Subjects were taught to use one digit to press a button and reap a food reward. The subjects learned this behavior sequence and related it to a pleasurable outcome. The part of the brain stimulated in this response was also studied. It was found that through habitual stimulation, this part of the brain developed deeper pathways or patterns of brain responses. Thus in the absence of a food reward, the subjects tended to use that same finger to press the button, having associated it with a pleasurable event.
Human beings behave in much the same way when it comes to association.
We develop brain response patterns that dictate much of our behavior. This is exemplified by the phantom pains of amputees or when a particularly tall person unconsciously ducks even when there is a high enough doorway to enter without doing so. Over many years and many generations, neural pathways can be forged that are particularly difficult to overcome. To further illustrate this point, let us consider the long-time prisoner. Statistics show that after two or more years in prison, it is less likely that an inmate will be rehabilitated and become a productive member of society.