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.