Perceptual learning is slower in adolescence. A, Experimental timeline for perceptual training. Ages depicted here are exact for young animals, and approximate for adolescent and adult animals (for details, see Materials and Methods). B, During perceptual training, warn trials consisted of AM noise across a wide range of depths. Depths are presented in decibels relative to 100%, such that 0 dB is fully modulated noise. C, A representative psychometric function from the first day of perceptual training is plotted for one adolescent (subject ID 203447). Threshold was calculated as the AM depth at which the fitted function crossed d′ = 1 (dashed line). D, Perceptual learning trajectories are plotted for each age group as a function of the log of the perceptual training day. Individual trajectories are indicated by thin lines. Squares and error bars represent the mean ± SEM values; thick straight lines represent the linear regressions. The slope, Pearson's r, and statistical significance for each fit is presented in the top right corner of each plot. The number of subjects in each group is indicated above each panel. Note that for visual clarity, the y-axes are truncated at −20 dB; however, four data points fell outside this limit: one young point (day 3, −24.2 dB), one adolescent point (day 2, −25.6 dB), and two adult points (days 9 and 10, −22.4 and −22.7 dB). E, Bootstrapped slope distributions are plotted for each age group. See text for statistical details. unmod, Unmodulated noise.