T hree ways in which a visual stimulus lives on in its observer after its physical offset were distinguished by Coltheart (1980): The neurons of low-level vision excited by any stimulus continue to re •
after the stimulus has gone. This may be called neural persistence, and it is studied by single-cell recording and other electrophysiological measurement techniques. A stimulus continues to be visible to the observer for some time after • its physical offset. This may be called visible persistence, and a variety of methods are available for studying it: Coltheart (1980, pp. 188-205) lists seven of these and reviews results obtained with each. Visible persistence is, of course, visible; it is also short-lived. Its lifetime, as measured from stimulus offset, is inversely related to stimulus duration and stimulus energy. Information contained in a stimulus (such as the identity of letters when • the stimulus is an array of letters) can still be processed for some time after stimulus offset This may be called informational persistence, and it is studied by the partial-report technique rst used extensively by Sperling (1960). Informational persistence is not visible; like visible persistence, it is short-lived and of high capacity, but unlike visible persistence, its duration is unaffected by stimulus duration or stimulus energy.