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Erik Blaser, Zsuzsa Kaldy, Marisa Biondi; Measuring VSTM ‘iconic’ memory capacity in 6-month-old infants. Journal of Vision 2009;9(8):603. doi: https://doi.org/10.1167/9.8.603.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: ‘Whole report’ tests underestimate memory capacity; the crucial innovation was the partial report (Sperling, 1960). However, typical same/different tests of infants' memory - where infants' reactions are tested when a change is made to a set of objects, say, while briefly occluded or invisible - amount to whole report. Purpose: Adapt and apply a partial report test of infants' very short term (VSTM), ‘iconic’ memory span. Method: Over two blocks of 20 trials, ten infants (age range: 5;0–6;30) were presented with a set of 4 identically-shaped, but differently-colored items, spaced symmetrically around central fixation. After a 1 second exposure, a randomly chosen pair of neighboring items disappeared. After 500 msec, the two items reappeared, always with one changed to a new color and the other unchanged. This display remained for 2 seconds (eye-movements were recorded throughout the trial with a Tobii eye tracker). The sudden offset of the two items itself was the partial report post-cue, designed to draw attention and trigger their coding from VSTM into more durable short-term memory. Only by remembering all items in the set would infants be able to distinguish between the changed vs. unchanged items. Results: In what amounts to a 2AFC, we measured which of the two items was 1) fixated more frequently and 2) for a greater total time. For a set size of 4, infants showed positive ‘novelty’ effects, looking more often and longer at the changed item. Preliminary tests with set size 6 suggest positive results as well. Conclusion: We created a partial report paradigm for infants. Infants remembered two items cued randomly from a set of 4 (with suggestive results from set size 6, and work with higher set sizes ongoing), indicating a capacity of VSTM iconic memory of at least 4 items.
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