An exploratory examination of delay discounting in women and girls diagnosed with an eating disorder.

Those with eating disorders (EDs) characterized by purging behaviors tend to show more impulsivity than those diagnosed with restrictive eating, who tend to show more compulsivity. Impulsive choice (i.e. a type of impulsivity) is a common factor among eating disorders that is less understood. Delay discounting is a measure of choice impulsivity, examining the decrease in value of delayed outcomes. In this exploratory study, we examined associations between eating disorder type, age and delay discounting among patients at a residential ED treatment center (N = 178). Our findings showed that those diagnosed with bulimia nervosa had higher delay discounting (i.e. more impulsivity) at intake compared to anorexia nervosa, binge eating disorder, and other eating types but there were no significant differences. Those diagnosed with bulimia nervosa, as well as those with ARFID and unspecified ED showed a preference for delayed rewards at discharge, but there were no significant differences among ED types. Moderation analyses showed that age, ED type, nor the interaction did not significantly predict delay discounting at intake or discharge. To conclude, those with bulimia nervosa demonstrate less impulsive choice at discharge from a residential ED treatment center. However, additional research is needed given the variability of sample sizes in this study.

An apparatus and procedure for studying discounting of real outcomes of money and aversive sound.

We developed and examined a laboratory preparation with adult humans that pits shorter term avoidance over longer term positive reinforcement and may serve as a useful laboratory functional analogue of problematic behavior. Participants were exposed to choices between (1) avoiding an aversive sound and acquiring no money or (2) listening to an aversive sound for a set duration and then receiving money. The first choice, avoiding an aversive sound and acquiring no money, was conceptualized as immediate negative reinforcement and no positive reinforcement, whereas the latter choice, listening to an aversive sound for a set duration and then receiving money, was conceptualized as a potential positive punisher paired with a larger later positive reinforcer. We manipulated the duration of the sound and the magnitude of money to identify the point at which individual participants' choices changed from avoiding the sound to choosing the sound plus money. As the sound duration increased, the choice of listening to the sound and receiving money decreased. Similar functions were observed with two different monetary magnitudes. The model has potential applicability to real-world problems such as smoking, addiction, gambling, anxiety disorders, and other impulse control disorders.

Temporal expectations in delay of gratification.

We examined how temporal expectations influence preference reversals in a delay of gratification task for rats based on a hypothesis of Rachlin (2000), who suggested that preference for a larger-later reward may shift in favor of a smaller-immediate reward as a result of changes in when that larger reward is expected. To explore Rachlin's hypothesis, we preexposed two groups of rats to the delays associated with a larger-later reinforcer from a delay of gratification task. One group experienced the delays as a function of their choices in an intertemporal choice task and the other group experienced delays yoked from the first group (independent of their behavior) in an exposure training procedure. In addition, we included a third group of rats that were not exposed to delays during preexposure training as a comparison to the other two groups. Overall, the two groups of rats that experienced delays during preexposure training tended to make fewer defection responses than the comparison group during the delay of gratification task. Consistent with Rachlin's hypothesis, our results suggest that temporal learning may influence preference reversals in a delay of gratification task, providing a number of future directions for research in this area.

Sooner is Better: Longitudinal Relations Between Delay Discounting, and Depression and Anxiety Symptoms among Vietnamese Adolescents.

Delay discounting refers to the decline in the present value of an outcome as a function of the delay to its receipt. Research on delay discounting initially focused on substance abuse, generally finding that greater delay discounting is associated with increased risk for and severity of substance abuse. More recently, delay discounting has been linked theoretically and empirically to affective psychopathology, potentially suggesting novel intervention targets for mental health problems such as depression and anxiety. Longitudinal research consequently is critical to determine direction of causality and rule out possible third variable explanations. Only a small number of longitudinal studies have been conducted in this area, however. Furthermore, socio-economic and socio-cultural factors may influence delay discounting and its effects, but thus far the literature is relatively limited in this regard. The present study focused on adolescence, a key time-period for development of delay discounting and emotional problems. Longitudinal relations between delay discounting, and depression and anxiety symptoms were assessed among 414 adolescents in Vietnam, a lower-middle-income Southeast Asian nation with significant cultural divergence from Western countries. In contrast to most cross-sectional studies that have found positive or non-significant correlations, in the present study delay discounting at Time 1 had a negative beta with anxiety and depression symptoms at Time 1, with preference for immediate but smaller rewards (higher discounting) at Time 1 associated with lower anxiety and depression symptoms at Time 2. These results suggest that under certain circumstances, steeper delay discounting may be adaptive and supportive of emotional mental health.

Reinforced behavioral variability in the valproate rat model of autism spectrum disorder.

Individuals diagnosed with autism spectrum disorder (ASD) tend to display restricted, repetitive behaviors and deficits in social interaction. Rats exposed to valproate (VPA) in utero have been shown to model symptoms of ASD. In previous research, VPA rats engaged in less social interaction and more repetitive responding than controls. The purpose of the present study was to further investigate behavioral variability in the VPA rat model of ASD by testing VPA and control rats in a reinforced-behavioral-variability operant task. In this procedure, rats emitted sequences of lever presses, some of which produced food. During baseline, food was delivered probabilistically, and variability was not required. Next, rats were exposed either to a variability contingency, in which food was only delivered following sequences that differed sufficiently from previous sequences (i.e., variability required), or to a yoked contingency, in which variability was not required. We hypothesized that VPA rats would behave less variably than controls in this task. However, VPA and control rats responded similarly variably when variability was required. Furthermore, VPA rats behaved slightly more variably than controls during baseline and yoked conditions, when variability was not required. These findings contribute to the complex literature surrounding the VPA rat model of ASD.

Testing delay of gratification in rats using a within-session increasing-delay task.

In delay discounting, preference reversals refer to shifts in preference from a larger-later reward to a smaller-sooner reward. Steep hyperbolic discounting predicts a preference reversal when a smaller-sooner and larger-later reward both become temporally proximal; prior research is consistent with this prediction. Hyperbolic discounting does not predict a preference reversal, however, after an individual chooses a larger-later reward over a smaller-immediate reward; prior research is inconsistent with this prediction. We sought to replicate and extend these findings using a delay of gratification task in rats. The task included a defection response which allowed rats to reverse their preference after choosing a larger-later sucrose reinforcer to instead obtain a smaller-immediate sucrose reinforcer. In Experiment 1, we found that rats would defect on their choice of the larger-later reinforcer, systematically replicating prior research. We also found that experience on the delay of gratification task led to decreases in defection responses. In Experiment 2, we found that prior experience on an intertemporal choice task, with no opportunity to defect, also led to few defection responses on the delay of gratification task. We discuss our findings in the context of whether inhibitory control or temporal learning could be involved in delay of gratification.

Deprivation Has Inconsistent Effects on Delay Discounting: A Review.

Delay discounting, the tendency for outcomes to be devalued as they are more temporally remote, has implications as a target for behavioral interventions. Because of these implications, it is important to understand how different states individuals may face, such as deprivation, influence the degree of delay discounting. Both dual systems models and state-trait views of delay discounting assume that deprivation may result in steeper delay discounting. Despite early inconsistencies and mixed results, researchers have sometimes asserted that deprivation increases delay discounting, with few qualifications. The aim of this review was to determine what empirical effect, if any, deprivation has on delay discounting. We considered many kinds of deprivation, such as deprivation from sleep, drugs, and food in humans and non-human animals. For 23 studies, we analyzed the effect of deprivation on delay discounting by computing effect sizes for the difference between delay discounting in a control, or baseline, condition and delay discounting in a deprived state. We discuss these 23 studies and other relevant studies found in our search in a narrative review. Overall, we found mixed effects of deprivation on delay discounting. The effect may depend on what type of deprivation participants faced. Effect sizes for deprivation types ranged from small for sleep deprivation (Hedge's gs between -0.21 and 0.07) to large for opiate deprivation (Hedge's gs between 0.42 and 1.72). We discuss possible reasons why the effect of deprivation on delay discounting may depend on deprivation type, including the use of imagined manipulations and deprivation intensity. The inconsistency in results across studies, even when comparing within the same type of deprivation, indicates that more experiments are needed to reach a consensus on the effects of deprivation on delay discounting. A basic understanding of how states affect delay discounting may inform translational efforts.

Discounting of food and water in rats shows trait- and state-like characteristics.

Delay discounting is the loss in value of an outcome as a function of its delay. The present study focused on examining a trait-like characteristic of delay discounting in a preclinical animal model. Specifically, we were interested in whether there was a positive relation between discounting of 2 different outcomes in rats. That is, would rats that discount delayed food steeply also discount delayed water steeply? In addition, we examined how session-to-session variability in discounting could be attributed to differences between subjects (trait variability) and to differences within subjects (state variability). Finally, we measured discounting from early- to mid-adulthood, allowing us to examine changes in discounting as a function of age. Overall, we found a moderate, positive correlation between discounting of food and discounting of water in rats, providing further evidence that the relative consistency with which individuals discount different outcomes is a trait-like characteristic. In addition, we found a high degree of within-subject variability in discounting, indicating strong state-like differences from session to session. Finally, overall, discounting decreased as a function of age; however, individual-subject data showed variability in how discounting changed across time. Overall, our results show that differences in delay discounting between individuals reflect variability in both trait- and state-like characteristics.

An investigation of resurgence of reinforced behavioral variability in humans.

The present study examined resurgence of reinforced variability in college students, who completed a 3-phase computer-based variability task. In the first phase, baseline, points were delivered for drawing rectangles that sufficiently differed from previous rectangles in terms of a target dimension (size or location, counterbalanced) but were sufficiently similar in terms of the alternative dimension. In the second phase, alternative, points were only delivered for rectangles that were sufficiently different in terms of the alternative dimension, but repetitive in terms of the target dimension. In the third phase, extinction, no points were delivered. In baseline, participants made rectangles that were highly varied in terms of the target dimension and less varied in terms of the alternative dimension, and vice versa in the alternative phase. During extinction, levels of variability increased for the target dimension, providing evidence for resurgence of reinforced variability of a specific dimension of behavior. However, levels of variability also remained high for the alternative dimension, indicating that extinction-induced response variability may also have impacted the results. Although future research is needed to explore other explanations, the results of this study replicate prior research with pigeons and provide some support for the notion of variability as an operant.

Comparison of delay discounting of different outcomes in cigarette smokers, smokeless tobacco users, e-cigarette users, and non-tobacco users.

Delay discounting is the process by which a commodity loses value as the delay to its receipt increases. Rapid discounting predicts various maladaptive behaviors including tobacco use. Typically, delay discounting of different outcomes has been compared between cigarette smokers and nonsmokers. To better understand the relationship of delay discounting to different modes of tobacco use, we examined the differences in delay discounting of different outcomes between cigarette smokers, smokeless tobacco users, e-cigarette users, and non-tobacco users. In the present study, all participants completed 8 titrating delay-discounting tasks: $100 gain, $500 gain, $500 loss, alcohol, entertainment, food, a temporary health gain, and a temporary cure from a disease. Non-tobacco users discounted most outcomes less than tobacco users overall; however, there were no differences in discounting among the different types of tobacco users. These results suggest that nicotine consumption of any kind is associated with a higher degree of impulsivity compared to non-tobacco users. Adoption of tobacco products that have been perceived as less harmful (e.g., e-cigarettes) is not associated with a baseline difference or decrease in delay discounting if adopted after a history of cigarette use.

Choice for reinforced behavioral variability in children with autism spectrum disorder.

Although individuals with autism spectrum disorder (ASD) tend to behave repetitively, certain reinforcement contingencies (e.g., lag schedules) can be used to increase behavioral variability. In a lag schedule, reinforcers only follow responses that differ from recent responses. The present study was designed to promote variable play behavior in preschoolers with ASD interacting with playsets and figurines and to assess preference for variability and repetition contingencies. Data have shown a preference for variability in pigeons and college students, but this effect has not been explored in clinical populations. In this experiment, preschoolers with ASD were taught to discriminate between variability and repetition contingencies. Only play behaviors that met a lag schedule were reinforced in the presence of one color, and only repetitive behaviors were reinforced in the presence of another. After differential performance was established, participants experienced a concurrent chains schedule. Participants chose between the colors taught in training and then completed a play session with the selected contingency. One participant selected variability and repetition equally. The other participants showed a slight preference for variability. These results indicate that some individuals with ASD may play repetitively, not because they prefer repetition, but because they require additional teaching to play variably.

Delay discounting of different outcomes: Review and theory.

Steep delay discounting is characterized by a preference for small immediate outcomes relative to larger delayed outcomes and is predictive of drug abuse, risky sexual behaviors, and other maladaptive behaviors. Nancy M. Petry was a pioneer in delay discounting research who demonstrated that people discount delayed monetary gains less steeply than they discount substances with abuse liability. Subsequent research found steep discounting for not only drugs, but other nonmonetary outcomes such as food, sex, and health. In this systematic review, we evaluate the hypotheses proposed to explain differences in discounting as a function of the type of outcome and explore the trait- and state-like nature of delay discounting. We found overwhelming evidence for the state-like quality of delay discounting: Consistent with Petry and others' work, nonmonetary outcomes are discounted more steeply than monetary outcomes. We propose two hypotheses that together may account for this effect: Decreasing Future Preference and Decreasing Future Worth. We also found clear evidence that delay discounting has trait-like qualities: People who steeply discount monetary outcomes steeply discount nonmonetary outcomes as well. The implication is that changing delay discounting for one outcome could change discounting for other outcomes.

Evaluating the effect of delay spacing on delay discounting: carry-over effects on steepness and the form of the discounting function.

Most delay discounting studies use tasks that arrange delay progressions in which the spacing between consecutive delays becomes progressively larger. To date, little research has examined delay discounting using other progressions. The present study assessed whether the form or steepness of discounting varied across different delay progressions. Human participants completed three discounting tasks with delay progressions that varied in the time between consecutive delays: a standard (increasing duration between delays), linear (equal duration between delays), and an inverse progression (decreasing duration between delays). Steepness of discounting was generally reduced, and remained so, following experience with the inverse progression. Effects of the delay progression on the best fitting equation were order-dependent. Overall the hyperbola model provided better fits, but the exponential model performed better with data from the inverse progression. Regardless, differences in which model fit best were often small. The finding that the best fitting model was dependent, in some cases, on the delay progression suggests that a single quantitative model of discounting may not be applicable to describe discounting across all procedural contexts. Ultimately, changes in steepness of discounting following experience with the inverse progression appeared similar to anchoring effects, whose mechanism will require further study to delineate.

Obsessive-Compulsive Symptoms Are Associated With Increased Delay Discounting in a Novel Hand-Washing Task.

Delay discounting is a theoretical framework for assessing impulsivity characterized by a tendency to choose SSRs over LLRs. Despite the potential therapeutic value of targeting impulsive choice in the context of obsessive-compulsive (OC) symptoms, little research has been done to examine the link between the 2. In the present study, we examined the role of impulsivity in OC symptoms using a monetary and novel hand-washing delay-discounting task. Participants completed both delay-discounting procedures, as well as the Obsessive-Compulsive Inventory-Revised (OCI-R; Foa et al.,2002). Participants who showed steeper delay discounting in the monetary discounting task also tended to discount steeply in the washing task. In addition, participants showed significantly more delay discounting in the washing than in the monetary task, suggesting contextual control over impulsive behavior. Further, participants with washing compulsions demonstrated greater delay discounting on the washing task than those without washing compulsions. Higher scores on the Washing subscale of the OCI-R uniquely predicted delay discounting in the washing task at a level of marginal significance. Our findings suggest that impulsivity may be implicated in OC symptoms, and indicate the need for a more precise conceptualization of the relationship between impulsivity and compulsivity.

The effect of nicotine and nicotine+monoamine oxidase inhibitor on the value of alcohol.

Alcohol is the most commonly abused drug in the USA and many people suffer from alcohol use disorder. Many factors are associated with alcohol use disorder, but the causal role of comorbid nicotine use has not been extensively considered. Nicotine has reward-enhancing properties and may increase the value of alcohol. Monoamine oxidase inhibition increases nicotine self-administration and may increase the reward-enhancing effects of nicotine. We assessed the effect of nicotine and nicotine in combination with a commonly used monoamine oxidase inhibitor (tranylcypromine) on the value of alcohol using a progressive ratio schedule of reinforcement in rats. Nicotine administration increased the breakpoint for alcohol, but nicotine in combination with tranylcypromine decreased the breakpoint for alcohol. The current study adds to previous research showing that nicotine increases the value of alcohol. This finding has important implications for the etiology of addiction because of the comorbidity of smoking with many drugs of abuse. The finding that nicotine in combination with tranylcypromine reduces the value of alcohol warrants further investigation.

An alternative approach to relapse analysis: Using Monte Carlo methods and proportional rates of response.

Relapse is the recovery of a previously suppressed response. Animal models have been useful in examining the mechanisms underlying relapse (e.g., reinstatement, renewal, reacquisition, resurgence). However, there are several challenges to analyzing relapse data using traditional approaches. For example, null hypothesis significance testing is commonly used to determine whether relapse has occurred. However, this method requires several a priori assumptions about the data, as well as a large sample size for between-subjects comparisons or repeated testing for within-subjects comparisons. Monte Carlo methods may represent an improved analytic technique, because these methods require no prior assumptions, permit smaller sample sizes, and can be tailored to account for all of the data from an experiment instead of some limited set. In the present study, we conducted reanalyses of three studies of relapse (Berry, Sweeney, & Odum, ; Galizio et al., ; Odum & Shahan, ) using Monte Carlo techniques to determine if relapse occurred and if there were differences in rate of response based on relevant independent variables (such as group membership or schedule of reinforcement). These reanalyses supported the previous findings. Finally, we provide general recommendations for using Monte Carlo methods in studies of relapse.

The effects of outcome unit framing on delay discounting.

We examined the effects of outcome framing on delay discounting. In Experiment 1, participants completed four delay-discounting tasks. In one monetary task, money was framed in units of dollars (＄50), and in the other, money was framed in units of handfuls of quarters (equal to ＄50). In one food task, food was framed in clear units of food (e.g., 100 M&Ms), and in the other, food was framed in units of servings (e.g., 10 servings of M&Ms). When money was framed in units of dollars, participants discounted less by delay compared to discounting of handfuls of quarters. When food was framed as clear units, participants also discounted less compared to how they discounted servings. In Experiment 2, participants completed two delay-discounting tasks for dollars and quarters (e.g., ＄50 or 200 quarters) to determine if the results of Experiment 1 were due to the differences in handling costs. In one delay-discounting task, money was framed in units of dollars. In the other delay-discounting task, money was framed in units of quarters. There was no difference in how participants discounted delayed money framed as dollars or quarters. Clear unit framing may result in less discounting by delay than fuzzy unit framing.

Continuous nicotine exposure does not affect resurgence of alcohol seeking in rats.

Alcohol is the most commonly used drug in the United States and alcohol abuse can lead to alcohol use disorder. Alcohol use disorder is a persistent condition and relapse rates following successful remission are high. Many factors have been associated with relapse for alcohol use disorder, but identification of these factors has not been well translated into preventative utility. One potentially important factor, concurrent nicotine use, has not been well investigated as a causal factor in relapse for alcohol use disorder. Nicotine increases the value of other stimuli in the environment and may increase the value of alcohol. If nicotine increases the value of alcohol, then nicotine use during and after treatment may make relapse more probable. In the current study, we investigated the effect of continuous nicotine exposure (using osmotic minipumps to deliver nicotine or saline, depending on group, at a constant rate for 28 days) on resurgence of alcohol seeking in rats. Resurgence is a type of relapse preparation that consists of three phases: Baseline, Alternative Reinforcement, and Resurgence Testing. During Baseline, target responses produced a dipper of alcohol. During Alternative Reinforcement, target responses were extinguished and responses on a chain produced a chocolate pellet. During Resurgence Testing, responses on the chain were also extinguished and a return to responding on the target lever was indicative of resurgence. Multilevel modeling was used to analyze the effect of nicotine on resurgence. Both the nicotine and saline group showed resurgence of alcohol seeking, but there was no difference in the degree of resurgence across groups. Future directions could involve testing alternative drug delivery techniques.

Persistence and relapse of reinforced behavioral variability.

The present study examined persistence and relapse of reinforced behavioral variability in pigeons. Pigeons emitted four-response sequences across two keys. Sequences produced food according to a lag schedule, in which a response sequence was followed by food if it differed from a certain number of previous sequences. In Experiment 1, food was delivered for sequences that satisfied a lag schedule in both components of a multiple schedule. When reinforcement was removed for one component (i.e., extinction), levels of behavioral variability decreased for only that component. In Experiment 2, food was delivered for sequences satisfying a lag schedule in one component of a multiple schedule. In the other component, food was delivered at the same rate, but without the lag variability requirement (i.e., yoked). Following extinction, levels of behavioral variability returned to baseline for both components after response-independent food delivery (i.e., reinstatement). In Experiment 3, one group of pigeons responded on a lag variability schedule, and the other group responded on a lag repetition schedule. For both groups, levels of behavioral variability increased when alternative reinforcement was suspended (i.e., resurgence). In each experiment, we observed some evidence for extinction-induced response variability and for variability as an operant dimension of behavior.