EMERGENCE OF REINFORCER PREFERENCE AS A FUNCTION OF SCHEDULE REQUIREMENTS AND STIMULUS SIMILARITY

Tustin (1994) recently observed that an individual's preference for on e of two concurrently available reinforcers under low schedule require ments (concurrent fixed-ratio [FR] 1) switched to the other reinforcer when the schedule requirements were high (concurrent FR 10). We exten ded this line of research by examining preference for similar and diss imilar reinforcers (i.e., those affecting the same sensory modality an d those affecting different sensory modalities). Two individuals with developmental disabilities were exposed to an arrangement in which pre ssing two different panels produced two different reinforcers accordin g to progressively increasing, concurrent-ratio schedules. When two di ssimilar stimuli were concurrently available (food and a leisure item) , no clear preference for one item over the other was observed, regard less of the FR schedules in effect (FR 1, 2, 5, 10, and 20). By contra st, when two similar stimuli were concurrently available (two food ite ms), a clear preference for one item emerged as the schedule requireme nts were increased from FR 1 to FR 5 or FR 10. These results are discu ssed in terms of implications for conducting preference assessments an d for selecting reinforcers to be used under training conditions in wh ich response requirements are relatively high or effortful.