Intertrial interval duration and impulsive choice

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.

Time discounting and time preference in animals: A critical review

“…8C). The idea that animals suboptimally incorporate postreward delays into their strategies is supported by other studies, as well (Lea, 1979;Logue et al, 1985;Smethells & Reilly, 2014;Stephens & Dunlap, 2009). …”

Impulsivity or Sub-optimal Reward Maximization in Delay Discounting? A Critical Discussion

“…The inter-trial-interval appears to have minimal impact on choice if the delay between response and reward for LL is absent or short Smethells & Reilly, 2015). However, if the delay is long (approx.…”

“…However, if the delay is long (approx. six seconds or more), then short inter-trial-intervals results in impulsive choices, while long ones do not (Smethells & Reilly, 2015). This suggests that the delay and inter-trial-interval components interacts.…”

“…Food pellets (Fox et al, 2008) or water drops (Reynolds, De Wit, & Richards, 2002) are typically used for rats, with grain for pigeons (Mazur, 1987;Smethells & Reilly, 2015). In animal studies, the term used for consequences of behaviour that select, increase and control behaviour is usually reinforcer, which is a strictly behavioural term defined by its effect, and with no reference to subjective or cognitive states.…”

The role of temporal intervals on reinforcer accumulation

“…This ITI effect is consistent with Mazur (), who demonstrated that when ITI response requirements were added to a discrete‐trial choice procedure using rats, preferences for a larger–later reinforcer increased. Smethells and Reilly () further substantiated this finding using ITIs, but without the response requirement.…”