Inspection time refers to the exposure duration required for a human subject 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 (similar to the Greek letter Pi).
[2] 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.
[3] Ted Nettelbeck, Chris Brand and others demonstrated it related quite strongly to psychometric intelligence, especially across the lower part of the IQ range [2][4] suggesting that differences in intelligence may reflect, in part, differences in the rate of information processing - a theory proposed by Arthur Jensen.
[5] 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).