Assessing correspondence following acquisition of an exchange-based communication system.

Two students with developmental disabilities were taught to request six snack items. Requesting involved giving a graphic symbol to the trainer in exchange for the matching snack item. Following acquisition, we assessed the correspondence between requests and subsequent item selections by requiring the student to select the previously requested snack item from an array containing all six items. The effects of acquisition training were evaluated in a multiple-probe across subjects design. Acquisition was achieved in from 9 to 29 trials per item. Following acquisition, Jason showed a high level of correspondence between requesting and selecting, but Ryan required additional training to achieve correspondence. These data support the use of exchange-based communication systems, but suggest that some students may require explicit correspondence training.