SPARE THE ROD AND SPOIL THE ICON

Short-term visual storage was investigated with a successive field paradigm, so that correct performance depended on combining visual information from 2 targets that were never on simultaneously. Five college Ss took part in 3 experiments. In the 1st 2 experiments, the stimuli consisted of 2 slides, each containing a 10′ red dot on a gray surround, and separated by an interstimulus interval (ISI) from 20 to 400 msec. Ss had to determine if the dots were vertically or horizontally aligned. In Exp I, the stimuli had either no contrast for the rods or no luminance contrast for the cones or high contrast. At short ISIs the cone contrast determined performance, whereas at long ISIs the rod contrast determined performance. In fact, when the dots were invisible to the rods, the task was impossible for long ISIs. In Exp II, performance was compared for zero log rod contrast and for small departures from zero. Even a small departure from zero log rod contrast resulted in above-chance performance. In Exp III, the stimuli were luminous rectangles, and the task was to decide whether or not a 4′ spatial gap was present between the 2 successively presented rectangles. Wavelength, luminance, and ISI were varied under both photopic and scotopic adapting conditions. The result was that the rods performed the task for ISIs of 150 msec or longer under scotopic conditions and under the photopic conditions tested. Results of the experiments taken together are consistent with the hypothesis that the cone icon is short, whereas the rod icon is robust and long lasting. (18 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1979 American Psychological Association.