Overlap between visual inspection time tasks and general intelligence

The stimulus display duration required for subjects to accurately compare the length of two line lengths (known as Inspection Time: IT), reliably correlates around 0.5 with general intelligence. It is not clear, however, if this correlation reflects general “speed of processing”, or some other element of the task. There is a consequent need for new experimental paradigms. We describe a novel IT task where participants viewed a sequence of eight briefly-presented coincident coloured circles, the first of which was presented for a variable duration. Participants reported the colour of the first circle. The threshold for perceiving this colour correlated 0.37 and 0.38 (p < 0.05) with two conventional IT tasks within a sample of 75 students. It also correlated significantly with scores on a timed measure of the Raven's Advanced Progressive Matrices (r = − 0.39, p < 0.01). The implications of these results for the validity of the concept of IT are discussed.