Brady Reynolds

Delay discounting and probability discounting as related to cigarette smoking status in adults.

This study examined relations between adult smokers and non-smokers and the devaluation of monetary rewards as a function of delay (delay discounting, DD) or probability (probability discounting, PD). The extent to which individuals discount value, either as a function of a reward being delayed or probabilistic, has been taken to reflect individual differences in impulsivity. Those who discount most are considered most impulsive. Previous research has shown that adult smokers discount the value of delayed rewards more than adult non-smokers. However, in the one published study that examined probability discounting in adult smokers and non-smokers, the smokers did not discount the value of probabilistic rewards more than the non-smoker controls. From this past research, it was hypothesized that measures of delay discounting would differentiate between smokers and non-smokers but that probability discounting would not. Participants were 54 (25 female) adult smokers (n = 25) and non-smokers (n = 29). The smokers all reported smoking at least 20 cigarettes per day, and the non-smokers reported having never smoked. The results indicated that the smokers discounted significantly more than the non-smokers by both delay and probability. Unlike past findings, these results suggest that both delay and probability discounting are related to adult cigarette smoking; however, it also was determined that DD was a significantly stronger predictor of smoking than PD.

Temporal and probabilistic discounting of rewards in children and adolescents: Effects of age and ADHD symptoms

This study investigated whether age and ADHD symptoms affected choice preferences in children and adolescents when they chose between (1) small immediate rewards and larger delayed rewards and (2) small certain rewards and larger probabilistic uncertain rewards. A temporal discounting (TD) task and a probabilistic discounting (PD) task were used to measure the degree to which the subjective value of a large reward decreased as one had to wait longer for it (TD), and as the probability of obtaining it decreased (PD). Rewards used were small amounts of money. In the TD task, the large reward (10 cents) was delayed by between 0 and 30s, and the immediate reward varied in magnitude (0-10 cents). In the PD task, receipt of the large reward (10 cents) varied in likelihood, with probabilities of 0, 0.25, 0.5, 0.75, and 1.0 used, and the certain reward varied in magnitude (0-10 cents). Age and diagnostic group did not affect the degree of PD of rewards: All participants made choices so that total gains were maximized. As predicted, young children, aged 6-11 years (n = 25) demonstrated steeper TD of rewards than adolescents, aged 12-17 years (n = 21). This effect remained significant even when choosing the immediate reward did not shorten overall task duration. This, together with the lack of interaction between TD task version and age, suggests that steeper discounting in young children is driven by reward immediacy and not by delay aversion. Contrary to our predictions, participants with ADHD (n = 22) did not demonstrate steeper TD of rewards than controls (n = 24). These results raise the possibility that strong preferences for small immediate rewards in ADHD, as found in previous research, depend on factors such as total maximum gain and the use of fixed versus varied delay durations. The decrease in TD as observed in adolescents compared to children may be related to developmental changes in the (dorsolateral) prefrontal cortex. Future research needs to investigate these possibilities.

Measuring state changes in human delay discounting: an experiential discounting task

A new experiential discounting task (EDT) is presented. Unlike existing question-based measures of delay discounting, which rely on imagined consequences during task completion, this EDT requires that participants experience choice consequences (i.e. delays and pseudo consumatory responses) during the measurement period. As a preliminary examination of this tasks sensitivity to variability in discounting, 12 participants (six females) completed a timing test (production and reproduction), a question-based measure of delay discounting, and the EDT during non-sleep-deprived (awake 7 h) and sleep-deprived (awake 21 h) conditions. Based on evidence that sleep deprivation increases impulsive behavior, it was hypothesized that participants would underrepresent time intervals in both production and reproduction procedures and discount significantly more with the discounting procedures while sleep deprived. Unfortunately, data from the question-based discounting procedure could not be reported due to invalid task completion. However, as hypothesized, certain production and reproduction intervals were underrepresented on the timing test, and discounting was significantly steeper on the EDT when participants were sleep deprived. Also, rate of discounting on the EDT was better characterized by a hyperbolic function than by exponential function, which is consistent with previous delay-discounting research. These preliminary results suggest this EDT may be a useful measure for assessing state changes in discounting processes.

Impulsive choice and response in dopamine agonist-related impulse control behaviors

RationaleDopaminergic medication-related impulse control disorders (ICDs) such as pathological gambling and compulsive shopping have been reported in Parkinson’s disease (PD).HypothesisWe hypothesized that dopamine agonists (DAs) would be associated with greater impulsive choice or greater discounting of delayed rewards in PD patients with ICDs (PDI).MethodsFourteen PDI patients, 14 PD controls without ICDs, and 16 medication-free matched normal controls were tested on the Experiential Discounting Task (EDT), a feedback-based intertemporal choice task, spatial working memory, and attentional set shifting. The EDT was used to assess choice impulsivity (hyperbolic K value), reaction time (RT), and decision conflict RT (the RT difference between high conflict and low conflict choices). PDI patients and PD controls were tested on and off DA.ResultsOn the EDT, there was a group by medication interaction effect [F(1,26) = 5.62; p = 0.03] with pairwise analyses demonstrating that DA status was associated with increased impulsive choice in PDI patients (p = 0.02) but not in PD controls (p = 0.37). PDI patients also had faster RT compared to PD controls [F(1,26) = 7.51, p = 0.01]. DA status was associated with shorter RT [F(3,24) = 8.39, p = 0.001] and decision conflict RT [F(1,26) = 6.16, p = 0.02] in PDI patients but not in PD controls. There were no correlations between different measures of impulsivity. PDI patients on DA had greater spatial working memory impairments compared to PD controls on DA (t = 2.13, df = 26, p = 0.04).ConclusionGreater impulsive choice, faster RT, faster decision conflict RT, and executive dysfunction may contribute to ICDs in PD.

Acute-alcohol effects on the Experiential Discounting Task (EDT) and a question-based measure of delay discounting.

Alcohol is widely believed to increase impulsive behavior. However, this has been difficult to demonstrate for impulsive choice using existing measures of delay discounting. We hypothesized a new real-time discounting task would be more sensitive to acute effects of alcohol. Measures included were a (a) question-based measure of delay discounting, the (b) Experiential Discounting Task (EDT), the (c) Balloon Analogue Risk Task (BART), the (d) Stop Task, and the (e) Go/No-Go Task. A three-session, double-blind, placebo-controlled, within-subjects design was used. Placebo, 0.4, or 0.8 g/kg alcohol doses were administered in a counterbalanced order over the three testing sessions. Twenty four (13 females) healthy social drinkers between the ages of 21 and 35 participated. Alcohol increased impulsive responding only on the EDT and the Stop Task. On the EDT, participants performed more impulsively after the 0.8 g/kg dose compared to placebo, whereas on the Stop Task, both the 0.4 and 0.8 g/kg doses increased impulsive responding. Alcohol had no significant effects on the other measures. The EDT was more sensitive to the acute effects of alcohol than previously used discounting tasks. Procedural differences between the EDT and question-based measures are discussed in the context of these divergent findings.

Individuals Family History Positive for Alcoholism Show Functional Magnetic Resonance Imaging Differences in Reward Sensitivity That Are Related to Impulsivity Factors

BACKGROUND Substance-abusing individuals tend to display abnormal reward processing and a vulnerability to being impulsive. Detoxified alcoholics show differences in regional brain activation during a monetary incentive delay task. However, there is limited information on whether this uncharacteristic behavior represents a biological predisposition toward alcohol abuse, a consequence of chronic alcohol use, or both. METHODS We investigated proposed neural correlates of substance disorder risk by examining reward system activity during a monetary incentive delay task with separate reward prospect, reward anticipation, and reward outcome phases in 30 individuals with and 19 without family histories of alcoholism. All subjects were healthy, lacked DSM-IV past or current alcohol or substance abuse histories, and were free of illegal substances as verified by a urine toxicology screening at the time of scanning. Additionally, we explored specific correlations between task-related nucleus accumbens (NAcc) activation and distinct factor analysis-derived domains of behavioral impulsivity. RESULTS During reward anticipation, functional magnetic resonance imaging data confirmed blunted NAcc activation in family history positive subjects. In addition, we found atypical activation in additional reward-associated brain regions during additional task phases. We further found a significant negative correlation between NAcc activation during reward anticipation and an impulsivity construct. CONCLUSIONS Overall, results demonstrate that sensitivity of the reward circuit, including NAcc, is functionally different in alcoholism family history positive individuals in multiple regards.

Laboratory and self-report assessments of impulsive behavior in adolescent daily smokers and nonsmokers

This research compared adolescent daily smokers (n=25) and nonsmokers (n=26) on different measures of impulsivity. Assessments included question-based measures of delay (DDQ) and probability (PDQ) discounting, a measure of behavioral disinhibition (go-stop task), and a self-report measure of impulsivity (Barratt Impulsiveness Scale-Adolescent). Adolescent smokers were more impulsive on the DDQ and Barratt Impulsiveness Scale--Adolescent but not on the PDQ or the go-stop task. However, there was a significant interaction between smoking status and gender on the go-stop task, with male smokers performing less impulsively on this measure than male nonsmokers--an effect not observed with the female adolescents. These findings indicate that adolescents who smoke cigarettes are more impulsive with respect to some, but not all, types of impulsivity than are adolescents who do not smoke.

Effects of methylphenidate on discounting of delayed rewards in attention deficit/hyperactivity disorder.

Impulsivity is a central component of attention deficit/hyperactivity disorder (ADHD). Delay discounting, or a preference for smaller, immediate rewards over larger, delayed rewards, is considered an important aspect of impulsivity, and delay-related impulsivity has been emphasized in etiological models of ADHD. In this study, we examined whether stimulant medication, an effective treatment for ADHD, reduced discounting of delayed experiential and hypothetical rewards among 49 children (ages 9-12 years) with ADHD. After a practice day, participants completed a 3-day double-blind placebo-controlled acute medication assessment. Active doses were long-acting methylphenidate (Concerta), with the nearest equivalents of 0.3 and 0.6 mg/kg TID immediate-release methylphenidate. On each testing day, participants completed experiential (real-world money in real time) and hypothetical discounting tasks. Relative to placebo, methylphenidate reduced discounting of delayed experiential rewards but not hypothetical rewards. Broadly consistent with etiological models that emphasize delay-related impulsivity among children with ADHD, these findings provide initial evidence that stimulant medication reduces delay discounting among those with the disorder. The results also draw attention to task parameters that may influence the sensitivity of various delay discounting measures to medication effects.

Do high rates of cigarette consumption increase delay discounting?: A cross-sectional comparison of adolescent smokers and young-adult smokers and nonsmokers

The present report attempts to help clarify the causal or consequent relation between frequently reported high rates of delay discounting (DD) associated with cigarette-smoking status in adults. Delay-discount functions of adolescent smokers and young-adult smokers and nonsmokers from two earlier studies [Reynolds, B., Karraker, K., Horn, K., Richards, J.B., 2003. Delay and probability discounting as related to different stages of adolescent smoking and non-smoking. Behav. Process. 64, 333-344; Reynolds, B., Richards, J.B., Horn, K., Karraker, K., 2004. Delay discounting and probability discounting as related to cigarette smoking status in adults. Behav. Process. 65, 35-42] were cross-sectionally compared. If a high rate of DD is a predisposing factor to future smoking status, adolescent and young-adult smokers were expected to have similar rates of DD, but both groups were expected to have higher rates of discounting than young-adult nonsmokers. Alternatively, if a high rate of cigarette consumption over an extended period is related to increases in DD, young-adult smokers were expected to discount more than adolescent smokers and young-adult nonsmokers. Results supported the hypothesis that a high rate of cigarette consumption is related to higher rates of DD, rather than the alternative hypothesis that smokers are predisposed with higher rates of DD. Also, after combining adolescent and young-adult smokers, self-reported number of cigarettes consumed per day was positively correlated with rate of DD; however, reported length of smoking history was not correlated with DD. Possible neurological mechanisms leading to increased discounting are discussed.

Role of Impulsivity in the Relationship Between Depression and Alcohol Problems Among Emerging Adult College Drinkers

Depression is common among college students and higher levels of depression are associated with greater alcohol-related problems. However, depression is frequently not found to be directly associated with more alcohol use. This study examined whether various aspects of impulsivity (negative urgency, lack of premeditation, lack of perseverance, sensation seeking, and delay discounting) and drinking to cope with negative affect help to account for the relationship between depression and alcohol problems among emerging adult college drinkers who reported at least a minimal level of depressive symptoms. In this cross-sectional study, 143 emerging adult (between 18 and 25 years old) female (69.9%, n = 100) and male (30.1%, n = 43) college drinkers with at least minimal depressive symptoms completed measures of depression, alcohol use and problems, drinking to cope, and impulsivity. A multiple mediation analysis revealed that only negative urgency and drinking to cope partially mediated the depression-alcohol problems relationship. Moderated mediation analyses revealed that impulsivity-related constructs did not significantly interact with drinking to cope to increase alcohol problems. It appears that alcohol use is particularly problematic for students with elevated depression, and this is partly attributable to depressions association with negative urgency, in addition to its association with drinking to cope. Our findings suggest that students who suffer from depression may engage in problematic drinking behavior in part because negative affect is detrimental to their short-term impulse control and decision making, independent of maladaptive attempts to regulate affect through drinking to cope.