From Gene to Behavior, Traced

Tracing a behavior biologically means moving from gene to protein to circuit to hormone to environment and back, without skipping a level.

One trait — an anxious response to social evaluation — followed the whole distance: inherited variation in a transmitter system, its expression shaped by early environment, the amygdala and cortisol response it produces, the avoidance behavior that follows, and the way that behavior reshapes the environment that feeds back into expression. Ends by naming the two places in the chain where the evidence is strong and the one where it is not.