Gender differences were examined in performance on the California Verbal Learning Test (immediate and delayed recall), Digit Span Backwards, Symbol-Digit Modalities Test, Spot-the-Word, and simple and choice reaction time. The data came from a community survey involving 2404 people aged 20-24 years, 2530 aged 40-44 years, and 2551 aged 60-64 years. Males performed better on Digit Span Backwards and on reaction time, while females were better on recall and Symbol-Digit Modalities Test. A range of sociodemographic, health state, and health habit variables were examined as possible mediators of these gender differences. Mediating effects were found for education, non-English speaking background, depressive symptoms, alcohol abstinence or occasional use, low physical activity, heavy cannabis use, and pulmonary function. When mediating variables were controlled, gender differences tended to disappear on tests for which there was a male advantage and to magnify on tests for which there was a female advantage.