Effects of step size and break-point criterion on progressive-ratio performance.
Progressive-ratio step size mainly reduces how many ratios animals attempt, not the final ratio they achieve, and a longer break-point criterion lets them do more work overall.
01Research in Context
What this study did
D and colleagues tested how step size changes progressive-ratio work. They used pigeons pecking for food. The ratio went up by 5, 10, 20, or 40 after each reinforcer.
They also tried two break-point rules. One stopped the session after 5 min with no response. The other waited 15 min.
What they found
Bigger steps did not lower the final ratio the birds reached. But birds finished fewer ratios and pecked slower when steps were large.
The longer 15-min break rule let birds do more total work. The final ratio stayed the same, they just kept trying longer.
How this fits with other research
Northup et al. (1991) saw an upside-down U when they changed food amount. D et al. kept food the same and changed step size. Both show ratio strain, just different knobs.
Clopton (1972) gave birds drugs that raised breakpoints. D et al. show you can raise total work without drugs by simply waiting longer. Same measure, cheaper method.
Gettinger (1993) split performance into pause time vs peck time. D et al. found step size hits peck speed, not breakpoint. Together they say: watch both parts, not just the top number.
Why it matters
When you shape a new skill, the size of each demand jump matters. Big jumps slow the client down but do not always drop the highest level they can reach. If you give more wait time after a pause, you may see extra trials without extra prompts. Try smaller steps when you want steady speed, and longer wait windows when you want to see how far the learner can really go.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Add a 15-min pause window to your next progressive-ratio probe and count if the learner starts another ratio after a long break.
02At a glance
03Original abstract
Key pecking by pigeons was maintained by arithmetic progressive-ratio schedules of food delivery. Successive conditions arranged different step sizes, and each condition remained in effect until behavior appeared stable. Each session continued until a period of time passed in which no key pecks were recorded (the break-point criterion); both a 5-min and a 15-min criterion were tested across a range of step sizes. Average breaking points (i.e, the largest ratio completed) were relatively unaffected by step-size magnitude, whereas the average number of ratios completed and average response rates generally declined across increasing step sizes. Within sessions, preratio pauses were relatively short and fairly constant in duration as the ratio increased; pause durations increased rapidly near the end of a session. The relation between the average number of completed ratios and step size was described well by a power function [y = b(xa), in which y represents the average number of completed ratios, x represents the step size, and a and b are fitted parameters]. Increasing the break-point criterion from 5 to 15 min resulted in increased values of b, whereas parameter a was relatively unaffected and was close to -1 (consistent with the lack of effect of step size on breaking point). This function also provided an excellent description of data drawn from previous reports.
Journal of the experimental analysis of behavior, 1998 · doi:10.1901/jeab.1998.70-123