Figure 5. The “2 down – 1 up” adaptive level variation rule used for micromelody discrimination training.

For every two correct discrimination trials, the size of the micromelody interval decreased by one level (e.g., 60 c to 50 c), thus making the discrimination task more difficult. If a trial was answered incorrectly, the micromelody interval increased by one level. After four reversals of difficulty level, 70 trials of training for finer discrimination began at the interval scale that elicited the fourth reversal (indicated in dark gray). During this finer discrimination training, the adaptive-level rule was applied again, but each level was separated by only two cents.