Abstract
Individuals with developmental prosopagnosia present lifelong deficits recognising facial identity, but their ability to process facial expression is unclear. Addressing this issue is key for understanding the core deficit in developmental prosopagnosia, and for advancing knowledge about the functional mechanisms and development of normal face processing. Here we compared facial identity and facial expression processing in a large, online study with 128 prosopagnosics and 128 sex/age-matched controls. We used three experimental tasks of sorting, simultaneous matching, and sequential matching to assess facial identity and facial expression processing within the same format. Pilot data ensure all tasks were sensitive for detecting subtle deficits, were equally difficult across identity and expression versions, and produced sizeable inversion effects characteristic of face processing. Our main findings are twofold. First, prosopagnosics performed worse with facial identity than with facial expression, and they showed reduced inversion effects for facial identity but normal inversion effects for facial expression. Second, prosopagnosics showed subtle deficits for facial expression, but these deficits can be accounted for by their scores on a measure of subthreshold autism trait. These results provide strong evidence for a dissociation between facial identity and facial expression processing in developmental prosopagnosia that is qualitative, not quantitative, in nature. They also suggest that the core deficit in developmental prosopagnosia is specific to facial identity rather than generic to all aspects of face processing. Finally, our findings imply that facial identity and facial expression processing rely on functionally separate mechanisms that dissociate in development.
Meeting abstract presented at VSS 2018