Effects of a freely available response on the schedule performance of mentally retarded persons.

The effects of a freely available response on the schedule performance of 84 mentally retarded persons were examined in a laboratory setting. Instrumental performance exceeded performance of the free response in contingent schedules; the opposite occurred in noncontingent schedules. Also, instrumental performance decreased whereas responding on the free response increased across increasing probability levels of the freely available response. We concluded that increases of instrumental performance in the response deprivation schedules employed were due to the contingency and not noncontingent deprivation and that the effectiveness of therapeutic reinforcement programs is influenced by the presence of alternative responses.