Gaze dynamics toward familiar and unfamiliar faces in prosopagnosia.

Recognizing familiar faces is typically fast and automatic in neurotypical individuals but is markedly impaired in congenital prosopagnosia (CP) – a lifelong face recognition deficit without apparent brain injury. While previous research has focused on deficits in face perception or gaze to facial features in CP, it remains unclear whether individuals with CP can use facial familiarity, either explicitly or implicitly, to guide gaze dynamics in goal-directed tasks. Here, we investigated whether familiarity modulates gaze behavior in individuals with CP using two tasks previously validated in neurotypical populations: a face memorization task and a visual search task, each involving displays with both familiar (famous) and unfamiliar faces. The familiar faces in these tasks were categorized as either explicitly or implicitly visually recognized, based on participants’ ability to identify them by both image and name or only by name (respectively). Although individuals with CP performed worse than controls across both tasks (exhibiting lower accuracy and slower response times) they nonetheless showed preserved guidance of gaze by facial familiarity. When familiarity was explicit, their gaze patterns closely resembled those of neurotypical controls, with attention adjusted according to task demands: spending less time on familiar faces during memorization and more time on them during visual search. Notably, gaze differences also emerged for implicitly familiar faces, which, despite not being consciously recognized by image, elicited distinct viewing patterns compared to unfamiliar faces. These findings suggest that individuals with CP retain residual familiarity representation that can guide gaze even without explicit recognition. This provides novel evidence for preserved implicit processing in CP and advances our understanding of attention and memory mechanisms in face recognition.