Intertrial interval duration and impulsive choice.
Short intertrial intervals push animals and humans toward impulsive choices, so keep ITIs long during self-control assessments.
01Research in Context
What this study did
Cox et al. (2015) tested how long the pause between trials affects choices. They used rats and pigeons in a self-control game. The animals picked between a small treat now or a bigger treat later.
Each session had many trials. The researchers changed only the intertrial interval (ITI). Some sessions had short 5-second pauses. Others had longer 15- or 30-second pauses.
What they found
Short pauses made the animals more impulsive. They took the small immediate reward more often. Long pauses helped them wait for the bigger reward.
The effect showed up every time they tested. A 5-second ITI created the most impulsive choices. A 30-second ITI created the least.
How this fits with other research
Sanford et al. (1980) seems to say the opposite. They found autistic children learn faster with short 1-second pauses, not long ones. The two studies disagree because they measure different things. R et al. looked at impulsive choice in animals. L et al. looked at skill learning in children. Short ITIs hurt patience but help acquisition.
Cariveau et al. (2016) later confirmed the child data. They also saw faster tact and intraverbal mastery with 2-second ITIs in DTT. The animal and human lines both hold. They just apply to different goals.
Austin et al. (2015) showed timing gets sloppy when the participant starts the clock. Together these papers say: keep ITIs long for self-control tasks, short for teaching tasks, and add clear signals when precision matters.
Why it matters
When you run delay-discounting or self-control programs, stretch the ITI to at least 15 seconds. Short pauses will inflate impulsive responding and underestimate the learner's real self-control. Save the quick 1-2 second ITIs for acquisition drills where speed helps, not for choice tasks where patience is the target.
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02At a glance
03Original abstract
Discrete-trial intertemporal choice procedures assess impulsive choice or preference for a smaller, immediate reinforcer over a larger, delayed one. The effect of the delay associated with the larger reinforcer has been the focus of much research. It, however, is not the only delay in the context of discrete-trial procedures. Often separating each choice trial is an intertrial interval (ITI) that maintains equal trial spacing of the two alternatives. The removal of this ITI has been shown to increase impulsive choice, perhaps because choosing the small alternative results in another choice trial immediately following reinforcer delivery. Impulsive choice has not been affected when the ITI duration is manipulated in conditions that equate the trial presentation rate across the two alternatives. These null results could have been due to floor effects and/or an inadequate range of ITI durations. To address these possibilities, three experiments were conducted to determine how changes in ITI duration affected impulsive choice in rats and pigeons. All three experiments found that preference for the large delayed alternative decreased (i.e., impulsive choice increased) when the ITI was shortened. Satiation was not a likely explanation since preference for the large alternative at the 0-s delay was not affected by ITI duration. Trial spacing, like other temporal properties of choice situations, is an important variable underlying the occurrence of impulsive choice.
Journal of the experimental analysis of behavior, 2015 · doi:10.1002/jeab.131