Choice for aperiodic versus periodic ratio schedules: A comparison of concurrent and concurrent-chain procedures.
The same pay schedules can look best or worst depending on how you let the learner choose.
01Research in Context
What this study did
The team gave rats two levers. One lever paid off on a fixed-ratio schedule. The other paid on a mixed schedule that changed unpredictably.
They tested the same rats two ways. First, both options were always available. Second, the rats had to pick one option before they could work for either payoff.
What they found
Seven of eight rats showed clear choice patterns. The surprise: their favorite schedule flipped when the procedure changed.
With both levers live, rats liked the fixed-ratio side. When they had to choose in two steps, they switched and preferred the mixed schedule.
How this fits with other research
Tracey et al. (1974) saw the same flip between simple concurrent and two-step arrangements. Their work warns that component length can fake matching.
Davison et al. (1989) later mapped how pay rates move response rates inside chain schedules. They confirm that adding a choice link changes the whole picture.
McLean et al. (2018) show choice drifts across days even when pay stays the same. Together these papers say: procedure details, not just pay, steer preference.
Why it matters
Your assessment format can reverse what looks like a client’s preference. A simple concurrent test might say "fixed-ratio wins," while a chain test says the opposite. Before you lock in a treatment, run both formats or pick the one that matches the natural environment. One quick switch can save weeks of poor progress.
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02At a glance
03Original abstract
Choice between mixed-ratio schedules, consisting of equiprobable ratios of 1 and 99 responses per reinforcement, and fixed-ratio schedules of food reinforcement was assessed by two commonly used procedures: concurrent schedules and concurrent-chains schedules. Rats were trained under concurrent fixed-ratio mixed-ratio schedules, in which both ratio schedules were simultaneously available, and under a concurrent-chains schedule, in which access to one of the mutually exclusive ratio schedules comprising the terminal links was contingent on a single "choice" response. The distribution of responses between the two ratio schedules was taken as the choice proportion under the concurrent procedure, and the distribution of "choice" responses was taken as the choice proportion under the concurrent-chains procedure. Seven of eight rats displayed systematic choice; of those, each displayed nearly exclusive choice for fixed-ratio 35 to the mixed-ratio schedule under the concurrent procedure, but each displayed nearly exclusive choice for the mixed-ratio schedule to fixed-ratio 35 under the concurrent-chains procedure. Thus, preference for a fixed or a mixed schedule of reinforcement depended on the procedure used to assess preference.
Journal of the experimental analysis of behavior, 1983 · doi:10.1901/jeab.1983.40-225