Perceptual biases for fearful facial expressions are observed across many studies. According to the low-level, visual-based account of these biases, fear expressions are advantaged in some way due to their image properties, such as low spatial frequency content. Breaking continuous flash suppression (b-CFS) has explored these effects, and demonstrated similar biases for detecting fearful facial expressions. However, there is a degree of empirical disagreement regarding the range of spatial frequency content. Recent findings from a b-CFS study highlight the role of high, rather than low spatial frequency content in determining faces’ visibility. The present study contributes to ongoing discussions regarding the efficacy of b-CFS, and shows that the visibility of facial expressions varies according to how faces are normalised for physical contrast and spatially filtered. Findings show limited evidence of a bias for detecting fearful facial expressions, but importantly, they show that such biases are less likely to occur when faces are normalised for apparent, perceived contrast, compared to physical contrast. Together these findings further the current understanding of the combined effects of spatial frequency and contrast on face visibility under b-CFS, and raise important questions regarding procedures used to standardise facial stimuli.
Suppression durations for facial expressions under breaking continuous flash suppression: effects of faces’ low-level image properties
