Hemispheric Asymmetry in Nonconscious Processing

Abstract

Here we investigated whether hemispheric asymmetry effects can be observed in nonconscious processing with a basic-level animal categorization (cat/dog) task. We found a significant nonconscious congruency priming effect when the prime was presented in the right visual field/left hemisphere but not when it was presented in the left visual field/right hemisphere when the prime duration was only 10 ms; the left-lateralized congruency priming effect was consistent with the left hemisphere superiority in processing abstract category information reported in the literature (e.g., Marsolek, 1999). This result thus showed that nonconscious processing can go beyond the sensory level to influence hemispheric asymmetry in the processing of category information. In contrast, this hemispheric difference was not observed when the prime was presented for 50 ms (nonconscious) or 150 ms (conscious). This effect may be because 10 ms subliminal information was insufficient to allow inter-hemispheric transfer/processing, allowing the hemispheric difference to emerge. It also suggests that hemispheric asymmetry may be better observed at subliminal level.