Inspection Time and Measured Intelligence

Abstract

Ten subjects with WAIS Full Scale IQ scores ranging from 119 to 47 were required to discriminate between two lines of markedly different length, exposed in random order for ten different durations, by pressing one of two keys. Estimates of inspection time gamma, the rate at which sensory input is accumulated and passed to subsequent decision processes, were calculated directly from the psychometric functions obtained gamma was found to correlate negatively with subtests contributing to Performance IQ. There was a substantial degree of consistency between estimates of gamma on two different occasions and training did not appear to affect the index, although differences between the two estimates increased as the value of the first estimate increased. Mean overall response latency did not correlate significantly with intelligence and measures obtained from retarded subjects were very like those reported in similar experimental situations utilizing normal subjects. This unexpected finding is interpreted as suggesting that, in this situation, retarded subjects have been prepared to respond on the basis of less evidence than is usually required by intellectually normal subjects.

Evidence of an early information processing speed deficit in unipolar major depression

“…The DT\MT paradigm is also constrained by subjects being able to adopt varying speed-accuracy trade-off strategies, as accuracy can be increased at the expense of response time. Unlike RT procedures the inspection time (IT) procedure is widely regarded as a measure of the speed of early stages of information processing that is not sensitive to motor speed, speed-accuracy tradeoffs or other cognitive strategies (Nettelbeck, 1987 ;Deary & Stough, 1996). Avoiding tasks in which strategies can improve performance is crucial in assessing cognition in depression, as depressed individuals are often impaired in the deployment of effective cognitive strategies (Channon & Green, 1999).…”

“…IT is a measure defined as the minimum duration of stimulus presentation required for near perfect response on a two-choice visual discrimination task. The stimulus duration is controlled by superimposing a backward mask over the stimulus which prevents extended iconic sampling (Nettelbeck, 1987). Subjects are instructed to take as long as necessary to respond, and to focus on accuracy.…”

Advances in the assessment of cognitive skills using computer-based measurement

“…When prompted, the subject still lifts his finger as quickly as possible off the home button (reaction time), but he or she is now required to press a second button that is paired with the light (movement time). Research utilizing the Hick paradigm has consistently confirmed what has come to be known as Hick's law: Reaction time increases linearly as a function of the number of bits of information (lights to choose from) made available to the subject (Bates & Rock, 2004;Deary & Stough, 1996;Jensen, 1982;Nettelbeck, 1987;Vernon, 1987).…”

“…The selection of these elementary tasks is typically based on the assumption that they are so simple or elemental in nature that any subject could solve the tasks, given unlimited time. While Vickers is typically credited with the original theoretical development of cognitive speed or inspection time (IT) research, one of his doctoral students, Nettelbeck, conducted some of the earliest empirical studies (Nettelbeck & Lally 1976). Although the theoretical rationale underlying this field of research is almost 30 years old (Vickers, 1970(Vickers, , 1979, the sophistication and accuracy of empirical studies has paralleled advances in technology and has been born of cross-disciplinary discussion and collaboration.…”

Models and Paradigms in Personality and Intelligence Research

“…In both versions, an aspect of exposure time is varied using some accepted psychophysical procedure, and the score is the minimum time needed to detect the difference between two simple stimuli. In the visual IT task, the stimuli consist of two simultaneously presented lines that differ in length (see Nettleback & Lally, 1976). …”