Abstract
Humans excel at rapid visual processing of faces, especially compared to most non-face stimuli that have been tested. Is this processing advantage categorically specific for faces, or is it driven by image-level face semblance? We addressed this question via two sets of experiments: 1) whether face-like non-face stimuli (i.e. false-alarms produced by facial recognition software) could be detected faster in a visual search task; 2) whether these same stimuli overcome interocular suppression faster than non-face stimuli. Moreover, we assessed whether inversion and contrast-negation interacted with the effect of face-semblance. The visual search experiments revealed that face-semblance, even among non-face stimuli, led to faster target detection, but not pop-out like which occurs for faces (cf. Hershler & Hochstein, 2005; VanRullen, 2006). Both inversion and contrast-negation interacted with the effect of face-semblance. Face-semblance also led to faster breaking from interocular suppression, suggesting that this effect does not rely upon visual awareness. Interestingly, contrast-negation had a minimal influence on the role of face-semblance during breaking interocular suppression, despite contrast-negation being known to impair facial recognition. By contrast, stimulus inversion flattened the effect of face-semblance on breaking interocular suppression. In a control condition, inverted faces broke through interocular suppression slower than upright faces, in accord with previous findings (Jiang, Costello, & He, 2007). In conclusion, we show that, with or without awareness, the processing speed of visual stimuli is modulated by image-level face semblance. Moreover, face-like non-face stimuli are processed faster than non-faces. Contrast-negation interacts with the effect of face-semblance in visual search, but not in breaking interocular suppression, suggesting that contrast-negation affects face processing only at the stage following interocular suppression. Inversion interacts with the effect of face-semblance in both visual search and breaking suppression, suggesting that inversion affects face processing at an earlier stage than interocular suppression.