Matt Donnelly, "The science of free will " (2005)

Throughout the history of science, attempts have been made to answer the question of free will using scientific principles. Early scientific thought often pictured the universe as deterministic, and some thinkers believed that it was simply a matter of gathering sufficient information to be able to predict future events with perfect accuracy.

While not mechanistic in the same sense as classical physics, most current scientific theories are also deterministic, by necessity — it is a basic assumption of all scientific endeavors that the future can be predicted. It is also difficult, if not impossible, to write the mathematics for a non-predictive science.

On its face, quantum mechanics only predicts observations in terms of probabilities. Some interpretations of quantum mechanics may suggest that the universe, when viewed as a single system, is nonetheless deterministic, as there is no outside entity capable of making observations.

It is far from clear, however, that microscale interpretations of quantum mechanics can be applied to large systems in this way, and whether quantum mechanics ultimately describes a universe governed by laws of cause and effect or by chance is hotly debated — both by physicists and philosophers of science. Other interpretations are non-deterministic and many physicists find attempts to "interpret" quantum mechanics to be pointless

The leading contemporary philosopher that has capitalized on the success of quantum mechanics and chaos theory in order to defend incompatibilist freedom is Robert Kane, in The Significance of Free Will and several other writings.

Neurology and biology

Like physicists, biologists have also frequently addressed the question of free will. One of the most heated debates of biology is that of "nature versus nurture." How important are genetics and biology in human behavior compared to culture and environment? Genetic studies have identified many specific genetic factors that affect the personality of the individual, from obvious cases such as Down’s syndrome to more subtle effects such as a statistical predisposition towards schizophrenia.

However, it is not certain that environmental determination is less threatening to free will than genetic determination. The latest analysis of the human genome shows it to have only about 20,000 genes, the information content of which is but 2 or 3 megabytes, despite junk DNA, which may really have almost no information content. This implies that nurture may be more important than genetic determinists used to claim.

It has also become possible to study the living brain and researchers can now watch the decision-making "machinery" at work. A seminal experiment in this field was conducted by Benjamin Libet in the 1980s, wherein he asked subjects to choose a random moment to flick their wrist while he watched the associated activity in their brains. Libet found that the brain activity leading up to the subject flicking their wrist began approximately one-third of a second before the subject consciously decided to move, suggesting that the decision was actually first being made on a subconscious level and only afterward being translated into a "conscious decision", and that the subject's belief that it occurred randomly was only due to their perception.

A related experiment performed later by Dr. Alvaro Pascual-Leone involved asking subjects to choose at random which of their hands to move. He found that by stimulating different hemispheres of the brain using magnetic fields it was possible to strongly influence which hand the subject picked. Normally right-handed people would choose to move their right hand 60% of the time, for example, but when the right hemisphere was stimulated they would instead choose their left hand 80% of the time. Recall that the right hemisphere of the brain is responsible for the left side of the body, and the left hemisphere for the right. Despite the external influence on their decision-making, the subjects continued to report that they believed their choice of hand had been made freely.

Libet himself, however, does not interpret his experiment as evidence of the inefficacy of conscious free will — he points out that although the tendency to press a button may be building up for 500 milliseconds, the conscious will retains a right to veto that action in the last few milliseconds. A good comparison made is with a golfer, who may swing the club several times before striking the ball. In this view, the action simply gets, as it were, a rubber stamp of approval at the last millisecond. Also, for planning tomorrow's activities or those in an hour millisecond offsets are insignificant.

Neurology and psychiatry

There are several brain-related disorders that might be termed free will disorders: In obsessive-compulsive disorder a patient may feel an overwhelming urge, for instance, to wash his hands many times a day, and he will recognize the desire as his desire although out of control. In Tourette's and related syndromes, patients will involuntarily make movements, called tics, and utterances. In alien hand syndrome, also called Dr. Strangelove syndrome, after the Stanley Kubrick film, the patient's limb will make meaningful acts without the person’s determination.

Determinism and emergent behavior

In emergentist or generative philosophy of cognitive sciences and evolutionary psychology, free will is the generation of infinite behavior from the interaction of finite-deterministic set of rules and parameters. The unpredictability of the emerging behavior from deterministic processes leads to a perception of free will, though free will as an ontological entity does not exist.

As an illustration, strategy board-games like chess and Go, or Baduk, are rigorously deterministic in their rules and parameters, expressed in terms of the positions of the pieces or entities in relation to other entities on the board. Yet, chess and Go, with their strict rigor and rules, generate more moves and unpredictable behavior than any other games in existence. By analogy, emergentists or generativists suggest that the experience of free will emerges from the interaction of finite rules and deterministic parameters that generate infinite and unpredictable behavior.

Dynamical-evolutionary psychology, cellular automata and the generative sciences model emergent processes of social behavior on this philosophy — which seems to indicate that the perception of free will being untouched by causality is essentially a gift of ignorance or a product of incomplete information.