Schedule-induced polydipsia: are response-dependent schedules a limiting condition?
Adjunctive drinking grows with the minutes between food, not with accidental rewards for pressing.
01Research in Context
What this study did
The team gave rats food on two kinds of schedules. One schedule required a lever press for each pellet. The other gave pellets for free at set times.
They made the wait between pellets longer and longer. Then they measured how much water the rats drank right after each pellet.
The goal was to see if the drinking was caused by the wait itself, or by accidental reinforcement of the lever press.
What they found
Longer waits always produced more post-pellet drinking. It did not matter if the rat had to press a lever or just wait.
This means the drinking scales with interval length, not with accidental reward for pressing.
How this fits with other research
Falk (1966) saw the same linear climb in drinking when only the fixed-interval length changed. The new study adds lever-press and free-pellet conditions to prove the rule.
Nelson et al. (1978) later doubled the effect by stretching the interval from 15 s to 60 s. Again, most drinks came right after the pellet, backing up the interval story.
Baer (1974) went further and showed the drinking appears any time water is there during spaced feeding. Together, the four papers lock in the idea that time between food, not the response rule, drives adjunctive behavior.
Why it matters
When you see a client drink, pace, or bite nails between reinforcers, think interval first. Lengthening the schedule may boost these interim acts even if no response is required. You can plan shorter intervals, offer alternate activities, or withhold the water cup during waits to keep adjunctive behavior in check.
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Try cutting the inter-reinforcer time in half and note if post-reward drinking or stereotypy drops.
02At a glance
03Original abstract
The collateral water intake of albino rats was measured when the inter-pellet intervals in fixed-ratio and fixed-time schedules were equated. Fixed-ratio and fixed-time inter-pellet intervals were equated by dividing the average fixed-ratio session time of each subject by 150 (food pellets). The average inter-pellet interval obtained then defined the subsequent fixed-time schedule for each individual subject. Shifts to fixed-time schedules followed the completion of each fixed-ratio 20, 40, and 80 schedule. This procedure permitted an assessment of the extent to which excessive collateral drinking was associated with inter-pellet interval length or adventitious food reinforcement. For both the fixed-ratio and fixed-time schedules, drinking progressively increased as a function of increasing the duration of the inter-pellet interval and was a post-pellet event under the control of variables other than adventitious food reinforcement.
Journal of the experimental analysis of behavior, 1970 · doi:10.1901/jeab.1970.13-351