Yingshi Ding^1,2 (), Runnan Cao², Zhen Yuan³, Sheng He², Peng Zhang²; ¹Faculty of Education, University of Macau, Macau, China, ²State Key Lab of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China., ³Faculty of Health Sciences, University of Macau, Macau.

Face recognition is a holistic process that relies on the integration of facial features, normally a rapid process completed in a fraction of a second. A “double face” with two eyes and two mouths allows multiple possibilities of face integration. Observers often feel uncomfortable and disturbed when viewing double faces, possibly due to the continuation of face integration process. Therefore, the double face illusion may serve as a useful paradigm to study the face integration process. In an eye-tracking experiment (N = 21), subjects performed a two-back task based on the identity of face images, with normal faces and double faces presented in separate runs. Results show that subjects had fewer fixations in the eye region and more fixations in the mouth region when they viewed the double face images. In addition, there were more saccades in-between the eyes and mouth regions when subjects viewed the double face images. These results are consistent with continued attempts to integrate facial features into holistic face representations. In a fMRI experiment (N = 7), BOLD activity were measured during prolonged viewing of normal face and double face images. The double faces produced significantly stronger BOLD activations in the right FFA. More importantly, the generalized Psychophysiological Interactions analysis revealed significantly stronger functional connectivity between rFFA (used as a seed ROI) and right OFA in double face compared to normal face condition. Conclusion: These results suggest a recurring integration process in a “double face” illusion, which enhanced the activation in the fusiform face area and its functional connectivity with the occipital face area.