What’s shorter than short-term memory? The answer is iconic memory, the very accurate but very short-lived visual impression of something. Here’s the thing about iconic memory: It’s so fleeting that it’s difficult even to detect—by the time you could verbally report something stored in only iconic memory, it’s gone. So to test iconic memory, psychologist George Sperling came up with a tricky experiment: He asked participants to look very briefly at a grid of letters. Short-term memory should have allowed them to report four to six characters and, in fact, this is what Sperling found. But it turned out that immediately after glimpsing the grid, participants could reproduce any four-to-six character section of the grid—yes, their recall was restricted by the limits of short-term memory, but their iconic memory briefly held the whole thing in their minds.
(By the way, can you find the one common word in this entry’s heading doodle?)