The relationship of cortisol to practice-related gains in intelligence among older persons

Based on data collected from two separate samples of older adults, the present study explored the role of cortisol in mediating practice-related gains in fluid intelligence (Gf) among older adults. Analyses across samples involved treatment group participants who received stress inoculation training in order to reduce anxiety concerning intellectual performance; waiting list control group participants did not receive training until the experiment(s) were completed. Practice effects were examined for both groups. In Study 1, the sample consisted of a heterogeneous (re: concerns about intellectual performance) group of older adults, and Study 2 participants were older adults who self-reported as being at least moderately anxious or concerned about intellectual performance declines. The two samples differed on health (p < .01), with Study 2 participants being healthier (as determined via self-report). Results indicated that practice, but not training, effects were evident for measures of crystallized ability (Gc) and Gf across both studies. The data also suggested that cortisol mediation was different for the two samples in that it was negatively correlated with Gf in the first sample, and, though not significant, positively correlated with Gf in the second. The same directional relationships were evident for the measure of Gc. Comparisons between studies regarding correlations between cortisol and practice-related gains in performance were significant for Gf (p < .01) and approached significance for Gc (p < .07). These data seem to suggest that for some older persons, higher levels of cortisol interfere with the effects of practice on Gf performance, while for others, higher cortisol facilitates such gains in performance.