Behavioral contrast and relative reinforcement frequency in two multiple schedules.
FR schedules spark behavioral contrast, but boosting reinforcement or switching to low-rate schedules can stop the swing.
01Research in Context
What this study did
Pigeons pecked on two keys in a single-case lab setup.
Each session had two parts that alternated.
One part used a fixed-ratio (FR) schedule.
The other part used a low-rate schedule.
The team varied how often food followed correct pecks.
They watched for contrast: did peck speed in one part swing when the other part changed?
What they found
Contrast showed up only in the FR part.
When food odds dropped in the other part, FR pecking sped up.
Low-rate parts stayed steady.
Raising the food rate wiped out the contrast.
More food kept the birds calm and steady across parts.
How this fits with other research
Innis (1978) extends this work.
They also used multiple schedules but saw negative contrast under VI parts.
Their birds slowed down when the other part paid more.
The two studies look opposite, yet both say schedule type sets the direction of change.
Whalen et al. (1979) later clarified the math.
They told researchers to compare equal-baseline rates first.
This update helps explain why FR and VI give different contrast signs.
Pickering et al. (1985) used similar VI setups and found overmatching.
Their birds leaned even harder into the rich part than the pay rate said they should.
Together the papers show: richer parts pull extra work, but the shape of that pull depends on schedule and access time.
Why it matters
When you run mixed programs, watch the schedule type.
FR-like demands can spark contrast: the client may rush when another task pays less.
You can dampen this by raising the payoff or shifting to low-rate or VI shapes.
Check response speed across components; if you see swings, tweak rate before trying new reinforcers.
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Join Free →Track response rate in each part of your mixed program; if FR parts speed up when other parts thin, raise the FR payoff or swap to VI.
02At a glance
03Original abstract
After preliminary variable-interval training, one group of pigeons was trained on a series of multiple variable-interval low-rate reinforcement schedules, while another group was trained on a series of multiple variable-interval fixed-ratio reinforcement schedules. Contrast effects were observed as variable-interval baseline rate changed in a direction away from the change in reinforcement frequency in the other component. The effects of the variable-interval component on performance in the low-rate and fixed-ratio reinforcement components in the multiple schedules were assessed by comparing the birds' performances on each of these schedules alone. Fixed-ratio reinforcement schedules showed a susceptibility to contrast effects, low-rate reinforcement schedules did not. The rate of reinforcement in fixed-ratio schedules at which no interaction occurred in the multiple schedules was higher than that in variable-interval 1-min schedules, suggesting that pigeons may prefer time-based, rather than response-based, reinforcement.
Journal of the experimental analysis of behavior, 1967 · doi:10.1901/jeab.1967.10-151