Counterintuitively, Y. Kareev, I. Lieberman, and M. Lev (1997) found that a lower short-term memory capacity benefits performance on a correlation detection task. They assumed that people with low short-term memory capacity (low spans) perceived the correlations as more extreme because they relied on smaller samples, which are known to exaggerate correlations. The authors consider, as an alternative hypothesis, that low spans do not perceive exaggerated correlations but make simpler predictions. Modeling both hypotheses in ACT-R demonstrates that simpler predictions impair performance if the environment changes, whereas a more exaggerated perception of correlation is advantageous to detect a change. Congruent with differences in the way participants make predictions, 2 experiments revealed a low capacity advantage before the environment changes but a high capacity advantage afterward, although this pattern of results surprisingly only existed for men.