A detailed investigation of facial expression processing in congenital prosopagnosia as compared to acquired prosopagnosia.

Whether the ability to recognize facial expression can be preserved in the absence of the recognition of facial identity remains controversial. The current study reports the results of a detailed investigation of facial expression recognition in three congenital prosopagnosic (CP) participants, in comparison with two patients with acquired prosopagnosia (AP) and a large group of 30 neurologically normal participants, including individually age- and gender-matched controls. Participants completed a fine-grained expression recognition paradigm requiring a six-alternative forced-choice response to continua of morphs of six different basic facial expressions (e.g. happiness and surprise). Accuracy, sensitivity and reaction times were measured. The performance of all three CP individuals was indistinguishable from that of controls, even for the most subtle expressions. In contrast, both individuals with AP displayed pronounced difficulties with the majority of expressions. The results from the CP participants attest to the dissociability of the processing of facial identity and of facial expression. Whether this remarkably good expression recognition is achieved through normal, or compensatory, mechanisms remains to be determined. Either way, this normal level of performance does not extend to include facial identity.