Hypothesis generation, probability judgment, and individual differences in working memory capacity.

This research examined the role of working memory (WM) in probability judgment and hypothesis generation using a simulated task that involved estimating the likelihood that particular menu items would be ordered by customers at a dinner. Five main findings were observed. First, judgments of the likelihood of individual items were made relative to alternatives retrieved from long-term memory. Second, the number of alternatives retrieved was positively correlated with a measure of WM-capacity (the operation-span task). Third, participants' probability judgments were subadditive (summing to well over 100%). Fourth, the degree to which participants' judgments were subadditive was affected by the number and strength of the alternatives retrieved from long-term memory. Fifth, the degree to which participants were subadditive was negatively correlated with WM-capacity. The results suggest that individual differences in WM-capacity are fundamental to hypothesis generation and probability judgment.