Learning curves for training at a base interval of 75 msec. A, Individual subject thresholds, expressed as Weber fractions, plotted as a function of training sessions. Stimuli were delivered to the distal tip of the fourth digit for subjectsS13–S16. Bars are SEM within subjects. Thefilled symbols indicate pre- and post-test thresholds for each subject. Note that the pre- and post-test thresholds were estimated from five to six blocks of 60 trials, whereas training thresholds were obtained for 15 blocks. B, Mean of all four subjects plotted as a function of training days. Here, error bars represent 1 SEM across subjects.