TABLE 1.

Discrimination training steps.

Discrimination	Max. number		Correction
training	of trials	Criterion	trials
1	50	≥5 sessions, completion of 50 trials in ≤20 min. in last two sessions	no
2	20	80% correct responses in two consecutive sessions	yes
3	50	80% correct responses in two consecutive sessions	yes
4	50	80% correct responses in one session	no
5	50	≥3 sessions, 80% correct responses in last two sessions	no

Training consisted of 5 steps. Training sessions ended after 30 min, unless the maximum number of trials was reached before that time. Upon incorrect touches, correction trials (i.e., repeated presentation of the same trial until a correct touch) were presented (not included in the total trial count).