Jun 10 2009
The Pushmi-Pullyu of Brain Chemicals
Does an increase in testosterone levels cause behavior x? Or does behavior x cause an increase in testosterone? Or, even more confoundingly, is the answer both?
The relationship between behavior and brain chemicals is a complex one. Why? Our biology will certainly influence our behavior. But behavior can influence our biology as well. For example, perform this experiment: crack a big smile right now. Did you feel anything? I bet you did. The behavior of smiling caused changes in your brain chemistry. And it likely felt good. The reverse is true. Alter your brain chemistry in a similar fashion and you are more likely to smile.
In a recent study researchers found a link between the hormone progesterone and “interpersonal closeness.” In their experiment, female subjects in pairs proof-read a botany manuscript together or played a cooperative computer game. The results -
The progesterone levels of women who had engaged in the emotionally neutral tasks tended to decline, while the progesterone levels of women who engaged in the task designed to elicit closeness either remained the same or increased.
So there we have behavior influencing a hormone level. In a follow-up phase, the researchers discovered a link likely pointing in the other direction.
“During the first phase of the study, we found no evidence of a relationship between progesterone and willingness to sacrifice,” Brown said. “But a week later, increased progesterone predicted an increased willingness to say you would risk your life to help your partner.”
A pushmi-pullyu, by the way, is a fictional creature from an old Dr. Dolittle book/movie. The creature had two front ends connected by a middle. And that may be an apt metaphor for the relationship between brain chemicals and behavior. It seems to be a bi-directional beast.
