Assessment of stimuli controlling the requests of students with severe mental retardation during a snack routine

This study assessed stimuli controlling requests during a snack routine after extensive request training with a delayed prompt procedure. During training sessions, one of three three-item snack groups was presented to 3 subjects with severe mental retardation. Assessment sessions involved (a) training conditions (all items were visible), (b) presenting two of three items from a particular group, or (c) presenting no items. One subject requested food items when no food items were present, 2 frequently requested a missing item when the two other items were visible, and all subjects requested visible items. Procedures for assessing stimulus control, such as those described in the current paper, should lead to a better understanding of the variables controlling behaviors that initially appear perplexing and unpredictable.