genetics of learning

In its simplest sense, we imagine that learning occurs through a series of positive and negative rewards. Some actions lead to pleasure, others to pain, and it seems reasonable to expect that people will repeat the actions with pleasurable results and avoid those that ended in pain. Yet, we all know people who aren't deterred by the idea of punishment. We all know people who never seem to learn. Could there be a physical reason, hidden in their genes? In December 2007, Science published a study by Klein et. al. (1) where they asked if a specific genotype at a location called "DRD2-TAQ-IA"…