A choice assessment was used to categorize reinforcers as high, middle, and low preference with 4 males (ages 7 to 19) with multiple disabilities including severe/profound mental retardation. High-preference stimuli consistently functioned as reinforcers for all subjects whereas low-preference stimuli did not function as reinforcers. (Author/DB)

The first of two studies with two adolescent students with serious emotional disturbances examined the interaction between unequal rates of reinforcement and equal versus unequal delays to reinforcer access on performance of math problems. The second study examined the interactive effects of reinforcer rate, quality, and delay. (Author/DB)