THE RELATIONS AMONG MEASURES OF PERFORMANCE ON FIXED-INTERVAL SCHEDULES.
Curvature measures on FI schedules stick together, but response rate walks its own path.
01Research in Context
What this study did
GOLLUMIGLER (1964) watched rats and pigeons work on fixed-interval schedules. The team tracked many small numbers: pause time, run rate, and curve shape. They wanted to see which numbers move together and which do not.
What they found
All the shape numbers marched in step with each other. Response-rate numbers only partly matched the shape numbers. So, one family of measures can stand in for another, but rate is its own story.
How this fits with other research
Duncan et al. (1972) later used the same numbers in a two-part FI schedule. They showed that response rate follows reinforcer rate, not part length. The old link between shape and rate still held.
Timberlake et al. (1987) moved the idea to adult humans under a game-like FI. Break-and-run curves showed up fast, proving the 1964 animal rules travel to people.
Poppen (1972) added a twist: when humans also had a second schedule, pause length flipped. This looks like a clash, but the extra schedule, not the FI, drove the change.
Why it matters
When you graph a client’s FI data, you can swap curvature, pause, or run measures without losing signal. Do not trust rate alone; it may drift while shape stays flat. If you add a side task, expect the pause to shift—plan probes and stay flexible.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Pick one curvature index (pause/run ratio) and track it for a week—ignore rate if shape is stable.
02At a glance
03Original abstract
Quantitative measures of the performances of seven rats and two pigeons under FI schedules of reinforcement were obtained. For the rats (under FI 2 and FI 100 sec) the mean response rate and two measures of the temporal distribution of responses within the interval (quarter-life and an Index of Curvature) were computed for individual intervals. The measures of curvature were highly correlated with each other, whereas the response rate was only moderately correlated with either of them. Similar results were found for comparisons of the same measures on a session-by-session basis. The performances of the pigeons (under FI 10) were analyzed to yield response rate, quarter-life and elapsed time to the first, fifth and tenth response. Response rate was only moderately correlated with quarter-life, whereas quarter-life and time to the fifth or tenth response were highly correlated. Measures of temporal distribution based on an average of the intervals of a daily session were highly similar to the means of those measures calculated from the individual intervals.
Journal of the experimental analysis of behavior, 1964 · doi:10.1901/jeab.1964.7-337