Deficient empathy is related to amygdala dysfunction.3 The amygdala plays a central role in aversive conditioning. Through this form of reinforcement learning, persons learn to respond with fear to a previously neutral action or object, after the action or object has been paired with the occurrence of an aversive event.28 Indeed, amygdala responses during prototypical forms of reinforcement learning are reduced in persons with psychopathic traits.29 Functional magnetic resonance imaging (fMRI) studies have shown that adolescents with callous–unemotional traits, as compared with adolescents without such traits, have reduced amygdala responses to images of faces with fearful expressions30–32; these weaker responses are presumably due to deficient empathy. Such studies require participants to view a series of faces that vary in their emotional features; faces with fearful expressions preferentially engage the amygdala relative to other expressions (Fig. 2).
