Abstract
Behavioural and neurological research suggests that emotional (relative to neutral) faces are more visually salient, with preferential access to awareness, for example in overcoming binocular rivalry suppression. However, it is difficult to determine to what extent such effects result simply from low-level characteristics as opposed to the emotional content of the face per se. Although spatial inversion has been used to control for low-level image characteristics, the extent to which inversion disrupts emotion processing is unclear. We applied both spatial inversion and luminance reversal to fear, happy, angry and neutral faces. These manipulations retained the contrast, mean luminance and spatial frequency profiles of the images but combining them made the emotion impossible to categorise. Observers viewed the normal and the manipulated images under continuous flash suppression: a single face was presented to one eye and high contrast dynamic noise to the other. Fear faces emerged from suppression (i.e. became visible) faster than the other three expressions. However, this pattern was equally apparent for the original and the manipulated faces. The properties that lead to the unconscious prioritisation of fearful faces are thus fully contained in unrecognisable images that share the same low-level visual characteristics. Our findings suggest that some emotion-specific effects may be driven entirely by low-level stimulus characteristics.
KG was funded by an ESRC studentship.