The effect of attention on the speed of information processing

Covert spatial attention has been shown to improve performance on several perceptual tasks. Recent work (McElree and Carrasco, 1999Journal of Experimental Psychology: Human Perception and Performance251517 ^ 1539; Carrasco and McElree, 2001Proceedings of the National Academy of Sciences of the USA985363 ^ 5367) has demonstrated that, in addition to enhancing the signal, covert attention also speeds up the rate at which visual information is actually accrued. Using the response-signal speed ^ accuracy trade-off (SAT) procedure, we conducted two experiments to assess the effect of attention on the speed of information processing in an orientation-discrimination task. In addition to measuring accuracy and response time, we also simultaneously recorded event-related brain potentials (ERPs) to determine the locus of any attentional effect within the information-processing stream. For both experiments, accuracy of the orientation decision was higher for cued than uncued spatial locations. However, there were no significant differences between the cued and uncued conditions in the rate and intercept parameters of the SAT function. Also, a latency analysis of the lateralised readiness potential and of sensory ERPs revealed no cueing effects in premotoric and motoric processing times. Consistent with previous research, however, early ERP components were enlarged in amplitude at cued as compared to uncued locations. Altogether, whereas these latter ERP results indicate an effect of spatial attention on perceptual processing, we found no evidence for an acceleration of visual information processing with attention. It is conceivable, though, that covert attention speeds up the rate of visual information accrual in attentionally more demanding tasks.[Supported by an ESRC PhD studentship (R42200134069) to LB.]