Figure 2
Post-treatment nicotine and placebo differences as a function of pre-treatment baseline performance in three experiments. (a) Frequency discrimination for young (blue circles) and elderly (red circles) adults. The baseline-dependent regression line is represented by the dotted line, with the linear regression equation being shown by text in the bottom (top line), r2 and p-value (second from top). The nicotine effect in terms of the mean difference between post-nicotine and post-placebo performance is represented by the dashed horizontal line, with the mean difference, standard deviation and the two-sample t-test result being shown by text in the bottom. The solid horizontal line crossing zero on the y-axis indicates no difference between post-nicotine and post-placebo performance. (b) Frequency modulation identification results are displayed following the same convention as (a). (c) Intensity discrimination results are displayed following the same convention as (a). The asterisk next to the dashed line indicates a significant difference from the baseline (solid line) and that next to the dotted indicates significant regression.
