Abstract
Motivationally relevant stimuli might reach awareness earlier than objects without such relevance. We used a visual masking paradigm to compare consciousness thresholds for neutral faces, threatening dogs and cups. Here, the subjects were presented with two stimuli–an image from one of the three object categories and its spatially scrambled counterpart–both of which were followed, at a varying stimulus onset asynchrony (SOA), by a spatially overlapping pattern mask containing features of objects from all three categories. Subjects then identified the category and the location of the unscrambled image. We defined the consciousness threshold as the smallest SOA at which the category and location of the masked image was correctly identified at an above chance accuracy. We reasoned that, on the one hand, (a) awareness of potentially dangerous objects might be adaptive for planning evasive behaviors; on the other hand, (b) consciousness might be suppressed due to the negative valence of such stimuli. We predicted that, of the three object categories tested, 1) faces, which are socially significant and more frequently encountered, would have the lowest consciousness threshold; 2) based on alternative (a), threatening dogs should have a consciousness threshold equal to or higher than that for faces but lower than that for motivationally neutral cups; 3) based on alternative (b), threatening dogs should have the highest consciousness threshold. Our results show that (i) faces have a lower consciousness threshold than both cups and threatening dogs, and (ii) supporting alternative (b), threatening dogs have a higher consciousness threshold than both faces and cups. Therefore, the minimal SOA for attaining awareness of stimuli might depend on their social and motivational relevance. Moreover, these results suggest that threatening information may be suppressed from awareness and therefore attain consciousness only when it becomes more visible at longer target-mask SOAs.