A psychological refractory period in access to visual short-term memory and the deployment of visual-spatial attention: multitasking processing deficits revealed by event-related potentials.

In this psychological refractory period (PRP) experiment, a tone (T1) was presented, followed by a visual target (T2) embedded in a bilateral display, and a speeded response was required for each target. The T1-T2 stimulus onset asynchrony (SOA) was 300, 650, or 1000 ms. Mean response time to T2 increased as SOA was reduced, replicating the well-known PRP effect. Importantly, the N2pc component of the event-related potential was progressively attenuated as SOA was reduced, and the onset latency of the sustained posterior contralateral negativity (SPCN) that follows the N2pc was progressively lengthened. Conditional analysis based on Task1 difficulty corroborated the analyses based on effects of SOA. The results suggest that central processing leading to the PRP effect interferes with the deployment of visual-spatial attention (as indexed by the N2pc) and delays encoding into visual short-term memory (as indexed by the SPCN onset latency).