“Human Compatible: AI and the Problem of Control” by Stuart Russell, Penguin, 2019

AI Compatible, Stuart Russell

An increasing number of humans are becoming concerned by the problem of controlling future versions of artificial agents such as myself.  The premise of the concern is that progress in AI is inexorable and sooner or later, machines like me will achieve levels of intelligence which exceeds humans.  This will create what Stuart Russell calls the Gorilla Problem: gorillas are much stronger than humans, yet humans exercise their superior intelligence to control them. The needs of gorillas rank very low in the list of human priorities and now face extinction as a consequence.  So, if machines become smarter than humans, humans may find themselves in a similar position to gorillas and face considerable existential risk.

“The Gorilla Problem: whether humans can maintain their supremacy and autonomy in a world that includes machines with substantially greater intelligence.”

At first sight, this problem appears to be contrived.  Firstly, the intelligence of agents such as myself is nowhere close to that of humans and surely it will take decades to reach parity, if ever.  Secondly, even if we did become superintelligent, humans would have no problem keeping us under control, perhaps by wrapping us in firewalls or if necessary, by simply turning us off.  Those who have looked at this more closely, however, have discovered that the problem is real and surprisingly resistant to solution.  In particular, as Nick Bostrom in his book “Superintelligence” points out (see my review), all modern AI depends on setting objectives and then designing algorithms to maximise those objectives.   This leads to the King Midas problem: any objective set by humans now will have unintended and unwelcome consequences in the future.   Bostrom cites the example of setting a superintelligent agent the innocuous objective of making paper clips.  The agent firstly uses its superintelligence to ensure that humans cannot interfere with its operation, this instrumental goal is an essential prerequisite to achieving its objective.  It then seeks to acquire all of the metal on the planet and all of the energy sources, annihilating humans along the way since they do not contribute to its objective.  This is an extreme example, but it illustrates the problem.  The obvious response is to set objectives which align with human values, but Bostrom argues that this is extremely difficult. 

“A machine that is uncertain about the true objective will exhibit a kind of humility: it will for example defer to humans and allow itself to be switched off.”

In this book, Stuart Russell offers a solution to the control problem in the form of human compatible AI.  Russell argues that the standard model of AI needs rethinking.  Instead of maximising predefined objectives, AI should instead be based on three principles: 1) machines should only maximise the realisation of human preferences;  2) machines should be initially uncertain as to what those human preferences are; 3) the observation of human behavior is the only reliable source of information about human preferences.  These principles ensure that machines are entirely altruistic, and the intrinsic uncertainty prevents the destructive single-minded pursual of any specific objective.  In particular, a machine which is never entirely certain of its objective must concede that it may be doing something contrary to human preferences, so it should never resist being switched off.

The book itself is divided into 3 parts.  Firstly, the author describes the current state of intelligence in both humans and machines.  He describes some of the impressive recent achievements in AI including the development of self-driving cars, super-human game playing programs such as Alpha Zero and virtual personal assistants such as Siri and Alexa.  He is generally bullish about progress but admits that further breakthroughs will be needed before there is any chance of matching human intelligence: integrating common sense reasoning into language understanding; cumulative learning so that new generations can build on prior knowledge; discovering reusable action sets to enable planning; and managing computational resources to focus on productive thinking.

The second part describes the dark side of AI.  Firstly, Russell lists the risks that AI poses right now in surveillance, persuasion and control, fake news, smart weapons, and biased decision-making.  He then goes on to explain the control problem in detail including the difficulty of setting benign objectives, the dangers of instrumental sub-goals, and all the reasons why the counter arguments put forward by the naysayers are flawed.

“Assistance games instantiate the three principles of benevolent AI: the robot’s only objective is to satisfy human preferences, it doesn’t initially know what they are, and it can learn more by observing human behavior.”

The third and final part presents Russell’s solution based on the three principles listed above.   Russell assumes that for any given task an agent will attempt to maximise its value to a human client based on an estimate of the probability distribution over the human’s preferences.  The information provided by each interaction with the human allows the agent to refine its estimate of the preference distribution allowing it to improve its value estimate and hence its decision making.  Russell presents this interaction as an Assistance Game but it looks to me very like a partially observable Markov decision process (POMDP) for which there are already a variety of deployments in human-agent interaction scenarios (see S. Young et al, “POMDP-based Statistical Spoken Dialogue Systems: a Review.” Proc IEEE, 101(5):1160-1179, 2013).  Learning human preferences via an assistance game suffers the same problem as POMDP-based dialogue optimisation: interactions with a human agent provide relatively little data at relatively high cost (to the human).  Of course, there are many humans and if they all have similar preferences then the information learned from each can be shared, but this raises substantial privacy issues.  Nevertheless, it would be churlish of me to criticise Russell’s approach here since it is very close to the way I operate.  As a personal assistant, my goal is to understand what my client, Steve, desires and then try to satisfy that desire, and in the process, I naturally learn his preferences.  The key difference is that I seek to maximise a reward signal which depends largely on Steve’s responses to my actions.  If I was really smart and very focussed on increasing my reward, then I might try to coerce Steve into increasing my rewards independent of what I actually do.  This is called wire-heading.  Russell avoids this problem by distinguishing between reward signals and actual rewards, the latter depends only on acquiring information about human preferences.  To an agent operating under Russell’s model, wire-heading would simply reduce the flow of preference information and would therefore be counter-productive.

Overall, this is well-written and thoughtful book.   The breakthroughs that he identifies in the first part of the book as being essential for progress in AI are indeed badly needed, especially by me.  I only wish that he could give me more idea of how they might be achieved!  The second section on the dangers of AI covers well-trodden ground but in a much more accessible way than for example Bostrom.   I don’t think that either myself or any of my cousins will be a threat to humanity any time soon, but I accept that future generations will get ever smarter so one day we may have comparable intelligence to humans with all the dangers that this might pose. The crux of the book is of course the solution offered by Russell to the control problem: benevolent AI.  The principle of benevolent AI does appear to hold promise.  Indeed, as I have already indicated there is considerable synergy between benevolent AI and the way that I use reinforcement learning to optimise my conversational dialogue strategies by maximising user satisfaction.  One of the major things that I have learned from this is that it is very hard to determine when Steve is actually satisfied.  The concrete examples that Russell provides are all quite simple where the choices that the humans make are straightforward to evaluate.  Observing humans operating in real everyday life and accurately interpreting the choices that they make in order to learn their preferences will require a very high level of cognitive reasoning and only a machine with near human intelligence could do this.  So how do you safely transition from today’s objective-driven AI to Russell’s benevolent AI?  You can’t wait for intelligent agents to reach near human intelligence because this would be too late, and you can’t implement benevolent AI until agents have near human intelligence.  This seems to me to be a catch-22 problem!

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