Abstract
Previous studies have shown that both low-level and high-level properties contribute to the strength of a stimulus in interocular competition. Indeed, stimuli of greater perceptual strength (e.g., high contrast) emerge from suppression faster than stimuli of weaker perceptual strength (e.g., low contrast). Recent studies have shown that stimuli of greater familiarity or recognizability also have a competitive advantage when processed under suppression. For example, upright faces emerge from suppression faster than inverted faces. It was also suggested that high and low spatial frequency components in face images selectively contribute to identity (FFA) and emotional expression (amygdala, Pulvinar, Superior Colliculus) analysis, respectively (Vuilleumier, et al. 2003). It is unclear however, whether it is the high-frequency-identity-analysis system or the low-frequency-expression analysis system that is behind the competitive advantage for upright compared to inverted faces. Thus in the current study, we tested whether the upright face advantage in interocular competition is stronger for the low or high spatial frequency component. Subjects were presented in one eye with upright and inverted face images that were either low- or high-pass filtered, while high contrast dynamic Mondrian noise patterns were presented to the other eye. Due to interocular suppression, subjects initially perceived only the dynamic noise. Subjects were asked to respond by button press as soon as an image was detected emerging from the noise pattern. Similar to what we have found before, results showed that it took less time for the upright faces to emerge from suppression than the inverted faces, but only in the low-pass filtered face image condition. This pattern of results suggests that it is the low-frequency-face-expression analysis system that is responsible for the upright face processing advantage under suppression.
This research was supported by the James S. McDonnell foundation, the US National Institutes of Health Grant R01 EY015261-01.