Skip to main content

Verified by Psychology Today

Free Will

Sapolsky on Free Will

Primates don't have it.

J. Krueger
Source: J. Krueger

[Free will is the] “internal forces I do not understand.” ~ Marvin Minsky, quoted in Behave by Robert M. Sapolsky

Robert Sapolsky, biologist, primatologist, and endocrinologist, has transcended his fields of origin and written a magisterial work on human nature (Penguin, 2017). He draws on anthropology, psychology, neuroscience, and behavioral economics as they relate to his central question: Can we understand and perhaps even predict why and when people behave shabbily or decently? And can we do this without resorting to moral philosophy or folk psychology? His answer, evolving over 700 pages, is that yes we can, but it is complicated and will remain so. Everything he offers by way of answering his question is grounded in a traditional and sturdy scientific worldview as conceived during the enlightenment and having evolved since. Sapolsky rejects mysticism and convenient shortcuts. He accepts uncertainty as a feature of the scientific life. At one point, he notes that it may well be that 51 percent of scientists hold one view on a critical issue, whereas 49 percent hold a different view. But such a statistical breakdown does not entail or legitimate a breakdown of rationality. There is truth to be discovered, though it may take a while.

Sapolsky sees humans as biological beings with culture. Biology and culture are deeply intertwined. To see them as opposites is pointless. The conjunctions and intersections of biology and culture can be studied rigorously. Every step of the way, biological and nonbiological (experience, culture) factors shape what humans do. This is a staunchly materialistic and deterministic outlook. Interestingly, Sapolsky does not emphasize the term causation, perhaps because he fears it might be misunderstood as “main-effect causation.” Instead, he sees the myriad of influencing factors as modulating one another. In time, the reader learns that Sapolsky has no use for the notion of free will. To be crystal-clear, Sapolsky nonetheless dedicates his penultimate chapter to the issue, spelling out like only a hard-shell scientist can that any version of the free-will argument reduces to the homunculus hypothesis, the illogicality of which is easily shown when it fails the infinite regress test.

As a biologist, Sapolsky believes that all experience and behavior, as well our unconscious doings, are features of biological (wet) activity of the brain (which culture and experience can mold and modulate). When we discuss thoughts, we talk at a different level of abstraction than when we discuss, say, the activity of the default mode network, but take the brain away, and the thoughts are gone. In contrast, the free will hypothesis requires input that is not of the biological kind, in other words, it asserts that thoughts can arise independently, or ‘freely’ as it were. This presumed independence has a crucial implication. It means that the free-will hypothesis asserts knowledge of something (‘We know that free will exists and that it can affect behavior’) that must be, by the very definition of free will, unknowable. If we explained, understood, and predicted free will, it would no longer be free. In other words, the very attempt to harness the idea of free will in scientific terms is self-refuting.

What’s left for those who are not bothered by this conceptual collapse is the metaphorical homunculus, the little person inside the person who acts as a pilot within the brain but who is not of the brain. He makes free decisions, unconstrained by what the brain is doing. But what is the psychology and the biology of this homunculus? Must we not postulate a mini-homunculus inside of this homunculus, and so on and so forth? We’d get infinite regress and that explains nothing.

Sapolsky’s substantive contribution is to review multiple layers of naturalistic sources of behavior and experience. From genes, to neurons, to hormones, to local culture and norms, there are plenty of non-metaphysical contributions to any particular decision or choice the organism makes. Sapolsky knows, however, that the explained variance does not come close to 100 percent. Things are too complex; we simply don’t know enough, and we probably never will. The game of science is a subtraction game (mind Minsky). Each demonstrated causative or modulatory effect we can attribute to forces in the environment, the past, or the insides of the biological organism reduces the space for the homunculus to exercise its putative free will. Sapolsky presents many illustrations of the progress of the subtraction game over historical time. My favorite is the trial of the pig. In 1457, a grown pig was tried and convicted for eating a child, and subsequently executed. The piglets, however, were spared, being “found too young to have been responsible for their acts” (p. 585). All pigs are nowadays off this particular hook, and so are young humans. We don’t try pigs anymore - although we might get mad at Sparky for urinating on the rug - but we still consider healthy and mature humans appropriate homes for homunculi. In theory, the subtraction game of science will eventually relieve us all of the witch hunt of personal responsibility, but even Sapolsky doubts that this will happen in our lifetime.

So what is the proper domain of the free-will-munculus today? Sapolsky reviews several answers free-willers have proposed. One proposed niche of free will is “around the edges of biology” (p. 588), where no strong desires assert their biological nature. Naturally, Sapolsky asks whether being able to decide freely which socks to wear is the kind of free will that’s worth fussing about. Another proposed niche is “decisions that are slow and deliberative” (p. 592). This is interesting because Sapolsky himself seems to be an adherent of the two-systems framework of cognition, where system 1 is swift and intuitive and system 2 is slow, reflective, and working with great effort. Yet, the latter does not spell freedom. Hard cognitive work is as much a biological brain activity as is quick intuition or emotion. Sapolsky’s book is full of examples of how the frontal cortex does its biological job. Next, Sapolsky disabuses us of the folk distinction between compulsion and "regular" causation. Both are studyable in biological and neuroscientific terms, and both are lawful instead of ‘free.’ Then, he briefly reviews the famous Libet experiments, which showed that the brain gets ready to do X (lift a finger) before the person realizes that it does. A strike against free will. Libet himself thought that perhaps we have some freedom to abort an action already prepared. If so, that would be a weird homunculus who can only choose to not act (see next point about resisting temptation).

After reviewing these versions of the ‘mitigated’ free will argument, Sapolsky arrives at the one that he considers most powerful and most destructive, that is, the idea that free will is there to make you work harder, act morally, and resist temptation. Doing so, he has to, somewhat inconveniently, critique the work of his Stanford colleague Carol Dweck. Dweck showed that in the United States, kids who were praised for successful work with reference to their talent will work less hard in the following, whereas kids who are praised for their effort will work harder. And isn’t that great? To Sapolsky, these responses “fall on either side of one of one of the deepest lines drawn by believers in mitigated free will. It is the belief that one assigns aptitude and impulse to biology and effort and resisting impulse to free will” (p. 596). This divide boils down to the Calvinist work ethic and Sapolsky will have none of it. Effort and resisting temptation are products of a wealth of natural factors: blood glucose levels, the socioeconomic status of the family, a concussive head injury (or absence thereof), sleep quality, prenatal environment, among many more.

With the demise of the free-will hypothesis comes a final question: What with punishment in the name of justice, and our desire to mete it out? The belief in free will is in part rooted in this desire, and often people ask without blushing ‘What if we denied free will – even if it truly does not exist – would we not run wild, raping, pillaging and burning’ (Clark, Luguri, Ditto, Knobe, Shariff, & Baumeister, 2014). In other words, is it not the fear of punishment on the free will assumption that keeps us in society’s line? Sapolsky has no patience for this view, and it is refuted all too easily. Of course society can create negative consequences for those who violate norms and other people’s rights. The goal is to protect or compensate victims, and to rehabilitate offenders if possible. No assumption of free will is necessary for this agenda. We do, after all, deliver consequences to shape the behavior of non-human animals. In rare occasions, it might even be necessary to kill a rogue elephant (Orwell, 1962) [1] to put an end to destruction. Yet, letting elephants know that we deny them free will, does not turn them rogue.


Clark, C. J., Luguri, J. B., Ditto, P. H., Knobe, J., Shariff, A. F., & Baumeister, R. F. (2014). Free to punish: A motivated account of free will belief. Journal of Personality and Social Psychology, 106, 501-513.

Orwell, G. (1962). Inside the whale. London, UK: Penguin. Essay first published in 1936.

Sapolsky, R. M. (2017). Behave: The biology of humans at our best and worst. New York: Penguin.

[1] Read Orwell's brilliant and wrenching essay and ask yourself if you think that he acted out of his free will.

More from Joachim I. Krueger Ph.D.
More from Psychology Today