Normal greeble learning in a severe case of developmental prosopagnosia.

A central question in cognitive neuroscience is whether mechanisms exist that are specialized for particular domains. One of the most commonly cited examples of a domain-specific competence is the human ability to recognize upright faces. However, according to a widely discussed alternative hypothesis, face recognition is instead performed by mechanisms specialized for processing any object class for which an individual has expertise. Faces, according to this domain-general hypothesis, are just one example of an expert class. Nonface object expertise has been intensively investigated using a training procedure involving an artificial stimulus class known as greebles. A key prediction of this hypothesis is that individuals with face recognition impairments will also have impairments with other categories that control subjects have expertise with. Our results show that a man with severe prosopagnosia performed normally throughout the standard greeble training procedure. These findings indicate that face recognition and greeble recognition rely on separate mechanisms.