Improved reaction time method, information processing speed, and intelligence

Two experiments are presented which were designed to enhance the sensitivity of RT as an information processing correlate of general ability. The first measured RT to a rapid game-like sequence of stimuli using 16 participants. Correlations with IQ in this task were negligible. The second experiment adapted the methodology of Jensen & Munro (1979). Stimuli were presented at a constant, reduced ISI to lower uncertainty about stimulus onset time and to decrease the session duration. Measurement of the decision time period was enhanced in two ways. The stimulus duration was shortened to 50 ms, thus fixing the onset of decision time to within 50 ms of stimulus onset. In addition, stimulus masking was used to restrict sampling of the stimulus to the period prior to movement onset. Finally, participants were reinforced verbally when they exceeded their own average performance to aid motivation. Using this method, data recorded from 30 participants showed a correlation of 0.56 between WAIS-R Full Scale IQ and rate of information processing as measured by the difference in the RTs recorded for two and four choice tasks (0.71 if corrected for restriction of range). These data are interpreted in terms of mental efficiency theories of intelligence.