iconic

Meaning: Iconic memory is the sensory register for vision. It holds a detailed copy of a visual scene for a fraction of a second (roughly 0.25 to 0.5 s in most accounts). If attention does not pass the information on to short-term (working) memory, it decays. Its capacity is large, but it fades too fast for most of it to be reported. Its auditory counterpart is echoic memory, which lasts longer, on the order of a few seconds.

On the MCAT: The classic setup is Sperling's partial-report experiment. A grid of letters is flashed for a very short time. In whole report, participants recall only about 4 or 5 letters. In partial report, a tone right after the flash cues which row to report, and recall of that row is high. This implies the whole grid was briefly available. If the cue is delayed by about a second, accuracy falls toward the whole-report level, which shows rapid decay. Expect questions that ask you to predict how recall changes with cue delay, or to name the memory stage involved.

Common confusion: Students read low whole-report recall as meaning little was stored. The partial-report result shows the limit comes from the image fading during recall, not from poor initial storage. Also keep iconic (visual, under a second) separate from echoic (auditory, a few seconds) and from working memory, which holds roughly 7 ± 2 items.