Sunday, June 19, 2011

The Illusion of Free Will

We like to think that every decision we make is made out of free will. While the concept of free will seems to make some sense at an intuitive level, it seems rather slippery when trying to define it. What entity other than our brain is making the decision, and on what grounds, based on what input? And what are the laws that determine how that entity is making a decision?

It seems rather dreadful that decisions are made according to "an algorithm". In particular, a *deterministic* algorithm is rather unappealing because it implies that our genetic make-up, in combination with everything we have experienced
in our lifetime plus the environmental factors that are in play right now are input to a function that deterministically outputs a decision:
It seems to imply that we cannot be held responsible for our actions: they are simply a deterministic function of our history and the decision was predetermined anyway. We have no free will to change that outcome.

Despite its unattractive philosophical implications, I think this is exactly what is going on. We have no issue accepting this point of view for plants, in which case the FUNCTION is rather simple. Even lower animals such as fish or even crocodiles seem highly predictable in their responses to the environment. In the case of humans this is definitely not true. Our responses are (fortunately) partly predictable
but also partly unpredictable. There may be a good reason for a certain amount of unpredictability in nature. Imagine a cheetah chasing a gazelle. If the swerving movements of the gazelle were predictable for the cheetah then the cheetah could anticipate them and easily catch the gazelle. It is therefore likely that the gazelle has developed an algorithm that is very hard to predict for the cheetah, i.e. a seemingly random strategy to swerve left or right. Also apes living in large social communities were probably prone to similar evolutionary pressures: predictable responses can lead to exploitation and manipulation by others and thus have negative fitness value.

Seemingly random behavior does not mean this behavior is not deterministic. The decision process can become so complex that the tiniest changes in the environment can cause a completely different decision. This sensitivity or instability is the definition of "chaos" and according to some, unpredictability should be the correct definition of randomness, irrespective of whether something is deterministic or not. It is not even quite clear what true randomness means to be honest. Perhaps quantum mechanics is the only theory that claims randomness at a fundamental level (e.g. not caused by chaos), but even here the jury is still out. Even if our behavior is partly random, then what does that solve in terms of free will? A decision does not become more free if it is random.

To me the only logical conclusion is that our behavior is deterministic albeit in a very complex and unpredictable way. There is some interesting evidence for such a
theory. Experiments show that decisions are made in the brain even before we become aware of them. This means that at the very least a significant fraction of our decisions we make are made completely unconsciously and our body only fools ourselves into thinking that we made this decision consciously.

Predicting human behavior (decision making) may turn out to be impossible even with the fastest supercomputers. This feels like good news, because it would be
very unsettling to have a clone build after you that can perfectly predict what you will do 1 second from now. But ultimately we may have to accept that we can build
robots that can display equally complex behavior that are in no way inferior to us.

Finally a word on the legal implications of a theory of this kind. Does this mean we cannot send anyone to prison anymore because s/he committed a murder?
Of course not! Whether actions are predetermined or not has nothing to to do with this. The reason we send people to prison is because we don't want this person to
do it again and to scare other from doing it. These functions of punishment remain perfectly valid. We should never punish out of revenge or retribution. It is useless and serves no function to society.


  1. Dear Professor Welling,

    Having read your post, I remembered a quote (I don't remember who exactly said this, but for some reason Einstein's essay "The world as I see it" comes to mind): "A man can do as he wills but not will as he wills". As soon as one begins questioning such fundamental (and intuitive) notions, one inevitably runs into a deeper problem: introspection. Can a doubtful mind undoubtedly answer questions about the doubtful self?

    Perhaps free will is free will (in whatever intuitive sense) as long as we do not question or examine it. To draw a parallel with quantum mechanics, as you mentioned it: the position and momentum of a particle are completely (simultaneously) determined until we begin measuring them, thus perturbing the system.

  2. Can brain be modeled as a machine that takes the input and calculates the output?

    Here the output is the will or the decision.
    and inputs are 1) Surroundings or current circumstance. 2) Past experience. 3) The mapping method (or the mapping model) one uses to map circumstance to past experience.

  3. Hi Max, I totally agree with you on this one. My view of free will has always been that from a theoretical level, it doesn't exist (as I believe we are fully determined by the laws of physics), on the other hand, at a *practical level*, free will *does* appear to exist because we can't fully predict (in practice) people's behavior, so they do *look like* they have free will... So the 'free will' concept is still a useful approximation to the fact that we cannot predict fully other's behavior, due to chaos, fundamental computational intractability, etc.

    In any case, I also agree that the only constructive reason to punish someone is for protection or deterrence...

  4. The function of Decision can be re-modeled as
    This, is because people only remember their experiences and based on that they select their course of action.
    Thus, a person who is acquitted of his crime, can commit the crime again (if he feels he can easily cheat the system) or cannot (if he feels he should have been convicted but somehow luckily escaped).
    This learning from experience can be mapped to reinforcement learning.
    Someday it might be possible to make human-like decisions. Lets hope that day is soon.

  5. Thanks for posting this info. I just want to let you know that I just check out your site and I find it very interesting and informative. I can't wait to read lots of your posts.