Do the adjusting-delay and increasing-delay tasks measure the same construct

Abstract

Delay discounting describes the subjective devaluation of a reward when it is delayed. In animals, the adjusting- and increasing-delay tasks often are used to assess individual differences in, and drug effects on, delay discounting. No study to date, however, has compared systematically the measures of discounting produced in these tasks. The current study examined the correlation between measures of delay discounting derived from adjusting- and increasing-delay procedures. Twenty rats completed 30 sessions under each task (order counterbalanced across rats). Quantitative measures of delay discounting produced by the two tasks were positively correlated, suggesting that the adjusting-and increasing-delay tasks measure the same underlying facet of impulsive choice (i.e., individual or conjoint sensitivities to reward delay and magnitude). The measures derived from either task, however, depended on the sequences in which the tasks were experienced. That is, pre-exposure to one task decreased discounting of delayed rewards in the second task. Consistent with other published findings, exposure to delayed consequences during the initial discounting assessment might explain this effect. Despite the observed correlation between ID and AD indifference delays, we suggest that the ID procedure might be a more appropriate procedure for pharmacological studies.

Discrepant effects of acute cocaine on impulsive choice (delay discounting) in female rats during an increasing- and adjusting-delay procedure

“…1) suggests that both quantify the same underlying construct of impulsive choice in female rats. These findings extend a recent study by Craig et al (2014) who found the same positive correlation between these procedures, but in male rats. Indeed, related pigeon research has demonstrated that discounting rates determined via an adjusting-amount and -delay procedure were also positively correlated (Green et al 2007).…”

“…When combined, the present results suggest these impulsive choice procedures, each of which can assess the acute drug effects on impulsive choice in a single session, produce concordant measures of delay discounting rates in animals. As hypothesized by Craig et al (2014) and demonstrated in the present study, however, acute drug effects can produce conflicting results between these two choice procedures (see Stein and Madden 2013 for a review of issues).…”

“…Females were used in this initial study since it complements previous research by Craig et al (2014) that employed males, supports the NIH aim to expand use of females in research, and because female rats are more vulnerable to drug abuse (Anker and Carroll 2011). Upon arrival, rats were group housed in standard polycarbonate home-cages with ad libitum food and water access for a week.…”

“…An initial step to test this hypothesis is to determine if measures of discounting are related across the AD and ID procedures. Indeed, a very recent follow-up study by Craig et al (2014) showed that discounting rates in male rats were positively correlated between these procedures. The main purposes of the present study were to 1) extend the findings to female rats and determine whether discounting rates across the ID and AD procedures were related and 2) determine if acute doses of cocaine produce concordant changes in delay discounting within the ID and AD choice procedures.…”

Working‐memory training: Effects on delay discounting in male long evans rats

“…An additional 20 sessions were conducted following the correction of the programming error. Adjusting delays typically stabilize in 30 sessions or less (see, e.g., Craig, Maxfield, Stein, Renda, & Madden, 2014; Mazur, 2012) and have good test-retest reliability when assessed in a fixed number of sessions (McClure, Podos, & Richardson, 2014). Each rat's mean adjusted delay (MAD) over the final nine sessions served as the measure of delay discounting.…”