INTELLIGENCE AND VISUAL AND AUDITORY-DISCRIMINATION - EVIDENCE THAT THE RELATIONSHIP IS NOT DUE TO THE RATE AT WHICH SENSORY INFORMATION ISSAMPLED

Vickers (1995) proposed a measure of mental speed based on a discrimin ation of relative frequency. Like inspection time (IT), accuracy in Vi ckers' frequency accrual speed test (FAST) is assumed to be limited by the rate at which sensory input is discretely sampled. In both a visu al 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 w ith accuracy in both tasks. Contrary to a discrete sampling mechanism, however, accuracy was independent of stimulus duration, and there wer e reliable differences between trials. Although stronger for more high ly motivated subjects, the intelligence-performance relationship was n ot 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 fu rther sensory input.