Perceptual learning: how much daily training is enough?

The acquisition of many perceptual skills proceeds over a course of days. However, little is known about how much daily training is needed for such learning to occur. Here we investigated this question by examining how varying the number of training trials per day affected learning over multiple days on two auditory discrimination tasks: frequency discrimination and temporal-interval discrimination. For each task, we compared improvements in discrimination thresholds between different groups of listeners who were trained for either 360 or 900 trials per day for 6 days. Improvement on frequency discrimination required >360 trials of training per day while learning on temporal-interval discrimination occurred with 360 training trials per day, and additional daily practice did not increase the amount of improvement. It therefore appears that the accumulation of improvement over days on auditory discrimination tasks may require some critical amount of training per day, that training beyond that critical amount yields no additional learning on the trained condition, and that the critical amount of training needed varies across tasks. These results imply that perceptual skills are transferred from short- to long-term memory (consolidated) daily, but only if a task-specific initiation requirement has been met.