 In another version of the two-factor theory (McKay 2012), the young woman adopts the impostor hypothesis because she suffers from a neuropsychological impairment responsible for the unusual event (factor 1) resulting in the anomalous experience. But the unusual event is not the only factor responsible for the formation of the delusion. The young woman also has a bias towards explanatory adequacy (factor 2) which leads her to accept a hypothesis that matches her unusual experience even when such hypothesis has a low prior probability and conflicts with some of her existing beliefs. The Capgras delusion is adopted because the delusional hypothesis explains (‘fits’) the data, that is, the absence of a feeling of familiarity towards a face that should be well-known.