Within-session changes in responding during concurrent schedules with different reinforcers in the components.
Choice bias fades within the same session when each schedule pays a different reinforcer, so keep preference tests short.
01Research in Context
What this study did
The team ran a single-case lab study. They set up two schedules side-by-side in one session.
Each side delivered a different reinforcer. They watched how choice drifted as the minutes passed.
What they found
Bias and sensitivity to reinforcement both faded within the same session.
The data did not fit a simple "arousal drops over time" story.
How this fits with other research
Silverman et al. (1994) saw the same drift under simple schedules. The new paper shows the problem gets worse when each schedule pays a different reward.
Buitelaar et al. (1999) later added demand curves and confirmed the lesson: short sessions keep measures clean.
Lander et al. (1968) proved that response ratios normally lock to reinforcer ratios. The 1996 findings warn that this lock can loosen before the session ends.
Why it matters
If you run concurrent-operant preference assessments, keep them brief. When each option delivers a unique reinforcer, within-session drift can hide true preference. Run five-minute loops, reset, and re-present the array instead of one long ten-minute block. Your data will match the child's real choice better.
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02At a glance
03Original abstract
Rats and pigeons responded on several concurrent schedules that provided different reinforcers in the two components (food and water for rats, Experiment 1; wheat and mixed grain for pigeons, Experiment 2). The rate of responding and the time spent responding on each component usually changed within the session. The within-session changes in response rates and time spent responding usually followed different patterns for the two components of a concurrent schedule. For most subjects, the bias and sensitivity to reinforcement parameters of the generalized matching law, as well as the percentage of the variance accounted for, decreased within the session. Negative sensitivity parameters were sometimes found late in the session for the concurrent food-water schedules. These results imply that within-session changes in responding could cause problems for assessing the validity of quantitative theories of concurrent-schedule responding when the components provide different reinforcers. They question changes in a general motivational state, such as arousal, as a complete explanation for within-session changes in responding. The results are compatible with satiation for, or sensitization-habituation to, the reinforcers as explanations.
Journal of the experimental analysis of behavior, 1996 · doi:10.1901/jeab.1996.66-369