
I’m willing to say that at this point in history.
So in psychology, at least for me personally,
there was this strange insecurity about trafficking
in these metaphors, you know,
which were supposed to explain the function of the mind.
If you can’t ground them in physical mechanisms,
then what is the explanatory validity of these explanations?
And I managed to soothe my own nerves
by thinking about the history of genetics research.
So I’m very far from being an expert
on the history of this field.
But I know enough to say that, you know,
Mendelian genetics preceded, you know, Watson and Crick.
And so there was a significant period of time
during which people were, you know,
productively investigating the structure of inheritance
using what was essentially a metaphor,
the notion of a gene, you know.
Oh, genes do this and genes do that.
But, you know, where are the genes?
They’re sort of an explanatory thing that we made up.
And we ascribed to them these causal properties.
Oh, there’s a dominant, there’s a recessive,
and then they recombine it.
And then later, there was a kind of blank there
that was filled in with a physical mechanism.
That connection was made.
But it was worth having that metaphor
because that gave us a good sense
of what kind of causal mechanism we were looking for.
And the fundamental metaphor of cognition, you said,
is the interaction of neurons.
Is that, what is the metaphor?
No, no, the metaphor,
the metaphors we use in cognitive psychology
are things like attention, the way that memory works.
I retrieve something from memory, right?
A memory retrieval occurs.
What is that?
You know, that’s not a physical mechanism
that I can examine in its own right.
But it’s still worth having, that metaphorical level.
Yeah, so yeah, I misunderstood actually.
So the higher level of abstractions
is the metaphor that’s most useful.
But what about, so how does that connect
to the idea that that arises from interaction of neurons?
Well, even, is the interaction of neurons
also not a metaphor to you?
Or is it literally, like that’s no longer a metaphor.
That’s already the lowest level of abstractions
that could actually be directly studied.
Well, I’m hesitating because I think
what I want to say could end up being controversial.
So what I want to say is, yes,
the interactions of neurons, that’s not metaphorical.
That’s a physical fact.
That’s where the causal interactions actually occur.
Now, I suppose you could say,
well, even that is metaphorical relative
to the quantum events that underlie.
I don’t want to go down that rabbit hole.
It’s always turtles on top of turtles.
Yeah, there’s turtles all the way down.
There’s a reduction that you can do.
You can say these psychological phenomena
can be explained through a very different
kind of causal mechanism,
which has to do with neurotransmitter release.
And so what we’re really trying to do
in neuroscience writ large, as I say,
which for me includes psychology,
is to take these psychological phenomena
and map them onto neural events.
I think remaining forever at the level of description
that is natural for psychology,
for me personally, would be disappointing.
I want to understand how mental activity
arises from neural activity.
But the converse is also true.
Studying neural activity without any sense
of what you’re trying to explain,
to me feels like at best groping around at random.
Now, you’ve kind of talked about this bridging
of the gap between psychology and neuroscience,
but do you think it’s possible,
like my love is, like I fell in love with psychology
and psychiatry in general with Freud
and when I was really young,
and I hoped to understand the mind.
And for me, understanding the mind,
at least at that young age before I discovered AI
and even neuroscience was to, is psychology.
And do you think it’s possible to understand the mind
without getting into all the messy details of neuroscience?
Like you kind of mentioned to you it’s appealing
to try to understand the mechanisms at the lowest level,
but do you think that’s needed,
that’s required to understand how the mind works?
That’s an important part of the whole picture,
but I would be the last person on earth
to suggest that that reality
renders psychology in its own right unproductive.
I trained as a psychologist.
I am fond of saying that I have learned much more
from psychology than I have from neuroscience.
To me, psychology is a hugely important discipline.
And one thing that warms in my heart is that
ways of investigating behavior
that have been native to cognitive psychology
since it’s dawn in the 60s
are starting to become,
they’re starting to become interesting to AI researchers
for a variety of reasons.
And that’s been exciting for me to see.
Can you maybe talk a little bit about what you see
as beautiful aspects of psychology,
maybe limiting aspects of psychology?
I mean, maybe just start it off as a science, as a field.
To me, it was when I understood what psychology is,
like the way it’s actually carried out,
it was really disappointing to see two aspects.
One is how small the N is,
how small the number of subject is in the studies.
And two, it was disappointing to see
how controlled the entire,
how much it was in the lab.
It wasn’t studying humans in the wild.
There was no mechanism for studying humans in the wild.
So that’s where I became a little bit disillusioned
And then the modern world of the internet
is so exciting to me.
The Twitter data or YouTube data,
data of human behavior on the internet becomes exciting
because the N grows and then in the wild grows.
But that’s just my narrow sense.
Like, do you have a optimistic or pessimistic
cynical view of psychology?
How do you see the field broadly?
When I was in graduate school,
it was early enough that there was still a thrill
in seeing that there were ways of doing,
there were ways of doing experimental science
that provided insight to the structure of the mind.
One thing that impressed me most when I was at that stage
in my education was neuropsychology,
looking at, analyzing the behavior of populations
who had brain damage of different kinds
and trying to understand what the specific deficits were
that arose from a lesion in a particular part of the brain.
And the kind of experimentation that was done
and that’s still being done to get answers in that context
was so creative and it was so deliberate.
It was good science.
An experiment answered one question but raised another
and somebody would do an experiment
that answered that question.
And you really felt like you were narrowing in on
some kind of approximate understanding
of what this part of the brain was for.
Do you have an example from memory
of what kind of aspects of the mind
could be studied in this kind of way?
I mean, the very detailed neuropsychological studies
of language function,
looking at production and reception
and the relationship between visual function,
reading and auditory and semantic.
There were these, and still are, these beautiful models
that came out of that kind of research
that really made you feel like you understood something
that you hadn’t understood before
about how language processing is organized in the brain.
But having said all that,
I think you are, I mean, I agree with you
that the cost of doing highly controlled experiments
is that you, by construction, miss out on the richness
and complexity of the real world.
One thing that, so I was drawn into science
by what in those days was called connectionism,
which is, of course, what we now call deep learning.
And at that point in history,
neural networks were primarily being used
in order to model human cognition.
They weren’t yet really useful for industrial applications.
So you always found neural networks
in biological form beautiful.
Oh, neural networks were very concretely the thing
that drew me into science.
I was handed, are you familiar with the PDP books
from the 80s when I was in,
I went to medical school before I went into science.
I also did a graduate degree in art history,
so I’m kind of exploring.
Well, art history, I understand.
That’s just a curious, creative mind.
But medical school, with the dream of what,
if we take that slight tangent?
What, did you want to be a surgeon?
I actually was quite interested in surgery.
I was interested in surgery and psychiatry.
And I thought, I must be the only person on the planet
who was torn between those two fields.
And I said exactly that to my advisor in medical school,
who turned out, I found out later,
to be a famous psychoanalyst.
And he said to me, no, no, it’s actually not so uncommon
to be interested in surgery and psychiatry.
And he conjectured that the reason
that people develop these two interests
is that both fields are about going beneath the surface
and kind of getting into the kind of secret.
I mean, maybe you understand this as someone
who was interested in psychoanalysis.
There’s sort of a, there’s a cliche phrase
that people use now, like in NPR,
the secret life of blankety blank, right?
And that was part of the thrill of surgery,
was seeing the secret activity
that’s inside everybody’s abdomen and thorax.
That’s a very poetic way to connect it to disciplines
that are very, practically speaking,
different from each other.
That’s for sure, that’s for sure, yes.
So how did we get onto medical school?
So I was in medical school
and I was doing a psychiatry rotation
and my kind of advisor in that rotation
asked me what I was interested in.
And I said, well, maybe psychiatry.
He said, why?
And I said, well, I’ve always been interested
in how the brain works.
I’m pretty sure that nobody’s doing scientific research
that addresses my interests,
which are, I didn’t have a word for it then,
but I would have said about cognition.
And he said, well, you know, I’m not sure that’s true.
You might be interested in these books.
And he pulled down the PDB books from his shelf
and they were still shrink wrapped.
He hadn’t read them, but he handed them to me.
He said, you feel free to borrow these.
And that was, you know, I went back to my dorm room
and I just, you know, read them cover to cover.
And what’s PDB?
Parallel distributed processing,
which was one of the original names for deep learning.
And so I apologize for the romanticized question,
but what idea in the space of neuroscience
and the space of the human brain is to you
the most beautiful, mysterious, surprising?
What had always fascinated me,
even when I was a pretty young kid, I think,
was the paradox that lies in the fact
that the brain is so mysterious
and seems so distant.
But at the same time,
it’s responsible for the full transparency
of everyday life.
The brain is literally what makes everything obvious
And there’s always one in the room with you.
I used to teach, when I taught at Princeton,
I used to teach a cognitive neuroscience course.
And the very last thing I would say to the students was,
you know, people often,
when people think of scientific inspiration,
the metaphor is often, well, look to the stars.
The stars will inspire you to wonder at the universe
and think about your place in it and how things work.
And I’m all for looking at the stars,
but I’ve always been much more inspired.
And my sense of wonder comes from the,
not from the distant, mysterious stars,
but from the extremely intimately close brain.
There’s something just endlessly fascinating
to me about that.
The, like, just like you said,
the one that’s close and yet distant
in terms of our understanding of it.
Do you, are you also captivated by the fact
that this very conversation is happening
because two brains are communicating so that?
The, I guess what I mean is the subjective nature
of the experience, if it can take a small attention
into the mystical of it, the consciousness,
or when you were saying you’re captivated
by the idea of the brain,
are you talking about specifically
the mechanism of cognition?
Or are you also just, like, at least for me,
it’s almost like paralyzing the beauty and the mystery
of the fact that it creates the entirety of the experience,
not just the reasoning capability, but the experience.
Well, I definitely resonate with that latter thought.
And I often find discussions of artificial intelligence
to be disappointingly narrow.
Speaking as someone who has always had an interest in art.
I was just gonna go there
because it sounds like somebody who has an interest in art.
Yeah, I mean, there are many layers
to full bore human experience.
And in some ways it’s not enough to say,
oh, well, don’t worry, we’re talking about cognition,
but we’ll add emotion, you know?
There’s an incredible scope
to what humans go through in every moment.
And yes, so that’s part of what fascinates me,
is that our brains are producing that.
But at the same time, it’s so mysterious to us.
Our brains are literally in our heads
producing this experience.
Producing the experience.
And yet it’s so mysterious to us.
And so, and the scientific challenge
of getting at the actual explanation for that
is so overwhelming.
That’s just, I don’t know.
Certain people have fixations on particular questions
and that’s always, that’s just always been mine.
Yeah, I would say the poetry of that is fascinating.
And I’m really interested in natural language as well.
And when you look at artificial intelligence community,
it always saddens me how much
when you try to create a benchmark
for the community to gather around,
how much of the magic of language is lost
when you create that benchmark.
That there’s something, we talk about experience,
the music of the language, the wit,
the something that makes a rich experience,
something that would be required to pass
the spirit of the Turing test is lost in these benchmarks.
And I wonder how to get it back in
because it’s very difficult.
The moment you try to do like real good rigorous science,
you lose some of that magic.
When you try to study cognition
in a rigorous scientific way,
it feels like you’re losing some of the magic.
The seeing cognition in a mechanistic way
that AI folk at this stage in our history.
Well, I agree with you, but at the same time,
one thing that I found really exciting
about that first wave of deep learning models in cognition
was the fact that the people who were building these models
were focused on the richness and complexity
of human cognition.
So an early debate in cognitive science,
which I sort of witnessed as a grad student
was about something that sounds very dry,
which is the formation of the past tense.
But there were these two camps.
One said, well, the mind encodes certain rules
and it also has a list of exceptions
because of course, the rule is add ED,
but that’s not always what you do.
So you have to have a list of exceptions.
And then there were the connectionists
who evolved into the deep learning people who said,
well, if you look carefully at the data,
if you actually look at corpora, like language corpora,
it turns out to be very rich
because yes, there are most verbs
that you just tack on ED, and then there are exceptions,
but there are rules that the exceptions aren’t just random.
There are certain clues to which verbs
should be exceptional.
And then there are exceptions to the exceptions.
And there was a word that was kind of deployed
in order to capture this, which was quasi regular.
In other words, there are rules, but it’s messy.
And there’s either structure even among the exceptions.
And it would be, yeah, you could try to write down,
we could try to write down the structure
in some sort of closed form,
but really the right way to understand
how the brain is handling all this,
and by the way, producing all of this,
is to build a deep neural network
and train it on this data
and see how it ends up representing all of this richness.
So the way that deep learning
was deployed in cognitive psychology
was that was the spirit of it.
It was about that richness.
And that’s something that I always found very compelling,
Is there something especially interesting
and profound to you
in terms of our current deep learning neural network,
artificial neural network approaches,
and whatever we do understand
about the biological neural networks in our brain?
Is there, there’s quite a few differences.
Are some of them to you,
either interesting or perhaps profound
in terms of the gap we might want to try to close
in trying to create a human level intelligence?
What I would say here is something
that a lot of people are saying,
which is that one seeming limitation
of the systems that we’re building now
is that they lack the kind of flexibility,
the readiness to sort of turn on a dime
when the context calls for it
that is so characteristic of human behavior.
So is that connected to you to the,
like which aspect of the neural networks in our brain
is that connected to?
Is that closer to the cognitive science level of,
now again, see like my natural inclination
is to separate into three disciplines of neuroscience,
cognitive science and psychology.
And you’ve already kind of shut that down
by saying you’re kind of see them as separate,
but just to look at those layers,
I guess where is there something about the lowest layer
of the way the neural neurons interact
that is profound to you in terms of this difference
to the artificial neural networks,
or is all the key differences
at a higher level of abstraction?
One thing I often think about is that,
if you take an introductory computer science course
and they are introducing you to the notion
of Turing machines,
one way of articulating
what the significance of a Turing machine is,
is that it’s a machine emulator.
It can emulate any other machine.
And that to me,
that way of looking at a Turing machine
really sticks with me.
I think of humans as maybe sharing
in some of that character.
We’re capacity limited,
we’re not Turing machines obviously,
but we have the ability to adapt behaviors
that are very much unlike anything we’ve done before,
but there’s some basic mechanism
that’s implemented in our brain
that allows us to run software.
But just on that point, you mentioned Turing machine,
but nevertheless, it’s fundamentally
our brains are just computational devices in your view.
Is that what you’re getting at?
It was a little bit unclear to this line you drew.
Is there any magic in there
or is it just basic computation?
I’m happy to think of it as just basic computation,
but mind you, I won’t be satisfied
until somebody explains to me
what the basic computations are
that are leading to the full richness of human cognition.
It’s not gonna be enough for me
to understand what the computations are
that allow people to do arithmetic or play chess.
I want the whole thing.
And a small tangent,
because you kind of mentioned coronavirus,
there’s group behavior.
Is there something interesting
to your search of understanding the human mind
where behavior of large groups
or just behavior of groups is interesting,
seeing that as a collective mind,
as a collective intelligence,
perhaps seeing the groups of people
as a single intelligent organisms,
especially looking at the reinforcement learning work
you’ve done recently.
Well, yeah, I can’t.
I mean, I have the honor of working
with a lot of incredibly smart people
and I wouldn’t wanna take any credit
for leading the way on the multiagent work
that’s come out of my group or DeepMind lately,
but I do find it fascinating.
And I mean, I think it can’t be debated.
You know, human behavior arises within communities.
That just seems to me self evident.
But to me, it is self evident,
but that seems to be a profound aspects
of something that created.
That was like, if you look at like 2001 Space Odyssey
when the monkeys touched the…
That’s the magical moment I think Yuval Harari argues
that the ability of our large numbers of humans
to hold an idea, to converge towards idea together,
like you said, shaking hands versus bumping elbows,
somehow converge without being in a room altogether,
just kind of this like distributed convergence
towards an idea over a particular period of time
seems to be fundamental to just every aspect
of our cognition, of our intelligence,
because humans, I will talk about reward,
but it seems like we don’t really have
a clear objective function under which we operate,
but we all kind of converge towards one somehow.
And that to me has always been a mystery
that I think is somehow productive
for also understanding AI systems.
But I guess that’s the next step.
The first step is try to understand the mind.
Well, I don’t know.
I mean, I think there’s something to the argument
that that kind of like strictly bottom up approach
In other words, there are basic phenomena,
basic aspects of human intelligence
that can only be understood in the context of groups.
I’m perfectly open to that.
I’ve never been particularly convinced by the notion
that we should consider intelligence
to inhere at the level of communities.
I don’t know why, I’m sort of stuck on the notion
that the basic unit that we want to understand
is individual humans.
And if we have to understand that
in the context of other humans, fine.
But for me, intelligence is just,
I stubbornly define it as something
that is an aspect of an individual human.
That’s just my, I don’t know if that’s a matter of taste.
I’m with you, but that could be the reductionist dream
of a scientist because you can understand a single human.
It also is very possible that intelligence can only arise
when there’s multiple intelligences.
When there’s multiple sort of, it’s a sad thing,
if that’s true, because it’s very difficult to study.
But if it’s just one human,
that one human would not be homosapien,
would not become that intelligent.
That’s a possibility.
I’m with you.
One thing I will say along these lines
is that I think a serious effort
to understand human intelligence
and maybe to build humanlike intelligence
needs to pay just as much attention
to the structure of the environment
as to the structure of the cognizing system,
whether it’s a brain or an AI system.
That’s one thing I took away actually
from my early studies with the pioneers
of neural network research,
people like Jay McClelland and John Cohen.
The structure of cognition is really,
it’s only partly a function of the architecture of the brain
and the learning algorithms that it implements.
What really shapes it is the interaction of those things
with the structure of the world
in which those things are embedded.
And that’s especially important for,
that’s made most clear in reinforcement learning
where the simulated environment is,
you can only learn as much as you can simulate.
And that’s what DeepMind made very clear
with the other aspect of the environment,
which is the self play mechanism of the other agent,
of the competitive behavior,
which the other agent becomes the environment essentially.
And that’s, I mean, one of the most exciting ideas in AI
is the self play mechanism that’s able to learn successfully.
So there you go.
There’s a thing where competition is essential
for learning, at least in that context.
So if we can step back into another sort of beautiful world,
which is the actual mechanics,
the dirty mess of it of the human brain,
is there something for people who might not know?
Is there something you can comment on
or describe the key parts of the brain
that are important for intelligence or just in general,
what are the different parts of the brain
that you’re curious about that you’ve studied
and that are just good to know about
when you’re thinking about cognition?
Well, my area of expertise, if I have one,
is prefrontal cortex.
So, you know. What’s that?
Where do we?
It depends on who you ask.
The technical definition is anatomical.
There are parts of your brain
that are responsible for motor behavior
and they’re very easy to identify.
And the region of your cerebral cortex,
the sort of outer crust of your brain
that lies in front of those
is defined as the prefrontal cortex.
And when you say anatomical, sorry to interrupt,
so that’s referring to sort of the geographic region
as opposed to some kind of functional definition.
Exactly, so this is kind of the coward’s way out.
I’m telling you what the prefrontal cortex is
just in terms of what part of the real estate it occupies.
It’s the thing in the front of the brain.
And in fact, the early history
of neuroscientific investigation
of what this front part of the brain does
is sort of funny to read
because it was really World War I
that started people down this road
of trying to figure out what different parts of the brain,
the human brain do in the sense
that there were a lot of people with brain damage
who came back from the war with brain damage.
And that provided, as tragic as that was,
it provided an opportunity for scientists
to try to identify the functions of different brain regions.
And that was actually incredibly productive,
but one of the frustrations that neuropsychologists faced
was they couldn’t really identify exactly
what the deficit was that arose from damage
to these most kind of frontal parts of the brain.
It was just a very difficult thing to pin down.
There were a couple of neuropsychologists
who identified through a large amount
of clinical experience and close observation,
they started to put their finger on a syndrome
that was associated with frontal damage.
Actually, one of them was a Russian neuropsychologist
named Luria, who students of cognitive psychology still read.
And what he started to figure out was that
the frontal cortex was somehow involved in flexibility,
in guiding behaviors that required someone
to override a habit, or to do something unusual,
or to change what they were doing in a very flexible way
from one moment to another.
So focused on like new experiences.
And so the way your brain processes
and acts in new experiences.
Yeah, what later helped bring this function
into better focus was a distinction
between controlled and automatic behavior,
or in other literatures, this is referred to
as habitual behavior versus goal directed behavior.
So it’s very, very clear that the human brain
has pathways that are dedicated to habits,
to things that you do all the time,
and they need to be automatized
so that they don’t require you to concentrate too much.
So that leaves your cognitive capacity
free to do other things.
Just think about the difference
between driving when you’re learning to drive
versus driving after you’re a fairly expert.
There are brain pathways that slowly absorb
those frequently performed behaviors
so that they can be habits, so that they can be automatic.
That’s kind of like the purest form of learning.
I guess it’s happening there, which is why,
I mean, this is kind of jumping ahead,
which is why that perhaps is the most useful for us
to focusing on and trying to see
how artificial intelligence systems can learn.
Is that the way you think?
I do think about this distinction
between controlled and automatic,
or goal directed and habitual behavior a lot
in thinking about where we are in AI research.
But just to finish the kind of dissertation here,
the role of the prefrontal cortex
is generally understood these days
sort of in contradistinction to that habitual domain.
In other words, the prefrontal cortex
is what helps you override those habits.
It’s what allows you to say,
well, what I usually do in this situation is X,
but given the context, I probably should do Y.
I mean, the elbow bump is a great example, right?
Reaching out and shaking hands
is probably a habitual behavior,
and it’s the prefrontal cortex that allows us
to bear in mind that there’s something unusual
going on right now, and in this situation,
I need to not do the usual thing.
The kind of behaviors that Luria reported,
and he built tests for detecting these kinds of things,
were exactly like this.
So in other words, when I stick out my hand,
I want you instead to present your elbow.
A patient with frontal damage
would have a great deal of trouble with that.
Somebody proffering their hand would elicit a handshake.
The prefrontal cortex is what allows us to say,
hold on, hold on, that’s the usual thing,
but I have the ability to bear in mind
even very unusual contexts and to reason about
what behavior is appropriate there.
Just to get a sense, are us humans special
in the presence of the prefrontal cortex?
Do mice have a prefrontal cortex?
Do other mammals that we can study?
If no, then how do they integrate new experiences?
Yeah, that’s a really tricky question
and a very timely question
because we have revolutionary new technologies
for monitoring, measuring,
and also causally influencing neural behavior
in mice and fruit flies.
And these techniques are not fully available
even for studying brain function in monkeys,
let alone humans.
And so it’s a very sort of, for me at least,
a very urgent question whether the kinds of things
that we wanna understand about human intelligence
can be pursued in these other organisms.
And to put it briefly, there’s disagreement.
People who study fruit flies will often tell you,
hey, fruit flies are smarter than you think.
And they’ll point to experiments where fruit flies
were able to learn new behaviors,
were able to generalize from one stimulus to another
in a way that suggests that they have abstractions
that guide their generalization.
I’ve had many conversations in which
I will start by observing,
recounting some observation about mouse behavior
where it seemed like mice were taking an awfully long time
to learn a task that for a human would be profoundly trivial.
And I will conclude from that,
that mice really don’t have the cognitive flexibility
that we want to explain.
And then a mouse researcher will say to me,
well, hold on, that experiment may not have worked
because you asked a mouse to deal with stimuli
and behaviors that were very unnatural for the mouse.
If instead you kept the logic of the experiment the same,
but presented the information in a way
that aligns with what mice are used to dealing with
in their natural habitats,
you might find that a mouse actually has more intelligence
than you think.
And then they’ll go on to show you videos
of mice doing things in their natural habitat,
which seem strikingly intelligent,
dealing with physical problems.
I have to drag this piece of food back to my lair,
but there’s something in my way
and how do I get rid of that thing?
So I think these are open questions
to put it, to sum that up.
And then taking a small step back related to that
is you kind of mentioned we’re taking a little shortcut
by saying it’s a geographic part of the prefrontal cortex
is a region of the brain.
But if we, what’s your sense in a bigger philosophical view,
prefrontal cortex and the brain in general,
do you have a sense that it’s a set of subsystems
in the way we’ve kind of implied
that are pretty distinct or to what degree is it that
or to what degree is it a giant interconnected mess
where everything kind of does everything
and it’s impossible to disentangle them?
I think there’s overwhelming evidence
that there’s functional differentiation,
that it’s clearly not the case
that all parts of the brain are doing the same thing.
This follows immediately from the kinds of studies
of brain damage that we were chatting about before.
It’s obvious from what you see
if you stick an electrode in the brain
and measure what’s going on at the level of neural activity.
Having said that, there are two other things to add,
which kind of, I don’t know,
maybe tug in the other direction.
One is that it’s when you look carefully
at functional differentiation in the brain,
what you usually end up concluding,
at least this is my observation of the literature,
is that the differences between regions are graded
rather than being discreet.
So it doesn’t seem like it’s easy
to divide the brain up into true modules
that have clear boundaries and that have
you know, clear channels of communication between them.
And this applies to the prefrontal cortex?
Yeah, oh yeah.
The prefrontal cortex is made up
of a bunch of different subregions,
the functions of which are not clearly defined
and the borders of which seem to be quite vague.
And then there’s another thing that’s popping up
in very recent research, which, you know, which,
involves application of these new techniques,
which there are a number of studies that suggest that
parts of the brain that we would have previously thought
were quite focused in their function
are actually carrying signals
that we wouldn’t have thought would be there.
For example, looking in the primary visual cortex,
which is classically thought of as basically
the first cortical way station
for processing visual information.
Basically what it should care about is, you know,
where are the edges in this scene that I’m viewing?
It turns out that if you have enough data,
you can recover information from primary visual cortex
about all sorts of things.
Like, you know, what behavior the animal is engaged
in right now and how much reward is on offer
in the task that it’s pursuing.
So it’s clear that even regions whose function
is pretty well defined at a core screen
are nonetheless carrying some information
about information from very different domains.
So, you know, the history of neuroscience
is sort of this oscillation between the two views
that you articulated, you know, the kind of modular view
and then the big, you know, mush view.
And, you know, I think, I guess we’re gonna end up
somewhere in the middle.
Which is unfortunate for our understanding
because there’s something about our, you know,
conceptual system that finds it’s easy to think about
a modularized system and easy to think about
a completely undifferentiated system.
But something that kind of lies in between is confusing.
But we’re gonna have to get used to it, I think.
Unless we can understand deeply the lower level mechanism
of neuronal communication.
But on that topic, you kind of mentioned information.
Just to get a sense, I imagine something
that there’s still mystery and disagreement on
is how does the brain carry information and signal?
Like what in your sense is the basic mechanism
of communication in the brain?
Well, I guess I’m old fashioned in that I consider
the networks that we use in deep learning research
to be a reasonable approximation to, you know,
the mechanisms that carry information in the brain.
So the usual way of articulating that is to say,
what really matters is a rate code.
What matters is how quickly is an individual neuron spiking?
You know, what’s the frequency at which it’s spiking?
Is it right?
So the timing of the spike.
Yeah, is it firing fast or slow?
Let’s, you know, let’s put a number on that.
And that number is enough to capture
what neurons are doing.
There’s, you know, there’s still uncertainty
about whether that’s an adequate description
of how information is transmitted within the brain.
There, you know, there are studies that suggest
that the precise timing of spikes matters.
There are studies that suggest that there are computations
that go on within the dendritic tree, within a neuron,
that are quite rich and structured
and that really don’t equate to anything that we’re doing
in our artificial neural networks.
Having said that, I feel like we can get,
I feel like we’re getting somewhere
by sticking to this high level of abstraction.
Just the rate, and by the way,
we’re talking about the electrical signal.
I remember reading some vague paper somewhere recently
where the mechanical signal, like the vibrations
or something of the neurons, also communicates information.
I haven’t seen that, but.
There’s somebody who was arguing
that the electrical signal, this is in a nature paper,
something like that, where the electrical signal
is actually a side effect of the mechanical signal.
But I don’t think that changes the story.
But it’s almost an interesting idea
that there could be a deeper, it’s always like in physics
with quantum mechanics, there’s always a deeper story
that could be underlying the whole thing.
But you think it’s basically the rate of spiking
that gets us, that’s like the lowest hanging fruit
that can get us really far.
This is a classical view.
I mean, this is not, the only way in which this stance
would be controversial is in the sense
that there are members of the neuroscience community
who are interested in alternatives.
But this is really a very mainstream view.
The way that neurons communicate
is that neurotransmitters arrive,
they wash up on a neuron, the neuron has receptors
for those transmitters, the meeting of the transmitter
with these receptors changes the voltage of the neuron.
And if enough voltage change occurs, then a spike occurs,
one of these like discrete events.
And it’s that spike that is conducted down the axon
and leads to neurotransmitter release.
This is just like neuroscience 101.
This is like the way the brain is supposed to work.
Now, what we do when we build artificial neural networks
of the kind that are now popular in the AI community
is that we don’t worry about those individual spikes.
We just worry about the frequency
at which those spikes are being generated.
And people talk about that as the activity of a neuron.
And so the activity of units in a deep learning system
is broadly analogous to the spike rate of a neuron.
There are people who believe that there are other forms
of communication in the brain.
In fact, I’ve been involved in some research recently
that suggests that the voltage fluctuations
that occur in populations of neurons
that are sort of below the level of spike production
may be important for communication.
But I’m still pretty old school in the sense
that I think that the things that we’re building
in AI research constitute reasonable models
of how a brain would work.
Let me ask just for fun a crazy question, because I can.
Do you think it’s possible we’re completely wrong
about the way this basic mechanism
of neuronal communication, that the information
is stored in some very different kind of way in the brain?
Oh, heck yes.
I mean, look, I wouldn’t be a scientist
if I didn’t think there was any chance we were wrong.
But I mean, if you look at the history
of deep learning research as it’s been applied
to neuroscience, of course the vast majority
of deep learning research these days isn’t about neuroscience.
But if you go back to the 1980s,
there’s sort of an unbroken chain of research
in which a particular strategy is taken,
which is, hey, let’s train a deep learning system.
Let’s train a multi layer neural network
on this task that we trained our rat on,
or our monkey on, or this human being on.
And then let’s look at what the units
deep in the system are doing.
And let’s ask whether what they’re doing
resembles what we know about what neurons
deep in the brain are doing.
And over and over and over and over,
that strategy works in the sense that
the learning algorithms that we have access to,
which typically center on back propagation,
they give rise to patterns of activity,
patterns of response,
patterns of neuronal behavior in these artificial models
that look hauntingly similar to what you see in the brain.
And is that a coincidence?
At a certain point, it starts looking like such coincidence
is unlikely to not be deeply meaningful, yeah.
Yeah, the circumstantial evidence is overwhelming.
But it could be.
But you’re always open to total flipping at the table.
Hey, of course.
So you have coauthored several recent papers
that sort of weave beautifully between the world
of neuroscience and artificial intelligence.
And maybe if we could, can we just try to dance around
and talk about some of them?
Maybe try to pick out interesting ideas
that jump to your mind from memory.
So maybe looking at, we were talking about
the prefrontal cortex, the 2018, I believe, paper
called the Prefrontal Cortex
as a Meta Reinforcement Learning System.
What, is there a key idea
that you can speak to from that paper?
Yeah, I mean, the key idea is about meta learning.
What is meta learning?
Meta learning is, by definition,
a situation in which you have a learning algorithm
and the learning algorithm operates in such a way
that it gives rise to another learning algorithm.
In the earliest applications of this idea,
you had one learning algorithm sort of adjusting
the parameters on another learning algorithm.
But the case that we’re interested in this paper
is one where you start with just one learning algorithm
and then another learning algorithm kind of emerges
out of thin air.
I can say more about what I mean by that.
I don’t mean to be scurrentist,
but that’s the idea of meta learning.
It relates to the old idea in psychology
of learning to learn.
Situations where you have experiences
that make you better at learning something new.
A familiar example would be learning a foreign language.
The first time you learn a foreign language,
it may be quite laborious and disorienting
and novel, but let’s say you’ve learned
two foreign languages.
The third foreign language, obviously,
is gonna be much easier to pick up.
Because you’ve learned how to learn.
You know how this goes.
You know, okay, I’m gonna have to learn how to conjugate.
I’m gonna have to…
That’s a simple form of meta learning
in the sense that there’s some slow learning mechanism
that’s helping you kind of update
your fast learning mechanism.
Does that make sense?
So how from our understanding from the psychology world,
from neuroscience, our understanding
how meta learning might work in the human brain,
what lessons can we draw from that
that we can bring into the artificial intelligence world?
Well, yeah, so the origin of that paper
was in AI work that we were doing in my group.
We were looking at what happens
when you train a recurrent neural network
using standard reinforcement learning algorithms.
But you train that network, not just in one task,
but you train it in a bunch of interrelated tasks.
And then you ask what happens when you give it
yet another task in that sort of line of interrelated tasks.
And what we started to realize is that
a form of meta learning spontaneously happens
in recurrent neural networks.
And the simplest way to explain it is to say
a recurrent neural network has a kind of memory
in its activation patterns.
It’s recurrent by definition in the sense
that you have units that connect to other units,
that connect to other units.
So you have sort of loops of connectivity,
which allows activity to stick around
and be updated over time.
In psychology we call, in neuroscience
we call this working memory.
It’s like actively holding something in mind.
And so that memory gives
the recurrent neural network a dynamics, right?
The way that the activity pattern evolves over time
is inherent to the connectivity
of the recurrent neural network, okay?
So that’s idea number one.
Now, the dynamics of that network are shaped
by the connectivity, by the synaptic weights.
And those synaptic weights are being shaped
by this reinforcement learning algorithm
that you’re training the network with.
So the punchline is if you train a recurrent neural network
with a reinforcement learning algorithm
that’s adjusting its weights,
and you do that for long enough,
the activation dynamics will become very interesting, right?
So imagine I give you a task
where you have to press one button or another,
left button or right button.
And there’s some probability
that I’m gonna give you an M&M
if you press the left button,
and there’s some probability I’ll give you an M&M
if you press the other button.
And you have to figure out what those probabilities are
just by trying things out.
But as I said before,
instead of just giving you one of these tasks,
I give you a whole sequence.
You know, I give you two buttons
and you figure out which one’s best.
And I go, good job, here’s a new box.
Two new buttons, you have to figure out which one’s best.
Good job, here’s a new box.
And every box has its own probabilities
and you have to figure it out.
So if you train a recurrent neural network
on that kind of sequence of tasks,
what happens, it seemed almost magical to us
when we first started kind of realizing what was going on.
The slow learning algorithm that’s adjusting
the synaptic weights,
those slow synaptic changes give rise to a network dynamics
that themselves, that, you know,
the dynamics themselves turn into a learning algorithm.
So in other words, you can tell this is happening
by just freezing the synaptic weights saying,
okay, no more learning, you’re done.
Here’s a new box, figure out which button is best.
And the recurrent neural network will do this just fine.
There’s no, like it figures out which button is best.
It kind of transitions from exploring the two buttons
to just pressing the one that it likes best
in a very rational way.
How is that happening?
It’s happening because the activity dynamics
of the network have been shaped by the slow learning process
that’s occurred over many, many boxes.
And so what’s happened is that this slow learning algorithm
that’s slowly adjusting the weights
is changing the dynamics of the network,
the activity dynamics into its own learning algorithm.
And as we were kind of realizing that this is a thing,
it just so happened that the group that was working on this
included a bunch of neuroscientists
and it started kind of ringing a bell for us,
which is to say that we thought this sounds a lot
like the distinction between synaptic learning
and activity, synaptic memory
and activity based memory in the brain.
And it also reminded us of recurrent connectivity
that’s very characteristic of prefrontal function.
So this is kind of why it’s good to have people working
on AI that know a little bit about neuroscience
and vice versa, because we started thinking
about whether we could apply this principle to neuroscience.
And that’s where the paper came from.
So the kind of principle of the recurrence
they can see in the prefrontal cortex,
then you start to realize that it’s possible
for something like an idea of a learning
to learn emerging from this learning process
as long as you keep varying the environment sufficiently.
Exactly, so the kind of metaphorical transition
we made to neuroscience was to think,
okay, well, we know that the prefrontal cortex
is highly recurrent.
We know that it’s an important locus for working memory
for activation based memory.
So maybe the prefrontal cortex
supports reinforcement learning.
In other words, what is reinforcement learning?
You take an action, you see how much reward you got,
you update your policy of behavior.
Maybe the prefrontal cortex is doing that sort of thing
strictly in its activation patterns.
It’s keeping around a memory in its activity patterns
of what you did, how much reward you got,
and it’s using that activity based memory
as a basis for updating behavior.
But then the question is, well,
how did the prefrontal cortex get so smart?
In other words, where did these activity dynamics come from?
How did that program that’s implemented
in the recurrent dynamics of the prefrontal cortex arise?
And one answer that became evident in this work was,
well, maybe the mechanisms that operate
on the synaptic level, which we believe are mediated
by dopamine, are responsible for shaping those dynamics.
So this may be a silly question,
but because this kind of several temporal sort of classes
of learning are happening and the learning to learnism
emerges, can you keep building stacks of learning
to learn to learn, learning to learn to learn
to learn to learn because it keeps,
I mean, basically abstractions of more powerful abilities
to generalize of learning complex rules.
Yeah, that’s overstretching this kind of mechanism.
Well, one of the people in AI who started thinking
about meta learning from very early on,
Jürgen Schmidhuber sort of cheekily suggested,
I think it may have been in his PhD thesis,
that we should think about meta, meta, meta,
meta, meta, meta learning.
That’s really what’s gonna get us to true intelligence.
Certainly there’s a poetic aspect to it
and it seems interesting and correct
that that kind of levels of abstraction would be powerful,
but is that something you see in the brain?
This kind of, is it useful to think of learning
in these meta, meta, meta way or is it just meta learning?
Well, one thing that really fascinated me
about this mechanism that we were starting to look at,
and other groups started talking
about very similar things at the same time.
And then a kind of explosion of interest
in meta learning happened in the AI community
shortly after that.
I don’t know if we had anything to do with that,
but I was gratified to see that a lot of people
started talking about meta learning.
One of the things that I liked about the kind of flavor
of meta learning that we were studying was that
it didn’t require anything special.
It was just, if you took a system that had
some form of memory that the function of which
could be shaped by pick URL algorithm,
then this would just happen, right?
I mean, there are a lot of forms of,
there are a lot of meta learning algorithms
that have been proposed since then
that are fascinating and effective
in their domains of application.
But they’re engineered, they’re things that somebody
had to say, well, gee, if we wanted meta learning
to happen, how would we do that?
Here’s an algorithm that would,
but there’s something about the kind of meta learning
that we were studying that seemed to me special
in the sense that it wasn’t an algorithm.
It was just something that automatically happened
if you had a system that had memory
and it was trained with a reinforcement learning algorithm.
And in that sense, it can be as meta as it wants to be.
There’s no limit on how abstract the meta learning can get
because it’s not reliant on a human engineering
a particular meta learning algorithm to get there.
And that’s, I also, I don’t know,
I guess I hope that that’s relevant in the brain.
I think there’s a kind of beauty
in the ability of this emergent.
The emergent aspect of it, as opposed to engineered.
Exactly, it’s something that just, it just happens
in a sense, in a sense, you can’t avoid this happening.
If you have a system that has memory
and the function of that memory is shaped
by reinforcement learning, and this system is trained
in a series of interrelated tasks, this is gonna happen.
You can’t stop it.
As long as you have certain properties,
maybe like a recurrent structure to.
You have to have memory.
It actually doesn’t have to be a recurrent neural network.
One of, a paper that I was honored to be involved
with even earlier, used a kind of slot based memory.
Do you remember the title?
Just for people to understand.
It was Memory Augmented Neural Networks.
I think it was, I think the title was
Meta Learning in Memory Augmented Neural Networks.
And it was the same exact story.
If you have a system with memory,
here it was a different kind of memory,
but the function of that memory is shaped
by reinforcement learning.
Here it was the reads and writes that occurred
on this slot based memory.
This will just happen.
But this brings us back to something I was saying earlier
about the importance of the environment.
This will happen if the system is being trained
in a setting where there’s like a sequence of tasks
that all share some abstract structure.
Sometimes we talk about task distributions.
And that’s something that’s very obviously true
of the world that humans inhabit.
Like if you just kind of think about what you do every day,
you never do exactly the same thing
that you did the day before.
But everything that you do sort of has a family resemblance.
It shares a structure with something that you did before.
And so the real world is sort of
saturated with this kind of, this property.
It’s endless variety with endless redundancy.
And that’s the setting in which
this kind of meta learning happens.
And it does seem like we’re just so good at finding,
just like in this emergent phenomena you described,
we’re really good at finding that redundancy,
finding those similarities, the family resemblance.
Some people call it sort of, what is it?
Melanie Mitchell was talking about analogies.
So we’re able to connect concepts together
in this kind of way,
in this same kind of automated emergent way,
which there’s so many echoes here
of psychology and neuroscience.
And obviously now with reinforcement learning
with recurrent neural networks at the core.
If we could talk a little bit about dopamine,
you have really, you’re a part of coauthoring
really exciting recent paper, very recent,
in terms of release on dopamine
and temporal difference learning.
Can you describe the key ideas of that paper?
I mean, one thing I want to pause to do
is acknowledge my coauthors
on actually both of the papers we’re talking about.
So this dopamine paper.
I’ll just, I’ll certainly post all their names.
Yeah, because I’m sort of abashed
to be the spokesperson for these papers
when I had such amazing collaborators on both.
So it’s a comfort to me to know
that you’ll acknowledge them.
Yeah, there’s an incredible team there, but yeah.
Oh yeah, it’s such a, it’s so much fun.
And in the case of the dopamine paper,
we also collaborated with Naochit at Harvard,
who, you know, obviously a paper simply
wouldn’t have happened without him.
But so you were asking for like a thumbnail sketch of.
Yeah, thumbnail sketch or key ideas or, you know,
things, the insights that are, you know,
continuing on our kind of discussion here
between neuroscience and AI.
Yeah, I mean, this was another,
a lot of the work that we’ve done so far
is taking ideas that have bubbled up in AI
and, you know, asking the question of whether the brain
might be doing something related,
which I think on the surface sounds like something
that’s really mainly of use to neuroscience.
We see it also as a way of validating
what we’re doing on the AI side.
If we can gain some evidence that the brain
is using some technique that we’ve been trying out
in our AI work, that gives us confidence
that, you know, it may be a good idea,
that it’ll, you know, scale to rich, complex tasks,
that it’ll interface well with other mechanisms.
So you see it as a two way road.
Yeah, for sure. Just because a particular paper
is a little bit focused on from one to the,
from AI, from neural networks to neuroscience.
Ultimately the discussion, the thinking,
the productive longterm aspect of it
is the two way road nature of the whole interaction.
Yeah, I mean, we’ve talked about the notion
of a virtuous circle between AI and neuroscience.
And, you know, the way I see it,
that’s always been there since the two fields,
you know, jointly existed.
There have been some phases in that history
when AI was sort of ahead.
There are some phases when neuroscience was sort of ahead.
I feel like given the burst of innovation
that’s happened recently on the AI side,
AI is kind of ahead in the sense that
there are all of these ideas that we, you know,
for which it’s exciting to consider
that there might be neural analogs.
And neuroscience, you know,
in a sense has been focusing on approaches
to studying behavior that come from, you know,
that are kind of derived from this earlier era
of cognitive psychology.
And, you know, so in some ways fail to connect
with some of the issues that we’re grappling with in AI.
Like how do we deal with, you know,
large, you know, complex environments.
But, you know, I think it’s inevitable
that this circle will keep turning
and there will be a moment
in the not too different distant future
when neuroscience is pelting AI researchers
with insights that may change the direction of our work.
Just a quick human question.
Is it, you have parts of your brain,
this is very meta, but they’re able to both think
about neuroscience and AI.
You know, I don’t often meet people like that.
So do you think, let me ask a meta plasticity question.
Do you think a human being can be both good at AI
It’s like what, on the team at DeepMind,
what kind of human can occupy these two realms?
And is that something you see everybody should be doing,
can be doing, or is that a very special few
can kind of jump?
Just like we talk about art history,
I would think it’s a special person
that can major in art history
and also consider being a surgeon.
Otherwise known as a dilettante.
A dilettante, yeah.
No, I think it does take a special kind of person
to be truly world class at both AI and neuroscience.
And I am not on that list.
I happen to be someone whose interest in neuroscience
and psychology involved using the kinds
of modeling techniques that are now very central in AI.
And that sort of, I guess, bought me a ticket
to be involved in all of the amazing things
that are going on in AI research right now.
I do know a few people who I would consider
pretty expert on both fronts,
and I won’t embarrass them by naming them,
but there are exceptional people out there
who are like this.
The one thing that I find is a barrier
to being truly world class on both fronts
is just the complexity of the technology
that’s involved in both disciplines now.
So the engineering expertise that it takes
to do truly frontline, hands on AI research
is really, really considerable.
The learning curve of the tools,
just like the specifics of just whether it’s programming
or the kind of tools necessary to collect the data,
to manage the data, to distribute, to compute,
all that kind of stuff.
And on the neuroscience, I guess, side,
there’ll be all different sets of tools.
Exactly, especially with the recent explosion
in neuroscience methods.
So having said all that,
I think the best scenario for both neuroscience
and AI is to have people interacting
who live at every point on this spectrum
from exclusively focused on neuroscience
to exclusively focused on the engineering side of AI.
But to have those people inhabiting a community
where they’re talking to people who live elsewhere
on the spectrum.
And I may be someone who’s very close to the center
in the sense that I have one foot in the neuroscience world
and one foot in the AI world,
and that central position, I will admit,
prevents me, at least someone
with my limited cognitive capacity,
from having true technical expertise in either domain.
But at the same time, I at least hope
that it’s worthwhile having people around
who can kind of see the connections.
Yeah, the community, the emergent intelligence
of the community when it’s nicely distributed is useful.
So hopefully that, I mean, I’ve seen that work,
I’ve seen that work out well at DeepMind.
There are people who, I mean, even if you just focus
on the AI work that happens at DeepMind,
it’s been a good thing to have some people around
doing that kind of work whose PhDs are in neuroscience
Every academic discipline has its kind of blind spots
and kind of unfortunate obsessions and its metaphors
and its reference points,
and having some intellectual diversity is really healthy.
People get each other unstuck, I think.
I see it all the time at DeepMind.
And I like to think that the people
who bring some neuroscience background to the table
are helping with that.
So one of my probably the deepest passion for me,
what I would say, maybe we kind of spoke off mic
a little bit about it, but that I think is a blind spot
for at least robotics and AI folks
is human robot interaction, human agent interaction.
Maybe do you have thoughts about how we reduce the size
of that blind spot?
Do you also share the feeling that not enough folks
are studying this aspect of interaction?
Well, I’m actually pretty intensively interested
in this issue now, and there are people in my group
who’ve actually pivoted pretty hard over the last few years
from doing more traditional cognitive psychology
and cognitive neuroscience to doing experimental work
on human agent interaction.
And there are a couple of reasons that I’m
pretty passionately interested in this.
One is it’s kind of the outcome of having thought
for a few years now about what we’re up to.
Like what are we doing?
Like what is this AI research for?
So what does it mean to make the world a better place?
I think I’m pretty sure that means making life better
And so how do you make life better for humans?
That’s a proposition that when you look at it carefully
and honestly is rather horrendously complicated,
especially when the AI systems
that you’re building are learning systems.
They’re not, you’re not programming something
that you then introduce to the world
and it just works as programmed,
like Google Maps or something.
We’re building systems that learn from experience.
So that typically leads to AI safety questions.
How do we keep these things from getting out of control?
How do we keep them from doing things that harm humans?
And I mean, I hasten to say,
I consider those hugely important issues.
And there are large sectors of the research community
at DeepMind and of course elsewhere
who are dedicated to thinking hard all day,
every day about that.
But there’s, I guess I would say a positive side to this too
which is to say, well, what would it mean
to make human life better?
And how can we imagine learning systems doing that?
And in talking to my colleagues about that,
we reached the initial conclusion
that it’s not sufficient to philosophize about that.
You actually have to take into account
how humans actually work and what humans want
and the difficulties of knowing what humans want
and the difficulties that arise
when humans want different things.
And so human agent interaction has become,
a quite intensive focus of my group lately.
If for no other reason that,
in order to really address that issue in an adequate way,
you have to, I mean, psychology becomes part of the picture.
Yeah, and so there’s a few elements there.
So if you focus on solving like the,
if you focus on the robotics problem,
let’s say AGI without humans in the picture
is you’re missing fundamentally the final step.
When you do want to help human civilization,
you eventually have to interact with humans.
And when you create a learning system, just as you said,
that will eventually have to interact with humans,
the interaction itself has to be become,
has to become part of the learning process.
So you can’t just watch, well, my sense is,
it sounds like your sense is you can’t just watch humans
to learn about humans.
You have to also be part of the human world.
You have to interact with humans.
And I mean, then questions arise that start imperceptibly,
but inevitably to slip beyond the realm of engineering.
So questions like, if you have an agent
that can do something that you can’t do,
under what conditions do you want that agent to do it?
So if I have a robot that can play Beethoven sonatas
better than any human, in the sense that the sensitivity,
the expression is just beyond what any human,
do I want to listen to that?
Do I want to go to a concert and hear a robot play?
These aren’t engineering questions.
These are questions about human preference
and human culture.
Psychology bordering on philosophy.
Yeah, and then you start asking,
well, even if we knew the answer to that,
is it our place as AI engineers
to build that into these agents?
Probably the agents should interact with humans
beyond the population of AI engineers
and figure out what those humans want.
And then when you start,
I referred this the moment ago,
but even that becomes complicated.
Be quote, what if two humans want different things?
And you have only one agent that’s able to interact with them
and try to satisfy their preferences.
Then you’re into the realm of economics
and social choice theory and even politics.
So there’s a sense in which,
if you kind of follow what we’re doing
to its logical conclusion,
then it goes beyond questions of engineering and technology
and starts to shade imperceptibly into questions
about what kind of society do you want?
And actually, once that dawned on me,
I actually felt,
I don’t know what the right word is,
quite refreshed in my involvement in AI research.
It was almost like building this kind of stuff
is gonna lead us back to asking really fundamental questions
about what is this,
what’s the good life and who gets to decide
and bringing in viewpoints from multiple sub communities
to help us shape the way that we live.
There’s something, it started making me feel like
doing AI research in a fully responsible way, would,
could potentially lead to a kind of like cultural renewal.
Yeah, it’s the way to understand human beings
at the individual, at the societal level.
It may become a way to answer all the silly human questions
of the meaning of life and all those kinds of things.
Even if it doesn’t give us a way
of answering those questions,
it may force us back to thinking about them.
And it might bring, it might restore a certain,
I don’t know, a certain depth to,
or even dare I say spirituality to the way that,
to the world, I don’t know.
Maybe that’s too grandiose.
Well, I’m with you.
I think it’s AI will be the philosophy of the 21st century,
the way which will open the door.
I think a lot of AI researchers are afraid to open that door
of exploring the beautiful richness
of the human agent interaction, human AI interaction.
I’m really happy that somebody like you
have opened that door.
And one thing I often think about is the usual schema
for thinking about human agent interaction
as this kind of dystopian, oh, our robot overlords.
And again, I hasten to say AI safety is hugely important.
And I’m not saying we shouldn’t be thinking
about those risks, totally on board for that.
But there’s, having said that,
what often follows for me is the thought
that there’s another kind of narrative
that might be relevant, which is,
when we think of humans gaining more and more information
about human life, the narrative there is usually
that they gain more and more wisdom
and they get closer to enlightenment
and they become more benevolent.
And the Buddha is like, that’s a totally different narrative.
And why isn’t it the case that we imagine
that the AI systems that we’re creating
are just gonna, like, they’re gonna figure out
more and more about the way the world works
and the way that humans interact
and they’ll become beneficent.
I’m not saying that will happen.
I don’t honestly expect that to happen
without some careful, setting things up very carefully.
But it’s another way things could go, right?
And yeah, and I would even push back on that.
I personally believe that the most trajectories,
natural human trajectories will lead us towards progress.
So for me, there is a kind of sense
that most trajectories in AI development
will lead us into trouble.
To me, and we over focus on the worst case.
It’s like in computer science,
theoretical computer science has been this focus
on worst case analysis.
There’s something appealing to our human mind
at some lowest level to be good.
I mean, we don’t wanna be eaten by the tiger, I guess.
So we wanna do the worst case analysis.
But the reality is that shouldn’t stop us
from actually building out all the other trajectories
which are potentially leading to all the positive worlds,
all the enlightenment.
There’s a book, Enlightenment Now,
with Steven Pinker and so on.
This is looking generally at human progress.
And there’s so many ways that human progress
can happen with AI.
And I think you have to do that research.
You have to do that work.
You have to do the, not just the AI safety work
of the one worst case analysis.
How do we prevent that?
But the actual tools and the glue
and the mechanisms of human AI interaction
that would lead to all the positive actions that can go.
It’s a super exciting area, right?
Yeah, we should be spending,
we should be spending a lot of our time saying
what can go wrong.
I think it’s harder to see that there’s work to be done
to bring into focus the question of what it would look like
for things to go right.
That’s not obvious.
And we wouldn’t be doing this if we didn’t have the sense
there was huge potential, right?
We’re not doing this for no reason.
We have a sense that AGI would be a major boom to humanity.
But I think it’s worth starting now,
even when our technology is quite primitive,
asking exactly what would that mean?
We can start now with applications
that are already gonna make the world a better place,
like solving protein folding.
I think DeepMind has gotten heavy
into science applications lately,
which I think is a wonderful, wonderful move
for us to be making.
But when we think about AGI,
when we think about building fully intelligent
agents that are gonna be able to, in a sense,
do whatever they want,
we should start thinking about
what do we want them to want, right?
What kind of world do we wanna live in?
That’s not an easy question.
And I think we just need to start working on it.
And even on the path to,
it doesn’t have to be AGI,
but just intelligent agents that interact with us
and help us enrich our own existence on social networks,
for example, on recommender systems of various intelligence.
And there’s so much interesting interaction
that’s yet to be understood and studied.
And how do you create,
I mean, Twitter is struggling with this very idea,
how do you create AI systems
that increase the quality and the health of a conversation?
That’s a beautiful human psychology question.
And how do you do that
without deception being involved,
without manipulation being involved,
maximizing human autonomy?
And how do you make these choices in a democratic way?
How do we face the,
again, I’m speaking for myself here.
How do we face the fact that
it’s a small group of people
who have the skillset to build these kinds of systems,
but what it means to make the world a better place
is something that we all have to be talking about.
Yeah, the world that we’re trying to make a better place
includes a huge variety of different kinds of people.
Yeah, how do we cope with that?
This is a problem that has been discussed
in gory, extensive detail in social choice theory.
One thing I’m really interested in
and one thing I’m really enjoying
about the recent direction work has taken
in some parts of my team is that,
yeah, we’re reading the AI literature,
we’re reading the neuroscience literature,
but we’ve also started reading economics
and, as I mentioned, social choice theory,
even some political theory,
because it turns out that it all becomes relevant.
It all becomes relevant.
But at the same time,
we’ve been trying not to write philosophy papers,
we’ve been trying not to write physician papers.
We’re trying to figure out ways
of doing actual empirical research
that kind of take the first small steps
to thinking about what it really means
for humans with all of their complexity
and contradiction and paradox
to be brought into contact with these AI systems
in a way that really makes the world a better place.
Often, reinforcement learning frameworks
actually kind of allow you to do that,
machine learning, and so that’s the exciting thing about AI
is it allows you to reduce the unsolvable problem,
philosophical problem, into something more concrete
that you can get ahold of.
Yeah, and it allows you to kind of define the problem
in some way that allows for growth in the system
that’s sort of, you know,
you’re not responsible for the details, right?
You say, this is generally what I want you to do,
and then learning takes care of the rest.
Of course, the safety issues arise in that context,
but I think also some of these positive issues
arise in that context.
What would it mean for an AI system
to really come to understand what humans want?
And with all of the subtleties of that, right?
You know, humans want help with certain things,
but they don’t want everything done for them, right?
There is, part of the satisfaction
that humans get from life is in accomplishing things.
So if there were devices around that did everything for,
you know, I often think of the movie WALLI, right?
That’s like dystopian in a totally different way.
It’s like, the machines are doing everything for us.
That’s not what we wanted.
You know, anyway, I find this, you know,
this opens up a whole landscape of research
that feels affirmative and exciting.
To me, it’s one of the most exciting, and it’s wide open.
We have to, because it’s a cool paper,
talk about dopamine.
Oh yeah, okay, so I can.
We were gonna, I was gonna give you a quick summary.
Yeah, a quick summary of, what’s the title of the paper?
I think we called it a distributional code for value
in dopamine based reinforcement learning, yes.
So that’s another project that grew out of pure AI research.
A number of people at DeepMind and a few other places
had started working on a new version
of reinforcement learning,
which was defined by taking something
in traditional reinforcement learning and just tweaking it.
So the thing that they took
from traditional reinforcement learning was a value signal.
So at the center of reinforcement learning,
at least most algorithms, is some representation
of how well things are going,
your expected cumulative future reward.
And that’s usually represented as a single number.
So if you imagine a gambler in a casino
and the gambler’s thinking, well, I have this probability
of winning such and such an amount of money,
and I have this probability of losing such and such
an amount of money, that situation would be represented
as a single number, which is like the expected,
the weighted average of all those outcomes.
And this new form of reinforcement learning said,
well, what if we generalize that
to a distributional representation?
So now we think of the gambler as literally thinking,
well, there’s this probability
that I’ll win this amount of money,
and there’s this probability
that I’ll lose that amount of money,
and we don’t reduce that to a single number.
And it had been observed through experiments,
through just trying this out,
that that kind of distributional representation
really accelerated reinforcement learning
and led to better policies.
What’s your intuition about,
so we’re talking about rewards.
So what’s your intuition why that is, why does it do that?
Well, it’s kind of a surprising historical note,
at least surprised me when I learned it,
that this had been proven to be true.
This had been tried out in a kind of heuristic way.
People thought, well, gee, what would happen if we tried?
And then it had this, empirically,
it had this striking effect.
And it was only then that people started thinking,
well, gee, wait, why?
Why is this working?
And that’s led to a series of studies
just trying to figure out why it works, which is ongoing.
But one thing that’s already clear from that research
is that one reason that it helps
is that it drives richer representation learning.
So if you imagine two situations
that have the same expected value,
the same kind of weighted average value,
standard deep reinforcement learning algorithms
are going to take those two situations
and kind of, in terms of the way
they’re represented internally,
they’re gonna squeeze them together
because the thing that you’re trying to represent,
which is their expected value, is the same.
So all the way through the system,
things are gonna be mushed together.
But what if those two situations
actually have different value distributions?
They have the same average value,
but they have different distributions of value.
In that situation, distributional learning
will maintain the distinction between these two things.
So to make a long story short,
distributional learning can keep things separate
in the internal representation
that might otherwise be conflated or squished together.
And maintaining those distinctions
can be useful when the system is now faced
with some other task where the distinction is important.
If we look at the optimistic
and pessimistic dopamine neurons.
So first of all, what is dopamine?
Why is this at all useful
to think about in the artificial intelligence sense?
But what do we know about dopamine in the human brain?
What is it?
Why is it useful?
Why is it interesting?
What does it have to do with the prefrontal cortex
and learning in general?
Yeah, so, well, this is also a case
where there’s a huge amount of detail and debate.
But one currently prevailing idea
is that the function of this neurotransmitter dopamine
resembles a particular component
of standard reinforcement learning algorithms,
which is called the reward prediction error.
So I was talking a moment ago
about these value representations.
How do you learn them?
How do you update them based on experience?
Well, if you made some prediction about a future reward
and then you get more reward than you were expecting,
then probably retrospectively,
you want to go back and increase the value representation
that you attached to that earlier situation.
If you got less reward than you were expecting,
you should probably decrement that estimate.
And that’s the process of temporal difference.
Exactly, this is the central mechanism
of temporal difference learning,
which is one of several sort of the backbone
of our momentarium in NRL.
And this connection between the reward prediction error
and dopamine was made in the 1990s.
And there’s been a huge amount of research
that seems to back it up.
Dopamine may be doing other things,
but this is clearly, at least roughly,
one of the things that it’s doing.
But the usual idea was that dopamine
was representing these reward prediction errors,
again, in this like kind of single number way
that representing your surprise with a single number.
And in distributional reinforcement learning,
this kind of new elaboration of the standard approach,
it’s not only the value function
that’s represented as a single number,
it’s also the reward prediction error.
And so what happened was that Will Dabney,
one of my collaborators who was one of the first people
to work on distributional temporal difference learning,
talked to a guy in my group, Zeb Kurt Nelson,
who’s a computational neuroscientist,
and said, gee, you know, is it possible
that dopamine might be doing something
like this distributional coding thing?
And they started looking at what was in the literature,
and then they brought me in,
and we started talking to Nao Uchida,
and we came up with some specific predictions
about if the brain is using
this kind of distributional coding,
then in the tasks that Nao has studied,
you should see this, this, this, and this,
and that’s where the paper came from.
We kind of enumerated a set of predictions,
all of which ended up being fairly clearly confirmed,
and all of which leads to at least some initial indication
that the brain might be doing something
like this distributional coding,
that dopamine might be representing surprise signals
in a way that is not just collapsing everything
to a single number, but instead is kind of respecting
the variety of future outcomes, if that makes sense.
So yeah, so that’s showing, suggesting possibly
that dopamine has a really interesting
representation scheme in the human brain
for its reward signal.
Exactly. That’s fascinating.
That’s another beautiful example of AI
revealing something nice about neuroscience,
potentially suggesting possibilities.
Well, you never know.
So the minute you publish a paper like that,
the next thing you think is, I hope that replicates.
Like, I hope we see that same thing in other data sets,
but of course, several labs now
are doing the followup experiments, so we’ll know soon.
But it has been a lot of fun for us
to take these ideas from AI
and kind of bring them into neuroscience
and see how far we can get.
So we kind of talked about it a little bit,
but where do you see the field of neuroscience
and artificial intelligence heading broadly?
Like, what are the possible exciting areas
that you can see breakthroughs in the next,
let’s get crazy, not just three or five years,
but the next 10, 20, 30 years
that would make you excited
and perhaps you’d be part of?
On the neuroscience side,
there’s a great deal of interest now
in what’s going on in AI.
And at the same time,
I feel like, so neuroscience,
especially the part of neuroscience
that’s focused on circuits and systems,
kind of like really mechanism focused,
there’s been this explosion in new technology.
And up until recently,
the experiments that have exploited this technology
have not involved a lot of interesting behavior.
And this is for a variety of reasons,
one of which is in order to employ
some of these technologies,
you actually have to, if you’re studying a mouse,
you have to head fix the mouse.
In other words, you have to like immobilize the mouse.
And so it’s been tricky to come up
with ways of eliciting interesting behavior
from a mouse that’s restrained in this way,
but people have begun to create
very interesting solutions to this,
like virtual reality environments
where the animal can kind of move a track ball.
And as people have kind of begun to explore
what you can do with these technologies,
I feel like more and more people are asking,
well, let’s try to bring behavior into the picture.
Let’s try to like reintroduce behavior,
which was supposed to be what this whole thing was about.
And I’m hoping that those two trends,
the kind of growing interest in behavior
and the widespread interest in what’s going on in AI,
will come together to kind of open a new chapter
in neuroscience research where there’s a kind of
a rebirth of interest in the structure of behavior
and its underlying substrates,
but that that research is being informed
by computational mechanisms
that we’re coming to understand in AI.
If we can do that, then we might be taking a step closer
to this utopian future that we were talking about earlier
where there’s really no distinction
between psychology and neuroscience.
Neuroscience is about studying the mechanisms
that underlie whatever it is the brain is for,
and what is the brain for?
What is the brain for? It’s for behavior.
I feel like we could maybe take a step toward that now
if people are motivated in the right way.
You also asked about AI.
So that was a neuroscience question.
You said neuroscience, that’s right.
And especially places like DeepMind
are interested in both branches.
So what about the engineering of intelligence systems?
I think one of the key challenges
that a lot of people are seeing now in AI
is to build systems that have the kind of flexibility
and the kind of flexibility that humans have in two senses.
One is that humans can be good at many things.
They’re not just expert at one thing.
And they’re also flexible in the sense
that they can switch between things very easily
and they can pick up new things very quickly
because they very ably see what a new task has in common
with other things that they’ve done.
And that’s something that our AI systems
just blatantly do not have.
There are some people who like to argue
that deep learning and deep RL
are simply wrong for getting that kind of flexibility.
I don’t share that belief,
but the simpler fact of the matter
is we’re not building things yet
that do have that kind of flexibility.
And I think the attention of a large part
of the AI community is starting to pivot to that question.
How do we get that?
That’s gonna lead to a focus on abstraction.
It’s gonna lead to a focus on
what in psychology we call cognitive control,
which is the ability to switch between tasks,
the ability to quickly put together a program of behavior
that you’ve never executed before,
but you know makes sense for a particular set of demands.
It’s very closely related to what the prefrontal cortex does
on the neuroscience side.
So I think it’s gonna be an interesting new chapter.
So that’s the reasoning side and cognition side,
but let me ask the over romanticized question.
Do you think we’ll ever engineer an AGI system
that we humans would be able to love
and that would love us back?
So have that level and depth of connection?
I love that question.
And it relates closely to things
that I’ve been thinking about a lot lately,
in the context of this human AI research.
There’s social psychology research
in particular by Susan Fisk at Princeton
the department where I used to work,
where she dissects human attitudes toward other humans
into a sort of two dimensional scheme.
And one dimension is about ability.
How able, how capable is this other person?
But the other dimension is warmth.
So you can imagine another person who’s very skilled
and capable, but is very cold.
And you wouldn’t really like highly,
you might have some reservations about that other person.
But there’s also a kind of reservation
that we might have about another person
who elicits in us or displays a lot of human warmth,
but is not good at getting things done.
We reserve our greatest esteem really
for people who are both highly capable
and also quite warm.
That’s like the best of the best.
This isn’t a normative statement I’m making.
This is just an empirical statement.
This is what humans seem…
These are the two dimensions that people seem to kind of like
along which people size other people up.
And in AI research,
there’s a lot of people who think that humans are
very capable, and in AI research,
we really focus on this capability thing.
We want our agents to be able to do stuff.
This thing can play go at a superhuman level.
But that’s only one dimension.
What about the other dimension?
What would it mean for an AI system to be warm?
And I don’t know, maybe there are easy solutions here.
Like we can put a face on our AI systems.
It’s cute, it has big ears.
I mean, that’s probably part of it.
But I think it also has to do with a pattern of behavior.
A pattern of what would it mean for an AI system
to display caring, compassionate behavior
in a way that actually made us feel like it was for real?
That we didn’t feel like it was simulated.
We didn’t feel like we were being duped.
To me, people talk about the Turing test
or some descendant of it.
I feel like that’s the ultimate Turing test.
Is there an AI system that can not only convince us
that it knows how to reason
and it knows how to interpret language,
but that we’re comfortable saying,
yeah, that AI system’s a good guy.
On the warmth scale, whatever warmth is,
we kind of intuitively understand it,
but we also wanna be able to, yeah,
we don’t understand it explicitly enough yet
to be able to engineer it.
And that’s an open scientific question.
You kind of alluded it several times
in the human AI interaction.
That’s a question that should be studied
and probably one of the most important questions
as we move to AGI.
We humans are so good at it.
It’s not just that we’re born warm.
I suppose some people are warmer than others
given whatever genes they manage to inherit.
But there are also learned skills involved.
There are ways of communicating to other people
that you care, that they matter to you,
that you’re enjoying interacting with them, right?
And we learn these skills from one another.
And it’s not out of the question
that we could build engineered systems.
I think it’s hopeless, as you say,
that we could somehow hand design
these sorts of behaviors.
But it’s not out of the question
that we could build systems that kind of,
we instill in them something that sets them out
in the right direction,
so that they end up learning what it is
to interact with humans
in a way that’s gratifying to humans.
I mean, honestly, if that’s not where we’re headed,
I want out.
I think it’s exciting as a scientific problem,
just as you described.
I honestly don’t see a better way to end it
than talking about warmth and love.
And Matt, I don’t think I’ve ever had such a wonderful
conversation where my questions were so bad
and your answers were so beautiful.
So I deeply appreciate it.
I really enjoyed it.
Thanks for talking to me.
Well, it’s been very fun.
As you can probably tell,
there’s something I like about kind of thinking
outside the box and like,
so it’s good having an opportunity to do that.
Thanks so much for doing it.
Thanks for listening to this conversation
with Matt Bopenik.
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Again, spelled miraculously without the E,
just F R I D M A N.
And now let me leave you with some words
from neurologist V.S. Amarachandran.
How can a three pound mass of jelly
that you can hold in your palm imagine angels,
contemplate the meaning of an infinity
and even question its own place in the cosmos?
Especially awe inspiring is the fact that any single brain,
including yours, is made up of atoms
that were forged in the hearts
of countless far flung stars billions of years ago.
These particles drifted for eons and light years
until gravity and change brought them together here now.
These atoms now form a conglomerate, your brain,
that can not only ponder the very stars they gave at birth,
but can also think about its own ability to think
and wonder about its own ability to wander.
With the arrival of humans, it has been said,
the universe has suddenly become conscious of itself.
This truly is the greatest mystery of all.
Thank you for listening and hope to see you next time.