Some Effects Of Intertrial Interval Duration On Discrete-trial Choice.
Longer breaks between trials can wipe out preference unless the schedules are linked.
01Research in Context
What this study did
The team ran discrete-trial choice sessions. Two buttons delivered snacks on their own VI clocks.
They stretched the pause between trials. Some runs had short ITIs, others had long ITIs.
They also tested two link types. In one, both clocks kept ticking no matter what. In the other, only the chosen clock ran.
What they found
Long pauses washed out preference. Birds pecked each side about equally when ITIs grew.
This only happened with the unlinked clocks. When the clocks were linked, choice stayed biased toward the richer side.
Switch patterns did not fit a local-only rule. Birds were using more than just the last few seconds of data.
How this fits with other research
Tavassoli et al. (2012) stretched ITIs in a preschool social-skills program. Longer pauses helped kids learn and use the skills with new people. Their result seems opposite, but the goal was acquisition, not preference.
Macdonald et al. (1973) showed pigeons need any non-zero ITI to master matching-to-sample. Together the three papers say: ITI length can either help learning or flatten choice, depending on what you ask the subject to do.
Wilkinson et al. (1998) saw flat, non-exclusive choice under concurrent VI-EXT. Webb et al. (1999) saw the same flat line, but they caused it by stretching ITI instead of adding extinction. Both warn us that “no preference” can hide in different designs.
Why it matters
If you run concurrent schedules in a lab or a classroom, watch the ITI. A long wait can erase the very preference you want to study or teach. When you need clear bias, keep ITIs brief or use linked schedules. When you want balanced responding, build in longer pauses.
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02At a glance
03Original abstract
Pigeons were trained in Experiment 1 on a discrete‐trial concurrent variable‐interval (VI) 1‐min VI 3‐min schedule, and in Experiment 2 on a discrete‐trial concurrent VI 1.5‐min VI 1.5‐min schedule. In each experiment, the intertrial‐interval durations (ITIs) were 0 s, 6 s, 22 s, and 120 s, and the schedules were both independent and interdependent. The purpose of the research was to determine whether lengthening the ITI would disrupt any local control that existed, measured with respect to relative response rate and changeover probability. In Experiment 1, with the independent schedules, both preference and obtained relative reinforcement rate approximated .75 at short ITIs, but then decreased toward .50 with longer ITIs. With interdependent schedules, both preference and obtained relative reinforcement rate approximated .75 at all ITIs. In both experiments, with both independent and interdependent schedules, changeover probabilities for each response in a sequence of up to five successive responses to a given schedule were variable for individual birds. The average changeover probabilities for all birds suggested perseveration rather than a systematic increase within a given ITI or a systematic trend toward chance responding as ITI duration increased. Finally, the changeover functions did not differ when a sequence of responses was calculated to begin anew after reinforcement rather than with the first response on a schedule. Taken together, the data were inconsistent with a theory holding that only local processes underlie choice in discrete‐trial procedures.
Journal of the experimental analysis of behavior, 1999 · doi:10.1901/jeab.1999.71-375