PLE and working memory
Although caffeine did not significantly influence PLE or WM, to compare the effects of caffeine and dexamphetamine we conducted the same correlation analysis. Changes in PLE scores (caffeine–placebo) were correlated with WM (maximum obtained) change scores (caffeine–placebo). There were no significant correlations between caffeine induced changes in PLE and changes in WM (r = -0.19, p = 0.40, n = 20), SWM (r = -0.11, p = 0.65, n = 20), VWM (r = -0.20, p = 0.38, n = 20). There was also no significant correlation between caffeine induced changes in PLE and changes in WM at each delay: the 0 s (r = -0.18, p = 0.44, n = 20), but not at 4 s (r = -0.25, p = 0.27, n = 20), 6 s (r = -0.23, p = 0.32, n = 20), and 8 s (r = 0.05, p = 0.84, n = 20).