Abstract

Based on the experimental observation that span-length lists take about two seconds to articulate, experimenters have conjectured that the verbal short-term memory trace lasts about two seconds. However, this two-second decay conjecture is inconsistent with other experimental data, and a mathematical model that offered support for this conjecture actually estimates the lifetime of an intact list of words, rather than that of individual words from a list. To illustrate this point, I present an item-based model of trace decay which demonstrates that the duration of the short-term memory trace must be longer than the time taken to articulate a spanlength list. For a set of words whose span-length lists can be rapidly articulated in about two seconds, the model offers a conservative estimate for their mean decay times of about four seconds. Key words: short-term memory decay In their influential paper on verbal short-term memory, Baddeley, Thomson, and Buchanan (1975) reported the articulatory duration effect in verbal shortterm memory, in which lists comprised of shorter words are recalled more accurately than equal-length lists of longer words. They noted that the number of words that could be remembered (out of five) was equal to the number that could be articulated in about 1.5 seconds (across experiments and participants, their estimates ranged between 0.93 and 1.95 s). This result was later bolstered by the results of Standing, Bond, Smith, and Isely (1980), who showed that across a wide variety of stimuli and experimental conditions, the time it took to subvocalize memory-span length lists was between about 1.7 and 2.1 seconds. These behavioral findings suggest that information decays from short-term memory with time, and provided strong evidence for the articulatory loop

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