INTELLIGENCE AND THE EFFECTS OF PERCEPTUAL PROCESSING DEMANDS, TASK-DIFFICULTY AND PROCESSING SPEED ON P300, REACTION-TIME AND MOVEMENT TIME

Event-related potentials (ERPs) were recorded to the memory set and pr obe stimuli in a Sternberg memory-scanning task and compared to intell igence scores on the Multidimensional Aptitude Battery (MAB). The memo ry set was changed on each trial and all items in the memory set were presented simultaneously. Only the probe stimulus required a decision and response. P300 amplitude to the memory set increased as the memory set size increased; this is thought to be a result of the effects of demands for processing resources. A pattern of weak negative correlati ons were observed between P300 amplitude to the memory set and MAB sco res. In contrast, P300 amplitude to the probe stimulus decreased with increases in memory set load and there was a pattern of weak positive correlations with MAB scores. It is suggested that P300 amplitude to t he memory set is affected by task difficulty. The latency of the P300 component of the ERP was used as an indicator of the relative speed of information processing. This allows the assessment of processing spee d without requiring a physical response. Higher-ability participants d isplayed longer P300 latency to the memory set stimulus than lower-abi lity participants while there was no discernable effect on P300 latenc y to the probe stimulus. This contradicts a pure speed of processing e xplanation of the relation between P300 latency and intelligence. The longer P300 latency to the memory set suggests that higher-ability par ticipants devoted more time to stimulus analysis and planning than-low er ability participants.