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Abstract

Humans rely strongly on the shape of other peoples faces to recognize them. However, faces also change appearance between encounters, for example when people put on glasses or change their hair-do. This can affect face recognition in certain situations, e.g. when recognizing faces that we do not know very well or for congenital prosopagnosics. However, additional cues can be used to recognize faces: faces move as we speak, smile, or shift gaze, and this dynamic information can help to recognize other faces (Hill & Johnston, 2001). Here we tested if and to what extent such dynamic information can help congenital prosopagnosics to improve their face recognition. We tested 15 congenital prosopagnosics and 15 age- and gender matched controls with a test created by Raboy et al. (2010). Participants learned 18 target identities and then performed an old-new-judgment on the learned faces and 18 distractor faces. During the test phase, half the target faces exhibited everyday changes (e.g. modified hairdo, glasses added, etc.) while the other targets did not change. Crucially, half the faces were presented as short film sequences (dynamic stimuli) while the other half were presented as five random frames (static stimuli) during learning and test. Controls and prosopagnosics recognized identical better than changed targets. While controls recognized faces better in the dynamic than in the static condition, prosopagnosics performance was not better for dynamic compared to static stimuli. This difference between groups was significant. The absence of a dynamic advantage in prosopagnosics suggests that dysfunctions in congenital prosopagnosia might not only be restricted to ventral face-processing regions, but might also involve lateral temporal regions where facial motion is known to be processed (e.g. Haxby et al., 2000).