Abstract
Several studies have shown that the meaning of stimuli under continuous flash suppression (CFS) is processed unconsciously (e.g., Costello et al., 2009). However, Kang et al. (2011) found the opposite result. To reconcile conflicting evidence, we hypothesized that inattention to the suppressed stimulus under CFS makes its semantic information available. Although counter-intuitive, this hypothesis is reasonable because of the following two reasons. Attention is not necessary for semantic processing (Luck et al., 1996), while rivalry suppression is attenuated without attention (Brascamp & Blake, 2012). Taken together, attention withdrawn from rival figures makes interocular suppression weak so that semantic information under CFS becomes available. We tested this hypothesis by obtaining the N400 component, a sensitive ERP measure for semantic processing, while participants were performing a semantic judgment task under CFS. To manipulate deployment of spatial attention, we adopted a cueing paradigm and resulted in three conditions. In the valid condition, the target was presented in a cued location of the suppressed eye. In the invalid condition, the target was presented in the opposite-to-the-cued location of the suppressed eye. Finally, in the visible condition, the target was presented to both eyes to ensure the cue validity, because participants had to make semantic judgments of the invisible targets in most of the trials. Consistent with the hypothesis, N400 modulation was absent in the valid condition but present in the invalid condition with the chance level semantic judgment performance. More importantly, the N400 amplitude obtained from the invalid condition was negatively correlated with independently obtained participants’ detection performance, indicating how much feature information was consciously available. This result suggests that attention drawn to the target location disrupted unconscious semantic processing even in the invalid condition. To summarize, the current study demonstrated that inattention to the target location makes semantic analysis possible during CFS.
Meeting abstract presented at VSS 2015