Learning, worsening, and generalization in response to auditory perceptual training during adolescence

Abstract

While it is commonly held that the capacity to learn is greatest in the young, there have been few direct comparisons of the response to training across age groups. Here, adolescents (11-17 years, n = 20) and adults (≥18 years, n = 11) practiced detecting a backward-masked tone for ∼1 h/day for 10 days. Nearly every adult, but only half of the adolescents improved across sessions, and the adolescents who learned did so more slowly than adults. Nevertheless, the adolescent and adult learners showed the same generalization pattern, improving on untrained backward- but not forward- or simultaneous-masking conditions. Another subset of adolescents (n = 6) actually got worse on the trained condition. This worsening, unlike learning, generalized to an untrained forward-masking, but not backward-masking condition. Within sessions, both age groups got worse, but the worsening was greater for adolescents. These maturational changes in the response to training largely followed those previously reported for temporal-interval discrimination. Overall, the results suggest that late-maturing processes affect the response to perceptual training and that some of these processes may be shared between tasks. Further, the different developmental rates for learning and generalization, and different generalization patterns for learning and worsening imply that learning, generalization, and worsening may have different origins.

Figures

Figure 1

Across-session performance on the trained backward-masking condition. (a)–(c) Mean results by age group: mean signal detection thresholds (dB for 94.2% correct) for the trained (filled circles) and control (open circles) groups at the pre- and post-tests, and for the trained groups during the training phase. Results are shown separately for the (a) adults (≥18 years of age), (b) older adolescents (13 years, 4 months–17 years, 1 month), and (c) younger adolescents (11 years, 0 months–13 years, 2 months). Trained groups: adults, n = 11; older adolescents, n = 11; younger adolescents, n = 9. Control groups: adults, n = 19; older adolescents, n = 13; younger adolescents, n = 15. (d) Learners vs non-learners: mean signal detection thresholds for the combined group of younger and older adolescents, divided into learners (filled triangles, n = 10), worseners (filled hourglasses, n = 6), and non-learners (filled squares, n = 4) based on each listener's performance across all 12 sessions. Error bars indicate +/− one standard error. Only the upper or lower error bar is shown when the error bars overlapped between groups.

Figure 2

Within-session performance on the trained backward-masking condition. (a)–(d) Mean threshold values from early (estimates 1–6) and late (estimates 19–24) during each training session. Results are shown separately for the (a) adult learners (n = 10) and each group of adolescents: (b) learners (n = 10), (c) worseners (n = 6), and (d) non-learners (n = 4). (e) Change in threshold (late minus early threshold estimates) averaged across the training sessions for each of the four trained groups. Error bars indicate +/− one standard error.

Figure 3

Pre- and post-test performance of learners and controls on the trained and untrained conditions. Signal detection thresholds (dB for 94.2% correct) for adult and adolescent learners (filled triangles) and controls (open circles) on (a) the trained backward-masking condition and (b)–(f) the five untrained masking conditions. Note that due to the variability in thresholds across conditions, the range of the axes is different for each condition. Condition labels and schematics are shown in the 1st column. Asterisks mark the conditions on which the learners improved more than same-age controls. Mean data (2nd column): Post-test thresholds for each group after adjusting for pre-test thresholds using IBM-SPSS Statistics 20. Error bars indicate +/− one standard error and the dashed horizontal line indicates the average pre-test threshold across all four groups. Individual data (3rd and 4th columns): pre- and post-test thresholds for individual listeners. The dotted diagonal line in each panel has a slope of 1, indicating equivalent performance on the pre- and post-tests. Points below this line therefore represent individuals who improved while points above this line represent individuals who got worse.

Figure 4

Pre- and post-test performance for worseners, non-learners, and controls on the trained and untrained conditions. As in Fig. 3, but for the three conditions completed by all of the adolescent worseners (filled hourglasses), non-learners (filled squares), and controls (open circles). Asterisks mark the conditions on which the post-test thresholds of the worseners were significantly higher than those of controls. Note that the range of values on the axes varies across conditions.