Abstract :
This paper presents a rationale for a new measure of ‘mental speed’, based on a task in which subjects discriminate the relative frequency of flashes on one or the other of two lamps. In this ‘frequency accrual speed test’ (FAST), accuracy is interpreted as a measure of the rate at which flashes are registered. By assuming that sub-optimal performance is due to a random failure to register flashes, predictions are derived for a binomial and a hypergeometric version of the test. A procedure for estimating inspection time (IT) is given, and optimal values for the task parameters suggested. Results from eight studies are presented. These show that accuracy in the FAST procedure provides a stable, reliable, and robust measure, not obviously susceptible to different strategies or to practice. In four out of six studies, accuracy in this type of task showed a significant positive correlation with tests of intellectual performance, and in five out of five studies accuracy was negatively correlated with IT (significantly in two). These results show that accuracy in the FAST procedure may provide a useful measure of the speed with which sensory information is sampled. A programme for further testing is outlined.
