Training can improve perceptual sensitivities. We examined whether the temporal dynamics and the incidental versus intentional nature of training are important. Within the context of a birdsong rate discrimination task, we examined whether the sequencing of pretesting exposure to the stimuli mattered. Easy-to-hard (progressive) sequencing of stimuli during preexposure led to a more accurate performance with the critical difficult contrast and greater generalization to new contrasts in the task, compared with equally variable training in either a random or an antiprogressive order. This greater accuracy was also evident when participants experienced the progressively sequenced stimuli in a different incidental learning task that did not involve direct auditory training. The results clearly show the importance of temporal dynamics (sequencing) in learning and show that the progressive training advantages cannot be fully explained by direct associations between stimulus features and the corresponding responses. The current findings are consistent with a hierarchical account of perceptual learning, among other possibilities, but not with explanations that focus on stimulus variability. (Contains 1 figure, 2 tables and 8 footnotes.)