Last May, an article came out of DeepMind research titled Reward is enough. It was published in an artificial intelligence journal but PDFs of it are available free of charge.
The article points out that according to DeepMind researchers, using reinforcement learning and an appropriate reward signal is sufficient to attain AGI (artificial general intelligence). We have written about the perils and pitfalls of AGI before (see Existential event risks [-part-0], NVIDIA Triton GMI, a step to far[-part-1], The Myth of AGI [-part-2], and Towards a better AGI – part 3ish. (Sorry, I only started numbering them after part 3ish).
My last post on AGI inclined towards the belief that AGI was not possible without combining deduction, induction and abduction (probabilistic reasoning) together and that any such AGI was a distant dream at best.
Then I read the Reward is Enough article and it implied that they saw a realistic roadmap towards achieving AGI based solely on reward signals and Reinforcement Learning (wikipedia article on Reinforcement Learning ). To read the article was disheartening at best. After the article came out, I made it a hobby to understand everything I could about Reinforcement Learning to understand whether what they are talking is feasible or not.
Reinforcement learning, explained
Let’s just say that the text book, Reinforcement Learning, is not the easiest read I’ve seen. But I gave it a shot and although I’m no where near finished, (lost somewhere in chapter 4), I’ve come away with a better appreciation of reinforcement learning.
The premise of Reinforcement Learning, as I understand it, is to construct a program that performs a sequence of steps based on state or environment the program is working on, records that sequence and tags or values that sequence with a reward signal (i.e., +1 for good job, -1 for bad, etc.). Depending on whether the steps are finite, i.,e, always ends or infinite, never ends, the reward tagging could be cumulative (finite steps) or discounted (infinite steps).
The record of the program’s sequence of steps would include the state or the environment and the next step that was taken. Doing this until the program completes the task or if, infinite, whenever the discounted reward signal is minuscule enough to not matter anymore.
Once you have a log or record of the state, the step taken in that state and the reward for that step you have a policy used to take better steps. Over time, with sufficient state-step-reward sequences, one can build a policy that would work’s very well for the problem at hand.
Reinforcement learning, a chess playing example
Let’s say you want to create a chess playing program using reinforcement learning. If a sequence of moves ends the game, you can tag each move in that sequence with a reward (say +1 for wins, 0 for draws and -1 for losing), perhaps discounted by the number of moves it took to win. The “sequence of steps” would include the game board and the move chosen by the program for that board position.
championship games start from the initial board position.
If your policy incorporates enough winning chess move sequences and the program encounters one of these in a game and if move recorded won, select that move, if lost, select another valid move at random. If the program runs across a board position its never seen before, choose a valid move at random.
Do this enough times and you can build a winning white playing chess policy. Doing something similar for black playing program would build a winning black playing chess policy.
The researchers at DeepMind explain their AlphaZero program which plays chess, shogi, and Go in another research article, A general reinforcement learning algorithm that masters chess, shogi and Go through self-play.
Reinforcement learning and AGI
So now what does all that have to do with creating AGI. The premise of the paper is that by using rewards and reinforcement learning, one could program a policy for any domain that one encounters in the world.
For example, using the above chart, if we were to construct reinforcement learning programs that mimicked perception (object classification/detection) abilities, memory ((image/verbal/emotional/?) abilities, motor control abilities, etc. Each subsystem could be trained to solve the arena needed. And over time, if we built up enough of these subsystems one could somehow construct an AGI system of subsystems, that would match human levels of intelligence.
The paper’s main hypothesis is “(Reward is enough) Intelligence, and its associated abilities, can be understood as subserving the maximization of reward by an agent acting in its environment.”
Given where I am today, I agree with the hypothesis. But the crux of the problem is in the details. Yes, for a game of multiple players and where a reward signal of some type can be computed, a reinforcement learning program can be crafted that plays better than any human but this is only because one can create programs that can play that game, one can create programs that understand whether the game is won or lost and use all this to improve the game playing policy over time and game iterations.
Does rewards and reinforcement learning provide a roadmap to AGI
To use reinforcement learning to achieve AGI implies that
- One can identify all the arenas required for (human) intelligence
- One can compute a proper reward signal for each arena involved in (human) intelligence,
- One can programmatically compute appropriate steps to take to solve that arena’s activity,
- One can save a sequence of state-steps taken to solve that arena’s problem, and
- One can run sequences of steps enough times to produce a good policy for that arena.
There are a number of potential difficulties in the above. For instance, what’s the state the program operates in.
For a human, which has 500K(?) pressure, pain, cold, & heat sensors throughout the exterior and interior of the body, two eyes, ears, & nostrils, one tongue, two balance sensors, tired, anxious, hunger, sadness, happiness, and pleasure signals, and 600 muscles actuating the position of five fingers/hand, toes/foot, two eyes ears, feet, legs, hands, and arms, one head and torso. Such a “body state, becomes quite complex. Any state that records all this would be quite large. Ok it’s just data, just throw more storage at the problem – my kind of problem.
The compute power to create good policies for each subsystem would also be substantial and in the end determining the correct reward signal would be non-trivial for each and every subsystem. Yet, all it takes is money, time and effort and all this could be accomplished.
So, yes, given all the above creating an AGI, that matches human levels of intelligence, using reinforcement learning techniques and rewards is certainly possible. But given all the state information, action possibilities and reward signals inherent in a human interacting in the world today, any human level AGI, would seem unfeasible in the next year or so.
One item of interest, recent DeepMind researchers have create MuZero which learns how to play Go, Chess, Shogi and Atari games without any pre-programmed knowledge of the games (that is how to play the game, how to determine if the game is won or lost, etc.). It managed to come up with it’s own internal reward signal for each game and determined what the proper moves were for each game. This seemed to combine a deep learning neural network together with reinforcement learning techniques to craft a rewards signal and valid move policies.
Alternatives to full AGI
But who says you need AGI, for something that might be a useful to us. Let’s say you just want to construct an intelligent oracle that understood all human generated knowledge and science and could answer any question posed to it. With the only response capabilities being audio, video, images and text.
Even an intelligent oracle such as the above would need an extremely large state. Such a state would include all human and machine generated information at some point in time. And any reward signal needed to generate a good oracle policy would need to be very sophisticated, it would need to determine whether the oracle’s answer; was good or not. And of course the steps to take to answer a query are uncountable, 1st there’s understanding the query, next searching out and examining every piece of information in the state space for relevance, and finally using all that information to answer to the question.
I’m probably missing a few steps in the above, and it almost makes creating a human level AGI seem easier.
Perhaps the MuZero techniques might have an answer to some or all of the above.
~~~~
Yes, reinforcement learning is a valid roadmap to achieving AGI, but can it be done today – no. Tomorrow, perhaps.
Photo credit(s):
- From DeepMind research paper, A general reinforcement learning algorithm that masters chess, shogi and Go through self-play
- From DeepMind research paper, Reward is enough
