Temporal factors in visual perception: A differential approach

The tradition in sensory and perceptual psychology is not to pay much attention to individual differences but to focus almost exclusively on normative or generic processes. Nevertheless, consistent individual differences may exist in sensory and perceptual processes, just as they do in all other areas of human behavior where their existence has been investigated. A preliminary study was made of flicker fusion frequency, apparent movement, and three other perceptual tasks as differential measures. With one exception, Letter Search, all of the tests were psychophysical rather than cognitive. All had to do with time; that is, perceptual speed mattered in all of them. The analysis focused on reliability, in the sense of consistency from trial to trial. Four of the five tests showed good reliabilities in this sense, white the fifth was borderline. In one test, Bistable Stroboscopic Motion, the dependent measure, interstimulus interval, showed a consistent though shallow tendency to lengthen with practice. In the remaining four tests practice effects were largely confined to the first two administrations.