Inspection time: An index for intelligence?

Recent publicity has been given to reports of high correlations between IQ and “inspection time”, a measure derived from simple discrimination which is assumed to provide an estimate of the time taken by a basic component of the decision process. However, this publicity has not recognised that the inclusion of mentally retarded participants in the experiments concerned may have led to inflated correlations, because of the marked extent to which the performance of retarded subjects is inferior to that of nonretarded subjects. Evidence from the performance of nonretarded subjects in three studies suggests that although speed of decision is related to IQ, the degree of association is smaller than recent publicity has suggested. Inspection time does not appear at present to hold promise as an index from which a “culture-fair” measure of intelligence might be derived.