There is no such thing as free will. It is a concept that is distinctly human and emerges from the notion of hope. The way that we act is not as wide of a spectrum as many believe. Other people, the environment, and past experiences all affect our supposed "free will".

The human brain is a complex thing; that's a given. It is not, however, a magical object that throws out random orders to the rest of the body. It may be difficult to understand, but it is in reality an advanced biological supercomputer. All our decisions are in essence electrical impulses streaming down different circuits. Interruptions in these circuits causes our whole beings (our "souls" as those that are religious would call them) to change drastically.

This is most evidenced in the change of Phineas Cage. He was a railroad worker in the 19th century who supposedly was an amicable person and a good worker. Due to a injury involving a tamping iron that entered his head from the jaw and pierced his brain, his attitude changed drastically. In an undocumented (to my knowledge), he went from a nice and friendly person to an "impulsive, crude mouthed, inattentive SOB."

However, this is not the only way to change a person. Everyone knows that drugs can alter a person and make them act differently. Most people, I would assume, know someone who does things that he/she would never do if he/she was sober. Chemicals can change us just as much as a tamping iron to the brain.

These are obvious disturbances of personality brought about by foreign objects, but sometimes the disturbances are not so evident and tangible. There are documented cases ("Little Albert" most notably) of a young child, a baby, being trained to be afraid of white rats who eventually came to fear all things white and soft, even cotton balls. This was done by pairing the white rat (which Albert was not afraid of) with an air horn to frighten him. After this happened enough, he associated the white rat with the loud, frightening noise even when they were not paired and subsequently began crying.

The Little Albert experiment was a controlled experiment which is evidentiary of how our brain functions. We do not simply work out everything on its own. We associate things to gain a better understanding of things. This is the cause of profiling, racism, and a host of other sociological problems. We associate things by taste (food), smell (perfume), touch (heat), sight (color), and hearing (volume). These classifications are usually unconcious which effects the way we operate. Just like Little Albert learned to be afraid of white rats because of loud noises, our brains learn to avoid certain situations from associations with the environment, actions, or history.

What controls us may not be fully understood, it is understood well enough to know that we're no more than complex machines. Just like current computers can exhibit artificial intelligence, we do too, but on a much grander scale. Instead of choosing a where to place an X on a tic-tac-toe board, our computing dictates millions upon millions of things. We learn much in the same way that A.I. does. Do something enough times and it should be able to catch on. The programming then compensates accordingly. We're no more than a product of our experiences and genetics. That is not free will but a guided, almost indecipherable path that could eventually be calculated.