Intelligence and visual and auditory discrimination: Evidence that the relationship is due to the quality of the stimulus representation rather than to the rate at which sensory information is sampled

Abstract

Proposed a measure of mental speed based on a discrimination of relative frequency. Like inspection time (IT), accuracy in Vickers' frequency accrual speed test (FAST) is assumed to be limited by the rate at which sensory input is discretely sampled. In both a visual and an auditory experiment, the duration of stimuli varied between 30 ms and 70 ms over successive trials. In line with previous results, accuracy in both versions was stable and reliable, as was performance on individual trials. Psychometric intelligence was also correlated with accuracy in both tasks. Contrary to a discrete sampling mechanism, however, accuracy was independent of stimulus duration, and there were reliable differences between trials. Although stronger for more highly motivated subjects, the intelligence-performance relationship was not attributable to motivational differences. The results are discussed in terms of a capacity-limited memory model and an attenuation model, in which the stimulus representation is degraded by the arrival of further sensory input.