- Inspection time
Inspection Time refers to the exposure duration required for a person to reliably
identify a simple stimulus. Typically a stimulus made up of two parallel lines differing in length and joined at the tops by a cross bar is presented (the so calledPi figure, after its similarity to the Greek π. The ability to quickly detect the identity of a stimulus is moderately [heritable| heritability] , and correlates withIQ .Overview
If asked which of the two lines in the figure below is longer; the left or the right, almost all non-visually impaired subjects can answer correctly 100% of the time. If, however, the stimulus is backward masked after a short period of time, the proportion of correct responses declines as the exposure duration reduces, and reliable individual differences emerge in the percent ideetified correctly at different intervals.
The task itself was proposed by
Doug Vickers [D. Vickers and P. L. Smith. (1986). The rationale for the inspection time index. "Personality and Individual Differences", 7, 609-623. ] as a measure the rate of accumulation of information.Ted Nettelbeck and others demonstrated it related quite strongly to psychometric intelligence [T. Nettelbeck and M. Lally. (1976). Inspection Time and Measured Intelligence. "British Journal of Psychology", 67, 17-22. ] , suggesting that differences inintelligence may reflect, in part, differences in the rate ofinformation processing - a theory proposed byArthur Jensen .One version of the inspection time stimuli is shown below (1) with the stimulus (short left given as an example), which is replaced by a mask (2). (3) indicates the opportunity for the subject to report which stimulus they saw at their leisure.
Genetics
Inspection time is moderately heritability [M. Luciano, D. Posthuma, M. J. Wright, E. J. de Geus, G. A. Smith, G. M. Geffen, D. I. Boomsma and N. G. Martin. (2005). Perceptual speed does not cause intelligence, and intelligence does not cause perceptual speed. "Biol Psychol", 70, 1-8. ] . This work from
Nick Martin 's group on the heritability of IT also demonstrated however that perceptual speed does not have a causal role inintelligence , but rather that IQ and IT are distinct reflections of some shared biological processes.References
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