Recently, Vul and Pashler (2008) demonstrated that the average of 2 responses from a single subject to general knowledge questions was more accurate than either single estimate. Importantly, this reveals that each guess contributes unique evidence relevant to the decision, contrary to views that eschew probabilistic representations of the evidence-gathering and decision-making processes. We tested an implication of that view by evaluating this effect separately in individuals with a range of memory spans. If memory span is the buffer in which retrieved information is assembled into an evaluation, then multiple estimates in individuals with lower memory spans should exhibit greater independence from one another than in individuals with higher spans. Our results supported this theory by showing that averaging 2 guesses from lower span individuals is more beneficial than averaging 2 guesses from higher span individuals. These results demonstrate a rare circumstance in which lower memory span confers a relative advantage on a cognitive task.
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