Inspection Time and Intelligence: A Meta-Analysis

A meta-analysis of research on the relationship between inspection time (IT) and intelligence (IQ) was performed to: (1) determine whether a nonzero relationship between IT and IQ exists, (2) estimate the size of this relationship if it exists, and (3) test whether IT is ontogenetically related to g. Separate meta-analyses were initially conducted for results of studies using measures of general IQ, performance IQ, and verbal IQ for studies using samples of adults, children, and the mentally retarded. They were first conducted on the published (uncorrected) correlations. Following this, the resultant values were corrected for the extraneous effects of the artifacts (viz., sampling error, error of measurement, and range variation) and the meta-analyses were repeated. Results of these meta-analyses indicate that IT is related (negatively) to IQ, at least with measures of general IQ and performance IQ. For adults, with general measures of IQ, this correlation is about .54, after correction for the effects of artifactual sources of error ( . 30 prior to correction). IT, however, also appears to measure other factors besides g, possibly perceptual organization, which is reflected in the higher relationship of IT to performance measures of IQ. Finally, the theory that IT is ontogenetically related to IQ does not receive support. Rather, results of this study suggest that the degree of the IT-IQ relationship is relatively constant across age, at least through the range of ages tested in the literature.