Are we what our molecules make us?

I've heard it since childhood: You either have chemistry with another person or not. PET imaging now is turning common sense into science.

Using PET, researchers at Ludwig Maximilians-University in Munich have validated a long-held theory that individual personality traits are determined by chemistry in the brain's endorphin system.

Specifically, they found that the binding to opiate receptors in the ventral striatum, an area of the brain known to be a central part of the reward system, correlates narrowly to people's degree of reward dependence. Subjects participating in the study who had a high need to feel rewarded by approval were also those with the highest uptake of opiates, or endorphins, as seen on the PET scans.

The finding may ultimately further our understanding of addictive behaviors and, in doing so, lead to better ways to treat substance abuse. Individuals suffering from a relative deficit of endorphins in their reward system, the researchers found, show increased reward dependence and, therefore, are probably more at risk for developing addictions. But there may be another lesson to be learned here, one with greater significance.

Taking a close look at the study, it is obvious that not every person short on endorphins turns to drugs, just as these same folks don't necessarily fall prey to an uncontrollable urge to seek approval. Speaking directly to that point, none of the 23 male subjects participating in the PET study had a history of substance abuse.

The researchers did not pay much attention to this fact, but I find it fascinating. The opiate needs of the subjects in this study were either satisfied in positive ways or left wanting, a distinction made through the application of will power. We are led to wonder what gave them the power to avoid drugs - and whether others with such chemical needs but less inner strength have no choice but to give in. The research does not include subjects who have fallen prey to illicit drug use or aberrant behavior. But future studies could.

Do principles of right and wrong taught to a child make the difference? What role does the fear of consequences play - the disapproval of others or more severe punishment, such as jail. These are broad and extraordinarily important questions for Western societies whose dedication to personal freedom carries the seeds of discord and chaos.

At no other time in history has it been possible to address philosophical issues with scientific tools. To make the most of it, we have to ask the right questions.