Jensen box

The Jensen box was developed by University of California, Berkeley psychologist Arthur Jensen as a standard apparatus for measuring choice reaction time, especially in relationship to differences in intelligence. Since Jensen created this approach, correlations between simple and choice reaction time have been demonstrated in many hundreds of studies. Perhaps the best was reported by Ian Deary and colleagues, in a population-based cohort study of 900 individuals, demonstrating correlations between IQ and simple choice reaction time of –0.3 and –0.5 respectively, and of –0.26 with the degree of variation between trials shown by an individual. The Jensen box was also used on the Odd Man Out test.

The standard box is around 20 inches wide and 12 deep, with a sloping face on which 8 buttons are arrayed in a semicircle, with a 'home' key in the lower center. Above each response button lies a small LED which can be illuminated, and the box contains a loudspeaker to play alerting sounds. Typically, following a warning tone and a delay, the light next to one of the one to eight displayed buttons comes on and the subject releases their finger from the home button to press the button with the light. Times from light on to release (RT) and from release to press (movement time) are measured.

Following Hick's law, reaction times (RTs) slow as a log₂ of the number of choices that are presented. Thus when all but one button are covered responses are fastest, and slowest when all 8 responses are available.

Several parameters can be extracted: The mean 1-choice RT gives simple reaction time. The slope of the function across 1, 2, 4, and 8 lights gives the rate of information processing, and variance or standard deviation in RTs can be extracted to give a measure of response variability within subjects.

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