Measles, magic and misidentifications: a defence of the two-factor theory of delusions.

Corlett (Corlett, P. (this issue). Factor one, familiarity and frontal cortex: A challenge to the two-factor theory of delusions. Cognitive Neuropsychiatry) provides a robust critique of the two-factor theory of delusions. The heart of his critique is two challenges he derives from a paper by Tranel and Damasio (Tranel, D., & Damasio, H. (1994). Neuroanatomical correlates of electrodermal skin conductance responses. Psychophysiology, 31(5), 427-438), who illuminate the autonomic responses and brain damage of four patients often cited in support of the two-factor theory of Capgras delusion. I defend the two-factor theory against Corlett's two key challenges, arguing that his first challenge has been previously addressed, and that his second challenge is overstated. In my view, these challenges do not negate the two-factor account. Nevertheless, two-factor theorists - and computational psychiatrists - should continue to devise and test falsifiable predictions of their respective theories.