Comparison of reinforcement schedules in the reduction of stereotypy with supported routines.
Use fixed-ratio token delivery during fast vocational tasks to keep stereotypy low in teens with severe ID.
01Research in Context
What this study did
Clarke et al. (1998) compared two token schedules during vocational tasks for teens with severe intellectual disability. One schedule gave a token after every few correct parts (fixed-ratio). The other gave tokens at random times (variable-interval). The team flipped the schedules across days to see which kept stereotypy lower.
What they found
Fixed-ratio tokens kept stereotypy from starting better than variable-interval tokens. Teens stayed focused on the job when they knew the next token came after a set amount of work.
How this fits with other research
Attwood et al. (1988) saw the opposite pattern in adults. Long, slow fixed-interval schedules made stereotypy shoot up. The key difference is pace: the 1998 study used quick fixed-ratio work cycles, while the 1988 study stretched the wait time to three minutes. Same label “fixed,” but very different timing.
Van Houten et al. (1980) also found variable-ratio beat fixed-ratio for attention and math work in deaf students. Again, the task mattered: math problems moved fast, so the unpredictability kept kids engaged rather than restless.
Tassé et al. (2013) showed variable-interval can cut vocal stereotypy in a young child with autism. The schedule was paired with reinforcing sitting, not vocational output, showing VI works when the goal is calm presence, not piece-work speed.
Why it matters
Pick the schedule that matches the job speed. For assembly or sorting tasks that move quickly, stick with fixed-ratio tokens. The clear work-to-token link keeps hands busy and stereotypy quiet. Save variable-interval for times you want steady calm, not fast output.
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02At a glance
03Original abstract
The rates and durations of stereotypic behaviors in four adolescents with severe mental retardation were measured during two daily vocational training sessions and during contiguous periods of leisure in their special education classrooms. Vocational training was conducted in two different tasks, alternating across days. The task requirements for each participant were matched to each participant's learning and performance characteristics. The participants were exposed to a fixed ratio schedule of tokens exchangeable for food items on one task and to a variable interval schedule for the same consequences on the second task. The schedules were chosen as an initial test of a matching-law based prediction by Myerson and Hale (1984): Variable interval reinforcement for adaptive behavior will produce less allocation of responding to maladaptive behavior than will a ratio-based intervention. When work performances stabilized, the schedules of token delivery were reversed across the tasks and performances again stabilized. Results are reported for periods when work performances met stability criteria. Stereotypy occurred more during leisure than during vocational training under either schedule. The major differences in stereotypy between leisure and vocational training were differences in episode length rather than rate of onset. Onset of stereotypy in vocational training, however, occurred at higher rates under the interval schedule than under the ratio schedule in both tasks. The results are discussed in terms of Myerson and Hale's prediction and implications for further research and application.
Research in developmental disabilities, 1998 · doi:10.1016/s0891-4222(97)00045-0