Faces represent important information for social communication, because social information, such as face-color, expression, and gender, is obtained from faces. Therefore, individuals' tend to find faces unconsciously, even in objects. Why is face-likeness perceived in non-face objects? Previous event-related potential (ERP) studies showed that the P1 component (early visual processing), the N170 component (face detection), and the N250 component (personal detection) reflect the neural processing of faces. Inverted faces were reported to enhance the amplitude and delay the latency of P1 and N170. To investigate face-likeness processing in the brain, we explored the face-related components of the ERP through a face-like evaluation task using natural faces, cars, insects, and Arcimboldo paintings presented upright or inverted. We found a significant correlation between the inversion effect index and face-like scores in P1 in both hemispheres and in N170 in the right hemisphere. These results suggest that judgment of face-likeness occurs in a relatively early stage of face processing.

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The change of facial color and expression reflects our mental or physical condition. Previous behavioral studies indicated that there is a strong interaction between facial color and expression perception. This study investigated the contribution of facial color to expression recognition in blur images with the measurement of behavior and pupillary change. In the experiment, the face stimuli of facial colors (natural color, reddish) with different expressions (neutral, and anger) in 3 blur levels were presented. Participants performed a task of expression identification to the stimulus. Behavioral results indicated that the facial color has a significant contribution to expression recognition as blur level increases. Then, the results of pupillometry showed that the reddishcolor provided the information necessary to identify anger. These results showed the contribution of facial color increases in both psychophysics and pupillary experiment as blur level increases, which suggested that facial color emphasizes the characteristics of specific facial expression.

: Most people have experienced phenomenon where they perceive faces in the various non-face objects. This phenomenon is called "face pareidolia". In the present study, we investigated face pareidolia using pupillary response. The pupillary response was suggested to be influenced by high-level cognition. Therefore, we predicted that change of pupil diameter might be induced by face pareidolia. In our study, we measured that pupil diameter when stimuli were perceived as faces. The stimuli consisted of five circles including a big circle and four small circles. The subjects performed two tasks (face-like and symmetry) to the same stimuli in the block design. As results, pupil dilation in face-like condition showed differences between the face-like task and symmetry task. However, pupil dilation in symmetry condition showed no differences between tasks. These results suggest that this pupillary effect is specific for the face-like processing by top-down process and not specific for the symmetry processing.