Concurrent ratio schedules: Fixed vs. variable response requirements.
When payoff rates differ a lot, learners quickly stick to the richer schedule.
01Research in Context
What this study did
Hawkins (1979) set up two levers side-by-side.
Pressing on the left always took the same number of responses to earn food.
Pressing on the right took a changing number of responses.
The researcher slowly made the fixed side harder and watched which lever the animal chose.
What they found
At first the animal switched between the two levers.
When the fixed lever needed many more responses, the animal stopped switching.
It stayed on the richer side almost all the time.
Big differences in payoff speed locked the animal to one lever.
How this fits with other research
Burgess et al. (1971) ran a similar two-lever study eight years earlier.
They counted how often animals changed sides, not final choice.
Their data on changeovers set the stage for P’s focus on exclusive staying.
Van Houten et al. (1980) moved the same FR vs VR question into a classroom.
Deaf students earned tokens on either schedule.
VR tokens kept the kids more on-task and less disruptive.
The lab finding held: variable pay keeps behavior steadier.
Bell et al. (2017) swapped the fixed side for a variable-time schedule.
Pigeons still spent most time on the richer option.
The choice rule is general: wherever reinforcement is denser, behavior piles in.
Why it matters
When you set up concurrent tasks, watch the payoff rates.
If one task delivers reinforcement much faster, the learner will drop the other task.
Thin schedules carefully or add response help to keep both behaviors alive.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Check the reinforcement rate on each concurrent task; rebalance if one side is winning by a large margin.
02At a glance
03Original abstract
Rats were trained on concurrent fixed-ratio variable-ratio or concurrent fixed-ratio mixed-ratio schedules of food reinforcement. The variable-ratio schedule was composed of an arithmetic sequence of 11 ratios that averaged 50; the mixed-ratio schedule consisted of equiprobable ratios of 1 and 99. Fixed-ratio values, varied over experimental conditions, included 25, 35, 50, 60, and 99. The proportion of responses and time allocated to the variable- or mixed-ratio schedule increased as the size of the fixed ratio increased. For most subjects, higher proportions of responses and time were maintained on the fixed-ratio schedule at fixed-ratio values of 25 and 35; higher proportions of responses and time were maintained on the variable- or mixed-ratio schedule at fixed-ratio values of 50 or higher. On concurrent variable-ratio fixed-ratio schedules, the tendency for responding to be maintained exclusively by one schedule was related to the difference in local reinforcement rates obtained from those schedules. Exclusive responding was approximated when the difference in local reinforcement rates obtained from those schedules was large; responding was more evenly distributed between the schedules as the difference in the rates at which reinforcement was obtained from each decreased.
Journal of the experimental analysis of behavior, 1979 · doi:10.1901/jeab.1979.31-225