Imagine several colored stars appear in front of you for 1 second, how many stars can you remember and tell its color based on that one glance? Do you know if you can perform better than a 6-month-old infant in this test? We may get an answer from this study in which psychologists for the first time measured infants’ iconic memory.
Iconic memory is the initial 0.2 to 0.5 seconds after you visually perceive an item. Have you ever tried to look at the list of side effects displayed so quickly in some pharmaceutical commercials? Without the ability to recall much, you only got a feeling that you have seen more than you could remember. That is a close example of the feelings of iconic memory.
Iconic memory is the first stage of our memory, followed by short-term memory and long-term memory. If you imagine the long-term memory to be a library that can hold extremely large amount of information for almost a life-long time, then the short-term memory is like a librarian working at the front-desk holding a limited number of items and selects which item to be stored. The iconic memory is comparable to a pair of wide-angle video-capturing glasses in front of the librarian’s eyes, storing images for 0.2 to 0.5 seconds. The glasses have a similarly limited capacity just like the librarian, but usually capture something that the librarian cannot see nor process.
The measurement of adults’ iconic memory is based on the partial report method. For example, after an alphanumeric array of nine items was presented and removed, participants were cued to report a random subset of their memory (e.g. a low-pitched tone as the cue for a report of the lower of the three rows of letters). Accurate partial report indicates that all items presented has been stored, even though the participants could only report three to four items if asked to give a whole report of what they saw. Being invented in the 1960s, the partial report method revealed a high-capacity (9 items) and fast-decaying (0.2s to 0.5s) iconic memory in adults.
Fifty years later, Blaser and Kaldy became the first to ask infants for a partial report. Six-months-old infants were tested with presentations of colored stars and eye-tracking devices. In each trial of presentation, infants first watched an 8.5 second animation followed by a 1 second fixation cross to capture their attention to the center of the screen. A set of 2, 4, 6, 8, or 10 colored stars then appeared (each infant always saw a given set of stars). After displaying for 1 second, two neighboring stars disappeared for 0.5 second, which served as the cue in the partial report. The two stars reappear and one was changed in color. Infants’ iconic memory was then tested by preferential looking: correct memory is indicated by infants’ longer gaze at the star with a changed color.
How many colored stars did infants remember then? The answer is 5.
How about adults’ performance using the same method? The answer is 5.75.
The nearly matched capacities of infants and adults strike the researchers as signs of a rapid maturity of iconic memory. So, if you ever find yourself in an iconic memory competition against a 6-months-old, better stop laughing and hope you are on a good day.
Blaser E, & Kaldy Z (2010). Infants get five stars on iconic memory tests: a partial-report test of 6-month-old infants’ iconic memory capacity. Psychological science : a journal of the American Psychological Society / APS, 21 (11), 1643-5 PMID: 20923928