Individual differences in perceptual abilities predict target visibility during masking

Many studies have shown that the visual system can implicitly process a single stimulus under conditions of low visibility. However, it remains unknown whether this ability extends when viewing conditions become more difficult, and whether differences in early perceptual abilities modulate masking sensitivity. To address these issues, participants enumerated a variable number of target elements among distracters in two electroencephalography experiments. Either one (Experiment 1) or all targets (Experiment 2) were masked through object-substitution. Results showed that an event-related potential measure of selective individuation, the N2pc component, was modulated by target numerosity in both masked and unmasked trials, suggesting that multiple object individuation can operate in conditions of limited visibility. However, this effect was present mainly for participants with low masking effects, who overall showed more pronounced N2pc modulations as a function of target numerosity. Finally, oscillatory activity analyses revealed that early segmentation mechanisms, as reflected by lateralized gamma synchronization, were more active in participants with low sensitivity to masking, suggesting that individual variation in early perceptual functions is associated with susceptibility to masking such that more efficient segmentation and individuation mechanisms reduce the effects of masking. These findings cast doubt on the claim that effectively masked stimuli can be individuated.