Following an auditory warning tone and a delay, one of the lights is illuminated and the participant releases their finger from the home button.
However, participants can shift decision time into the movement phase by releasing the home button while the decision-making is still incomplete.
Variance or standard deviation in intra-individual RTs can be extracted to measure individual differences in response variability.
Simple reaction time correlates with general cognitive ability,[4] and there is some evidence that the slope of responding on the Jensen box does as well.
[2] Ian Deary and colleagues, in a population-based cohort study of 900 individuals, demonstrated correlations between IQ and simple choice RTs between –0.3 and –0.5.