Learning two things at once: differential constraints on the acquisition and consolidation of perceptual learning.

Learning is often prevented by events that occur after training, an outcome that is usually attributed to the disruption of consolidation-the transfer of learning to long-term memory. Here, we provide evidence from perceptual learning that improvements in performance can also be blocked by intervening events that occur during the acquisition phase of learning-the period of active practice. Listeners improved on each of two conditions of auditory temporal-interval discrimination (100 and 350 ms) when the two were practiced consecutively, even though that is a classic disruption-of-consolidation regimen. However, when practice on these two conditions was interleaved, there was no learning on either condition. The failure to improve in the interleaved case indicates that, at least in some circumstances, learning can be prevented during acquisition by events that do not disrupt consolidation itself. These results thus suggest that acquisition and consolidation are distinct phases in human learning.