The number of stimuli to be related in equivalent classes was manipulated to evaluate the effect of class size on its occurrence and maintenance. Forty undergraduate students distributed in four groups were taught, by the matching-to-sample procedure, to select arbitrary stimuli to set up relationships in three equivalent classes. The classes had three, four, five or six members, according to the group. Equivalence relations tests were applied immediately after the trainings and after a period of six weeks. The results showed that the class size did not affect the likelihood of equivalence class establishment. However, the probability of maintenance and reestablishment of relations weakened during the period, was related to the class size. It was concluded that the maintenance and reestablishment of the classes were facilitated when they had a larger number of members.
Stimulus equivalence; undergraduate students; conditional discrimination
