What difference between biological neural networks and artificial neural networks
is most mysterious, captivating and profound for you?
First of all, there's so much we don't know about biological neural networks,
and that's very mysterious and captivating because maybe it holds the key to improving
artificial neural networks. One of the things I studied recently is something that
we don't know how biological neural networks do, but would be really useful for artificial ones,
is the ability to do credit assignment through very long time spans.
There are things that we can in principle do with artificial neural nets, but it's not very
convenient and it's not biologically plausible. And this mismatch, I think this kind of mismatch,
maybe an interesting thing to study, to A, understand better how brains might do these
things because we don't have good corresponding theories with artificial neural nets, and B,
maybe provide new ideas that we could explore about things that brain do differently and
that we could incorporate in artificial neural nets.
So let's break credit assignment up a little bit. So what? It's a beautifully technical term,
but it could incorporate so many things. So is it more on the RNN memory side,
thinking like that, or is it something about knowledge, building up common sense knowledge
over time, or is it more in the reinforcement learning sense that you're picking up rewards
over time for a particular to achieve a certain kind of goal?
So I was thinking more about the first two meanings whereby we store all kinds of memories,
episodic memories in our brain, which we can access later in order to help us both infer
causes of things that we are observing now and assign credit to decisions or interpretations
we came up with a while ago when those memories were stored. And then we can change the way we
would have reacted or interpreted things in the past, and now that's credit assignment used for learning.
So in which way do you think artificial neural networks, the current LSTM,
the current architectures are not able to capture the presumably you're thinking of very long term?
Yes. So current, the current nets are doing a fairly good jobs for sequences with dozens or say
hundreds of time steps. And then it gets sort of harder and harder and depending on what you
have to remember and so on as you consider longer durations. Whereas humans seem to be able to
do credit assignment through essentially arbitrary times like I could remember something I did last
year. And then now because I see some new evidence, I'm going to change my mind about
the way I was thinking last year, and hopefully not do the same mistake again.
I think a big part of that is probably forgetting. You're only remembering the really important
things that's very efficient forgetting. Yes. So there's a selection of what we remember.
And I think there are really cool connection to higher level cognitions here regarding
consciousness, deciding and emotions. So deciding what comes to consciousness and what gets stored
in memory, which are not trivial either. So you've been at the forefront there all along
showing some of the amazing things that neural networks, deep neural networks can do in the
field of artificial intelligence is just broadly in all kinds of applications. But we can talk
about that forever. But what in your view, because we're thinking towards the future is the weakest
aspect of the way deep neural networks represent the world. What is that? What is in your view
is missing? So current state of the art neural nets trained on large quantities of images or texts
have some level of understanding of what explains those data sets, but it's very
basic. It's very low level. And it's not nearly as robust and abstract and general as our understanding.
Okay, so that doesn't tell us how to fix things. But I think it encourages us to think about
how we can maybe train our neural nets differently, so that they would focus, for example, on causal
explanations, something that we don't do currently with neural net training. Also, one thing I'll
talk about in my talk this afternoon is instead of learning separately from images and videos on
one hand and from texts on the other hand, we need to do a better job of jointly learning about
language and about the world to which it refers. So that, you know, both sides can help each other.
We need to have good world models in our neural nets for them to really understand sentences
which talk about what's going on in the world. And I think we need language input to help
provide clues about what high level concepts like semantic concepts should be represented
at the top levels of these neural nets. In fact, there is evidence that the purely unsupervised
learning of representations doesn't give rise to high level representations that are as powerful
as the ones we're getting from supervised learning. And so the clues we're getting just with the labels,
not even sentences, is already very powerful. Do you think that's an architecture challenge
or is it a data set challenge? Neither. I'm tempted to just end it there.
Of course, data sets and architectures are something you want to always play with. But
I think the crucial thing is more the training objectives, the training frameworks. For example,
going from passive observation of data to more active agents, which
learn by intervening in the world, the relationships between causes and effects,
the sort of objective functions which could be important to allow the highest level
of explanations to rise from the learning, which I don't think we have now. The kinds of
objective functions which could be used to reward exploration, the right kind of exploration. So
these kinds of questions are neither in the data set nor in the architecture, but more in
how we learn under what objectives and so on. Yeah, that's a, I've heard you mention in several
contexts, the idea of sort of the way children learn, they interact with objects in the world.
And it seems fascinating because in some sense, except with some cases in reinforcement learning,
that idea is not part of the learning process in artificial neural networks. It's almost like
do you envision something like an objective function saying, you know what, if you poke this
object in this kind of way, it would be really helpful for me to further, further learn.
Sort of almost guiding some aspect of learning. Right, right, right. So I was talking to Rebecca
Sachs just an hour ago and she was talking about lots and lots of evidence from infants seem to
clearly pick what interests them in a directed way. And so they're not passive learners.
They, they focus their attention on aspects of the world, which are most interesting,
surprising in a non trivial way that makes them change their theories of the world.
So that's a fascinating view of the future progress. But on a more maybe boring question,
do you think going deeper and larger? So do you think just increasing the size of the things
that have been increasing a lot in the past few years will, will also make significant progress?
So some of the representational issues that you, you mentioned, they're kind of shallow
in some sense. Oh, you mean in the sense of abstraction,
abstract in the sense of abstraction, they're not getting some, I don't think that having
more depth in the network in the sense of instead of 100 layers, we have 10,000 is going to solve
our problem. You don't think so? Is that obvious to you? Yes. What is clear to me is that
engineers and companies and labs, grad students will continue to tune architectures and explore
all kinds of tweaks to make the current state of the art slightly ever slightly better. But
I don't think that's going to be nearly enough. I think we need some fairly drastic changes in
the way that we're considering learning to achieve the goal that these learners actually
understand in a deep way the environment in which they are, you know, observing and acting.
But I guess I was trying to ask a question that's more interesting than just more layers
is basically once you figure out a way to learn through interacting, how many parameters does
it take to store that information? So I think our brain is quite bigger than most neural networks.
Right, right. Oh, I see what you mean. Oh, I'm with you there. So I agree that in order to
build neural nets with the kind of broad knowledge of the world that typical adult humans have,
probably the kind of computing power we have now is going to be insufficient.
So the good news is there are hardware companies building neural net chips. And so
it's going to get better. However, the good news in a way, which is also a bad news, is that even
our state of the art deep learning methods fail to learn models that understand even very simple
environments like some grid worlds that we have built. Even these fairly simple environments,
I mean, of course, if you train them with enough examples, eventually they get it,
but it's just like instead of what humans might need just dozens of examples, these things will
need millions, right, for very, very, very simple tasks. And so I think there's an opportunity
for academics who don't have the kind of computing power that say Google has
to do really important and exciting research to advance the state of the art in training
frameworks, learning models, agent learning in even simple environments that are synthetic,
that seem trivial, but yet current machine learning fails on.
We talked about priors and common sense knowledge. It seems like we humans take a lot of knowledge
for granted. So what's your view of these priors of forming this broad view of the world, this
accumulation of information, and how we can teach neural networks or learning systems to pick that
knowledge up? So knowledge, you know, for a while, the artificial intelligence, maybe in the 80,
like there's a time where knowledge representation, knowledge, acquisition, expert systems, I mean,
though, the symbolic AI was a view, was an interesting problem set to solve. And it was kind
of put on hold a little bit, it seems like because it doesn't work. It doesn't work. That's right.
But that's right. But the goals of that remain important. Yes, remain important. And how do you
think those goals can be addressed? Right. So first of all, I believe that one reason why the
classical expert systems approach failed is because a lot of the knowledge we have, so you talked
about common sense and tuition, there's a lot of knowledge like this, which is not consciously
accessible. There are lots of decisions we're taking that we can't really explain, even if
sometimes we make up a story. And that knowledge is also necessary for machines to take good
decisions. And that knowledge is hard to codify in expert systems, rule based systems, and, you
know, classical AI formalism. And there are other issues, of course, with the old AI, like,
not really good ways of handling uncertainty, I would say something more subtle,
which we understand better now, but I think still isn't enough in the minds of people.
There's something really powerful that comes from distributed representations, the thing that really
makes neural nets work so well. And it's hard to replicate that kind of power in a symbolic world.
The knowledge in expert systems and so on is nicely decomposed into like a bunch of rules.
Whereas if you think about a neural net, it's the opposite. You have this big blob of parameters
which work intensely together to represent everything the network knows. And it's not
sufficiently factorized. And so I think this is one of the weaknesses of current neural nets,
that we have to take lessons from classical AI in order to bring in another kind of
compositionality, which is common in language, for example, and in these rules. But that isn't
so native to neural nets. And on that line of thinking, disentangled representations. Yes. So
let me connect with disentangled representations. If you might, if you don't mind. Yes, exactly.
Yeah. So for many years, I thought, and I still believe that it's really important that we come
up with learning algorithms, either unsupervised or supervised, but reinforcement, whatever,
that build representations in which the important factors, hopefully causal factors are nicely
separated and easy to pick up from the representation. So that's the idea of disentangled
representations. It says transfer the data into a space where everything becomes easy, we can maybe
just learn with linear models about the things we care about. And I still think this is important,
but I think this is missing out on a very important ingredient, which classical AI systems can remind
us of. So let's say we have these disentangled representations, you still need to learn about
the, the relationships between the variables, those high level semantic variables, they're not
going to be independent. I mean, this is like too much of an assumption. They're going to have some
interesting relationships that allow to predict things in the future to explain what happened in
the past. The kind of knowledge about those relationships in a classical AI system is
encoded in the rules, like a rule is just like a little piece of knowledge that says, oh, I have
these two, three, four variables that are linked in this interesting way. Then I can say something
about one or two of them given a couple of others, right? In addition to disentangling the,
the elements of the representation, which are like the variables in a rule based system,
you also need to disentangle the, the mechanisms that relate those variables to each other.
So like the rules. So if the rules are neatly separated, like each rule is, you know, living
on its own. And when I, I change a rule because I'm learning, it doesn't need to break other rules.
Whereas current neural nets, for example, are very sensitive to what's called catastrophic
forgetting, where after I've learned some things, and then they learn new things, they can destroy
the old things that I had learned, right? If the knowledge was better factorized and, and
and separated disentangled, then you would avoid a lot of that. Now you can't do this in the
sensory domain, but my idea in like a pixel space, but, but my idea is that when you project the
data in the right semantic space, it becomes possible to now represent this extra knowledge
beyond the transformation from input to representations, which is how representations
act on each other and predict the future and so on, in a way that can be neatly
disentangled. So now it's the rules that are disentangled from each other and not just the
variables that are disentangled from each other. And you draw distinction between semantic space
and pixel, like, does there need to be an architectural difference? Well, yeah. So, so
there's the sensory space like pixels, which where everything is entangled,
and the information, like the variables are completely interdependent in very complicated
ways. And also computation, like the, it's not just variables, it's also how they are
related to each other is, is all intertwined. But, but I'm hypothesizing that in the right
high level representation space, both the variables and how they relate to each other
can be disentangled and that will provide a lot of generalization power. Generalization power.
Yes. Distribution of the test set, it's assumed to be the same as a distribution of the training
set. Right. This is where current machine learning is too weak. It doesn't tell us anything,
is not able to tell us anything about how our neural nets, say, are going to generalize to a
new distribution. And, and, you know, people may think, well, but there's nothing we can say if
we don't know what the new distribution will be. The truth is, humans are able to generalize to
new distributions. Yeah, how are we able to do that? So yeah, because there is something, these
new distributions, even though they could look very different from the training distributions,
they have things in common. So let me give you a concrete example. You read a science fiction
novel, the science fiction novel, maybe, you know, brings you in some other planet where
things look very different on the surface, but it's still the same laws of physics.
All right. And so you can read the book and you understand what's going on.
So the distribution is very different. But because you can transport a lot of the knowledge you had
from Earth about the underlying cause and effect relationships and physical mechanisms and all
that, and maybe even social interactions, you can now make sense of what is going on on this
planet where like visually, for example, things are totally different.
Taking that analogy further and distorting it, let's enter a science fiction world of, say,
Space Odyssey 2001 with Hal. Yeah. Or maybe, which is probably one of my favorite AI movies.
Me too. And then there's another one that a lot of people love that may be a little bit outside
of the AI community is Ex Machina. I don't know if you've seen it. Yes. By the way, what are your
reviews on that movie? Are you able to enjoy it? So there are things I like and things I hate.
So let me, you could talk about that in the context of a question I want to ask,
which is there's quite a large community of people from different backgrounds off and outside of AI
who are concerned about existential threat of artificial intelligence. Right. You've seen
now this community develop over time. You've seen you have a perspective. So what do you think is
the best way to talk about AI safety, to think about it, to have discourse about it within AI
community and outside and grounded in the fact that Ex Machina is one of the main sources of
information for the general public about AI. So I think you're putting it right. There's a big
difference between the sort of discussion we ought to have within the AI community
and the sort of discussion that really matter in the general public. So I think the picture of
Terminator and, you know, AI loose and killing people and super intelligence that's going to
destroy us, whatever we try, isn't really so useful for the public discussion because
for the public discussion that things I believe really matter are the short term and
mini term, very likely negative impacts of AI on society, whether it's from security,
like, you know, big brother scenarios with face recognition or killer robots, or the impact on
the job market, or concentration of power and discrimination, all kinds of social issues,
which could actually, some of them could really threaten democracy, for example.
Just to clarify, when you said killer robots, you mean autonomous weapons as a weapon system?
Yes, I don't mean, no, that's right. So I think these short and medium term concerns
should be important parts of the public debate. Now, existential risk, for me, is a very unlikely
consideration, but still worth academic investigation. In the same way that you could say,
should we study what could happen if meteorite, you know, came to earth and destroyed it.
So I think it's very unlikely that this is going to happen in or happen in a reasonable future.
It's very, the sort of scenario of an AI getting loose goes against my understanding of at least
current machine learning and current neural nets and so on. It's not plausible to me.
But of course, I don't have a crystal ball and who knows what AI will be in 50 years from now.
So I think it is worth that scientists study those problems. It's just not a pressing question,
as far as I'm concerned. So before I continue down that line, I have a few questions there, but
what do you like and not like about X Machina as a movie? Because I actually watched it for the
second time and enjoyed it. I hated it the first time and I enjoyed it quite a bit more the second
time when I sort of learned to accept certain pieces of it. See it as a concept movie. What
was your experience? What were your thoughts? So the negative is the picture it paints of science
is totally wrong. Science in general and AI in particular. Science is not happening
in some hidden place by some really smart guy. One person. One person. This is totally unrealistic.
This is not how it happens. Even a team of people in some isolated place will not make it.
Science moves by small steps thanks to the collaboration and community of a large number
of people interacting and all the scientists who are expert in their field kind of know what is
going on even in the industrial labs. Information flows and leaks and so on. And the spirit of
it is very different from the way science is painted in this movie. Yeah, let me ask on that
point. It's been the case to this point that kind of even if the research happens inside
Google or Facebook, inside companies, it still kind of comes out. Do you think that will always be
the case with AI? Is it possible to bottle ideas to the point where there's a set of breakthroughs
that go completely undiscovered by the general research community? Do you think that's even
possible? It's possible, but it's unlikely. It's not how it is done now. It's not how I can force
it in in the foreseeable future. But of course, I don't have a crystal ball. And so who knows,
this is science fiction after all. But but usually ominous that the lights went off during
during that discussion. So the problem again, there's a you know, one thing is the movie and
you could imagine all kinds of science fiction. The problem with for me, maybe similar to the
question about existential risk is that this kind of movie paints such a wrong picture of what is
actual, you know, the actual science and how it's going on that that it can have unfortunate effects
on people's understanding of current science. And so that's kind of sad.
There's an important principle in research, which is diversity. So in other words,
research is exploration, research is exploration in the space of ideas. And different people
will focus on different directions. And this is not just good, it's essential. So I'm totally fine
with people exploring directions that are contrary to mine or look orthogonal to mine.
I am more than fine, I think it's important. I and my friends don't claim we have universal
truth about what will especially about what will happen in the future. Now that being said,
we have our intuitions and then we act accordingly, according to where we think we can be most useful
and where society has the most to gain or to lose. We should have those debates and
and not end up in a society where there's only one voice and one way of thinking and
research money is spread out. So this agreement is a sign of good research, good science. So
yes. The idea of bias in the human sense of bias. How do you think about instilling in machine
learning something that's aligned with human values in terms of bias? We intuitively assume
beings have a concept of what bias means, of what fundamental respect for other human beings means,
but how do we instill that into machine learning systems, do you think?
So I think there are short term things that are already happening and then there are long term
things that we need to do. In the short term, there are techniques that have been proposed and
I think will continue to be improved and maybe alternatives will come up to take data sets
in which we know there is bias, we can measure it. Pretty much any data set where humans are
being observed taking decisions will have some sort of bias discrimination against particular
groups and so on. And we can use machine learning techniques to try to build predictors, classifiers
that are going to be less biased. We can do it for example using adversarial methods to make our
systems less sensitive to these variables we should not be sensitive to. So these are clear,
well defined ways of trying to address the problem, maybe they have weaknesses and more
research is needed and so on, but I think in fact they're sufficiently mature that governments should
start regulating companies where it matters say like insurance companies so that they use those
techniques because those techniques will probably reduce the bias, but at a cost for example maybe
their predictions will be less accurate and so companies will not do it until you force them.
All right, so this is short term. Long term, I'm really interested in thinking how we can
instill moral values into computers. Obviously this is not something we'll achieve in the next five
or 10 years. There's already work in detecting emotions for example in images and sounds and
texts and also studying how different agents interacting in different ways may correspond to
patterns of say injustice which could trigger anger. So these are things we can do in the
medium term and eventually train computers to model for example how humans react emotionally. I would
say the simplest thing is unfair situations which trigger anger. This is one of the most basic
emotions that we share with other animals. I think it's quite feasible within the next few years so
we can build systems that can detect these kind of things to the extent unfortunately that they
understand enough about the world around us which is a long time away but maybe we can initially do
this in virtual environments so you can imagine like a video game where agents interact in some
ways and then some situations trigger an emotion. I think we could train machines to detect those
situations and predict that the particular emotion will likely be felt if a human was playing one
of the characters. You have shown excitement and done a lot of excellent work with unsupervised
learning but there's been a lot of success on the supervised learning. One of the things I'm
really passionate about is how humans and robots work together and in the context of supervised
learning that means the process of annotation. Do you think about the problem of annotation of
put in a more interesting way is humans teaching machines? Yes, I think it's an important subject.
Reducing it to annotation may be useful for somebody building a system tomorrow but
longer term the process of teaching I think is something that deserves a lot more attention
from the machine learning community so there are people of coin the term machine teaching.
So what are good strategies for teaching a learning agent and can we design, train a system
that is going to be a good teacher? So in my group we have a project called a BBI or BBI game
where there is a game or a scenario where there's a learning agent and a teaching agent
presumably the teaching agent would eventually be a human but we're not there yet and the
role of the teacher is to use its knowledge of the environment which it can acquire using
whatever way brute force to help the learner learn as quickly as possible. So the learner
is going to try to learn by itself maybe using some exploration and whatever
but the teacher can choose, can have an influence on the interaction with the learner
so as to guide the learner maybe teach it the things that the learner has most trouble with
or just add the boundary between what it knows and doesn't know and so on. So there's a tradition
of these kind of ideas from other fields and like tutorial systems for example and AI
and of course people in the humanities have been thinking about these questions but I think
it's time that machine learning people look at this because in the future we'll have more and more
human machine interaction with the human in the loop and I think understanding how to make this
work better. Oh the problems around that are very interesting and not sufficiently addressed.
You've done a lot of work with language too, what aspect of the traditionally formulated
touring test, a test of natural language understanding in generation in your eyes is the
most difficult of conversation, what in your eyes is the hardest part of conversation to solve for
machines. So I would say it's everything having to do with the non linguistic knowledge which
implicitly you need in order to make sense of sentences. Things like the winner grad schemas
so these sentences that are semantically ambiguous. In other words you need to understand enough about
the world in order to really interpret properly those sentences. I think these are interesting
challenges for machine learning because they point in the direction of building systems that
both understand how the world works and there's causal relationships in the world and associate
that knowledge with how to express it in language either for reading or writing.
You speak French? Yes, it's my mother tongue. It's one of the romance languages. Do you think
passing the touring test and all the underlying challenges we just mentioned depend on language?
Do you think it might be easier in French than it is in English or is independent of language?
I think it's independent of language. I would like to build systems that can use the same
principles, the same learning mechanisms to learn from human agents, whatever their language.
Well, certainly us humans can talk more beautifully and smoothly in poetry. So I'm Russian originally.
I know poetry in Russian is maybe easier to convey complex ideas than it is in English
but maybe I'm showing my bias and some people could say that about French. But of course the
goal ultimately is our human brain is able to utilize any kind of those languages to use them
as tools to convey meaning. Yeah, of course there are differences between languages and maybe some
are slightly better at some things but in the grand scheme of things where we're trying to understand
how the brain works and language and so on, I think these differences are minute.
So you've lived perhaps through an AI winter of sorts. Yes. How did you stay warm and continue
with your research? Stay warm with friends. With friends. Okay, so it's important to have friends
and what have you learned from the experience? Listen to your inner voice. Don't, you know, be
trying to just please the crowds and the fashion and if you have a strong intuition about something
that is not contradicted by actual evidence, go for it. I mean, it could be contradicted by people.
Not your own instinct of based on everything you've learned. So of course you have to adapt
your beliefs when your experiments contradict those beliefs but you have to stick to your
beliefs otherwise. It's what allowed me to go through those years. It's what allowed me to
persist in directions that, you know, took time, whatever other people think, took time to mature
and bring fruits. So history of AI is marked with these, of course it's marked with technical
breakthroughs but it's also marked with these seminal events that capture the imagination
of the community. Most recent, I would say AlphaGo beating the world champion human go player
was one of those moments. What do you think the next such moment might be? Okay, sir, first of all,
I think that these so called seminal events are overrated. As I said, science really moves by
small steps. Now what happens is you make one more small step and it's like the drop that,
you know, allows to, that fills the bucket and then you have drastic consequences because now
you're able to do something you were not able to do before or now say the cost of building some
device or solving a problem becomes cheaper than what existed and you have a new market that opens
up. So especially in the world of commerce and applications, the impact of a small scientific
progress could be huge but in the science itself, I think it's very, very gradual and
where are these steps being taken now? So there's unsupervised, right? So if I look at one trend
that I like in my community, for example, and at me line, my institute, what are the two hardest
topics? GANs and reinforcement learning, even though in Montreal in particular, like reinforcement
learning was something pretty much absent just two or three years ago. So it is really a big
interest from students and there's a big interest from people like me. So I would say this is
something where we're going to see more progress even though it hasn't yet provided much in terms of
actual industrial fallout. Like even though there's Alpha Gold, there's no, like Google is not making
money on this right now. But I think over the long term, this is really, really important for many
reasons. So in other words, I would say reinforcement learning maybe more generally agent learning
because it doesn't have to be with rewards. It could be in all kinds of ways that an agent
is learning about its environment. Now, reinforcement learning, you're excited about. Do you think
GANs could provide something? Yes. Some moment in it. Well, GANs or other
generative models, I believe, will be crucial ingredients in building agents that can understand
the world. A lot of the successes in reinforcement learning in the past has been with policy
gradient where you'll just learn a policy. You don't actually learn a model of the world. But
there are lots of issues with that. And we don't know how to do model based RL right now. But I
think this is where we have to go in order to build models that can generalize faster and better,
like to new distributions that capture, to some extent, at least the underlying causal
mechanisms in the world. Last question. What made you fall in love with artificial intelligence?
If you look back, what was the first moment in your life when you were fascinated by either
the human mind or the artificial mind? You know, when I was an adolescent, I was reading a lot.
And then I started reading science fiction. There you go. That's it. That's where I got hooked.
And then, you know, I had one of the first personal computers and I got hooked in programming.
And so it just, you know, start with fiction and then make it a reality. That's right.
Yosha, thank you so much for talking to me. My pleasure.