Delay discounting and intelligence: A meta-analysis

Is it really self-control? Examining the predictive power of the delay of gratification task

This investigation tests whether the predictive power of the delay of gratification task (colloquially known as the "marshmallow test") derives from its assessment of self-control or of theoretically unrelated traits. Among 56 school-age children in Study 1, delay time was associated with concurrent teacher ratings of self-control and Big Five conscientiousness-but not with other personality traits, intelligence, or reward-related impulses. Likewise, among 966 preschool children in Study 2, delay time was consistently associated with concurrent parent and caregiver ratings of self-control but not with reward-related impulses. While delay time in Study 2 was also related to concurrently measured intelligence, predictive relations with academic, health, and social outcomes in adolescence were more consistently explained by ratings of effortful control. Collectively, these findings suggest that delay task performance may be influenced by extraneous traits, but its predictive power derives primarily from its assessment of self-control.

Temporal Discounting Is Associated with an Increased Risk of Mortality among Community-Based Older Persons without Dementia

Background

Temporal discounting is an important determinant of many health and financial outcomes, but we are not aware of studies that have examined the association of temporal discounting with mortality.

Methods

Participants were 406 older persons without dementia from the Rush Memory and Aging Project, a longitudinal cohort study of aging. Temporal discounting was measured using standard preference elicitation questions. Individual discount rates were estimated using a well-established hyperbolic function and used to predict the risk of mortality during up to 5 years of follow-up.

Results

The mean estimate of discounting was 0.45 (SD = 0.33, range: 0.08–0.90), with higher scores indicating a greater propensity to prefer smaller immediate rewards over larger but delayed ones. During up to 5 years of follow-up (mean = 3.6 years), 62 (15% of 406) persons died. In a proportional hazards model adjusted for age, sex, and education, temporal discounting was associated with an increased risk of mortality (HR = 1.103, 95% CI 1.024, 1.190, p = 0.010). Thus, a person with the highest discount rate (score = 0.90) was about twice more likely to die over the study period compared to a person with the lowest discount rate (score = 0.08). Further, the association of discounting with mortality persisted after adjustment for the level of global cognitive function, the burden of vascular risk factors and diseases, and an indicator of psychological well being (i.e., purpose in life).

Conclusion

Temporal discounting is associated with an increased risk of mortality in old age after accounting for global cognitive function and indicators of physical and mental health.

Domain-general and domain-specific aspects of temporal discounting in children with ADHD and autism spectrum disorders (ASD): a proof of concept study

It has been shown that delayed consumable rewards are discounted to a higher degree than money, which has been referred to as the "domain effect". Until now the effects of reward type on temporal discounting (TD) have mainly been studied in adults. Although there is evidence that children with attention-deficit/hyperactivity disorder (ADHD) tend to show steeper TD of money than typically developing peers or children with autism spectrum disorders (ASD), it remains untested whether the domain effect is also seen in children with ADHD and ASD. To explore this we compared TD of children (8-16 year) with ADHD, ASD and typically developing controls with five different reward types. Seventy-two participants with ADHD, 69 with ASD and 130 controls performed two hypothetical TD-tasks: a monetary TD-task and a TD-task with one of four alternative rewards (material rewards, rewarding activities, food, social rewards). TD was seen for all reward types, but the rate of discounting was steeper for food, praise and rewarding activities compared to money, and for food and praise compared to material rewards. For the ADHD and control groups, but not the ASD group, money and material rewards were equally highly discounted. High correlations between TD of money and of activities, food and material rewards were found. In conclusion, a domain effect was observed in typically developing children, as well as in children with ADHD or ASD, although the pattern was somewhat different for ASD children. Despite this domain effect, there is also evidence for a domain-general aspect in TD.

Effects of mindful eating training on delay and probability discounting for food and money in obese and healthy-weight individuals

Obese individuals tend to behave more impulsively than healthy weight individuals across a variety of measures, but it is unclear whether this pattern can be altered. The present study examined the effects of a mindful eating behavioral strategy on impulsive and risky choice patterns for hypothetical food and money. In Experiment 1, 304 participants completed computerized delay and probability discounting tasks for food-related and monetary outcomes. High percent body fat (PBF) predicted more impulsive choice for food, but not small-value money, replicating previous work. In Experiment 2, 102 randomly selected participants from Experiment 1 were assigned to participate in a 50-min workshop on mindful eating or to watch an educational video. They then completed the discounting tasks again. Participants who completed the mindful eating session showed more self-controlled and less risk-averse discounting patterns for food compared to baseline; those in the control condition discounted similarly to baseline rates. There were no changes in discounting for money for either group, suggesting stimulus specificity for food for the mindful eating condition.

Normative arguments from experts and peers reduce delay discounting

When making decisions that involve tradeoffs between the quality and timing of desirable outcomes, people consistently discount the value of future outcomes. A puzzling finding regarding such decisions is the extremely high rate at which people discount future monetary outcomes. Most economists would argue that decision-makers should turn down only rates of return that are lower than those available to them elsewhere. Yet the vast majority of studies find discount rates that are significantly higher than market interest rates (Frederick et al., 2002). Here we ask whether a lack of knowledge about the normative strategy can explain high discount rates. In an initial experiment, nearly half of subjects did not spontaneously cite elements of the normative strategy when asked how people should make intertemporal monetary decisions. In two follow-up experiments, after subjects read a “financial guide” detailing the normative strategy, discount rates declined by up to 85%, but were still higher than market interest rates. This decline persisted, though attenuated, for at least one month. In a final experiment, peer-generated advice influenced discount rates in a similar manner to “expert” advice, and arguments focusing on normative considerations were at least as effective as others. These studies show that part of the explanation for high discount rates is a lack of knowledge regarding the normative strategy, and they quantify how much discount rates are reduced in response to normative arguments. Given the high level of discounting that remains, however, there are other contributing factors to high discount rates that remain to be quantified.

Association of cognition with temporal discounting in community based older persons

BACKGROUND

The objective of this study was to test the hypothesis that cognitive function is negatively associated with temporal discounting in old age.

METHODS

Participants were 388 community-dwelling older persons without dementia from the Rush Memory and Aging Project, an ongoing longitudinal epidemiologic study of aging in the Chicago metropolitan area. Temporal discounting was measured using standard questions in which participants were asked to choose between an immediate, smaller payment and a delayed, larger one. Cognition was measured using a detailed battery including 19 tests. The association between cognition and temporal discounting was examined via mixed models adjusted for age, sex, education, income, and the number of chronic medical conditions.

RESULTS

Descriptive data revealed a consistent pattern whereby older persons with lower cognitive function were more likely to discount greater but delayed rewards compared to those with higher cognitive function. Further, in a mixed effect model adjusted for age, sex, education, income, and chronic medical conditions, global cognitive function was negatively associated with temporal discounting (estimate = -0.45, SE = 0.18, p = 0.015), such that a person with lower cognition exhibited greater discounting. Finally, in subsequent models examining domain specific associations, perceptual speed and visuospatial abilities were associated with temporal discounting, but episodic memory, semantic memory and working memory were not.

CONCLUSION

Among older persons without dementia, a lower level of cognitive function is associated with greater temporal discounting. These findings have implications regarding the ability of older persons to make decisions that involve delayed rewards but maximize well-being.

Age modulates the effect of COMT genotype on delay discounting behavior

RATIONALE AND OBJECTIVE

A form of impulsivity, the tendency to choose immediate over delayed rewards (delay-discounting) has been associated with a single nucleotide polymorphism (SNP) in the catechol-O-methyltransferase (COMT) gene (COMTval¹⁵⁸met; rs4680). However, the existing data regarding the nature of this association are in conflict. We have previously reported that adults homozygous for valine (val) at the COMTval¹⁵⁸met SNP demonstrate greater delay-discounting than do methionine (met) allele carriers (Boettiger et al., J Neurosci 27:14383-14391, 2007). In contrast, a recent study of adolescent males found that those with the met/met genotype demonstrate greater delay-discounting than do val-allele carriers (Paloyelis et al., Neuropsychopharmacology 35:2414-2426, 2010). Based on reported age-related changes in frontal dopamine function and COMT expression, we hypothesized that the association of COMT genotype with delay-discounting behavior is modulated by age from late adolescence to young adulthood.

METHODS

To test this hypothesis, we genotyped late adolescents (18-21 years; n = 72) and adults (22-40 years; n = 70) for the COMTval¹⁵⁸met polymorphism, measured their delay-discounting behavior, and tested for an interaction between age group and COMT genotype.

RESULTS

This cross-sectional study found that age modulates COMTval¹⁵⁸met genotype effects on delay-discounting behavior. Among met-carriers, delay-discounting was negatively correlated with age from late adolescence to adulthood, while among val/val individuals delay-discounting was positively correlated with age across this range.

CONCLUSIONS

These results confirm our previous finding of enhanced delay-discounting among val/val adults relative to met-allele carriers, and help reconcile existing literature. We propose a single U-shaped model of the relationship between frontal DA levels and impulsive choice that accounts for both adolescent and adult data.

Cognitive ability, neighborhood deprivation, and young children's emotional and behavioral problems

PURPOSE

To examine if cognitive ability moderates the effect of area (neighborhood) deprivation on young children's problem behavior.

METHODS

Data from the first two sweeps of the Millennium Cohort Study (MCS) in the UK were used. Children were clustered in small areas in nine strata in the UK and were aged 9 months at Sweep 1 and 3 years at Sweep 2. Neighborhood deprivation was measured with the Index of Multiple Deprivation at Sweep 1. Overall and specific problem behavior was measured with the Strengths and Difficulties Questionnaire at Sweep 2. To explore moderator specificity we used three indices of ability (verbal cognitive ability, non-verbal cognitive ability, and attainment of developmental milestones). Adjustment was made for child's age and sex, and for Sweep 1 family adversity (number of adverse life events), family structure, mother's social class and psychological distress, and family socio-economic disadvantage.

RESULTS

We found both support for our main hypothesis, and evidence for specificity. Neighborhood deprivation was, even after adjustment for covariates, significantly associated with children's peer problems. However, verbal and non-verbal cognitive ability moderated this association.

CONCLUSIONS

Neighborhood deprivation was related to peer problems even at preschool age. Although the effect of neighborhood deprivation on externalizing problems was mediated by family poverty and parental socio-economic position and although its effect on internalizing problems was mediated by parental mental health, its effect on difficulties with peers was independent of both parental and child characteristics. Cognitive ability moderated the effect of neighborhood deprivation on preschoolers' peer relationships difficulties.

Cognitive control links alcohol use, trait disinhibition, and reduced cognitive capacity: Evidence for medial prefrontal cortex dysregulation during reward-seeking behavior

BACKGROUND

Guided by the prediction of response-outcome theory of cognitive control (Alexander and Brown, 2010a), the present study examined reward-seeking medial prefrontal cortex (mPFC) activity as a common neuro-functional marker of excessive alcohol consumption, trait disinhibition, and reduced cognitive capacity; all of which have shown consistent patterns of covariation in previous psychometric research (e.g., Bogg and Finn, 2010).

METHODS

A sample of 18-23-year-old university students with a heterogeneous prevalence of alcohol dependence was assessed with functional magnetic resonance imaging (fMRI) while completing a version of the Balloon Analogue Risk Task (Lejuez et al., 2002). A follow-back typical weekly alcohol consumption interview, self-report measures of trait disinhibition and IQ, and a complex span working memory task also were administered.

RESULTS

Correlational region-of-interest analyses showed greater typical weekly alcohol consumption, greater trait disinhibition, and lower IQ were associated with greater reductions in mPFC activity during reward-seeking behaviors (successive inflation choices). The results also showed greater typical weekly alcohol consumption, greater trait disinhibition, and lower IQ were associated with greater increases in mPFC activity during reward-seeking outcomes (successive successful inflation outcomes). No significant relations with the measure of working memory were found.

CONCLUSIONS

The findings suggest mPFC activity during risk/reward appraisal and performance monitoring is a common neuro-functional feature of co-varying expressions of excessive alcohol consumption, trait disinhibition, and lower IQ.

Polymorphic variation in the dopamine D4 receptor predicts delay discounting as a function of childhood socioeconomic status: evidence for differential susceptibility

Inconsistent or null findings among studies associating behaviors on the externalizing spectrum--addictions, impulsivity, risk-taking, novelty-seeking traits--with presence of the 7-repeat allele of a common length polymorphism in the gene encoding the dopamine D4 receptor (DRD4) may stem from individuals' variable exposures to prominent environmental moderators (gene × environment interaction). Here, we report that relative preference for immediate, smaller rewards over larger rewards delayed in time (delay discounting), a behavioral endophenotype of impulsive decision-making, varied by interaction of DRD4 genotype with childhood socioeconomic status (SES) among 546 mid-life community volunteers. Independent of age, sex, adulthood SES and IQ, participants who were both raised in families of distinctly low SES (low parental education and occupational grade) and carried the DRD4 7-repeat allele discounted future rewards more steeply than like-reared counterparts of alternate DRD4 genotype. In the absence of childhood socioeconomic disadvantage, however, participants carrying the 7-repeat allele discounted future rewards less steeply. This bidirectional association of DRD4 genotype with temporal discounting, conditioned by participants' early life circumstances, accords with a recently proposed developmental model of gene × environment interaction ('differential susceptibility') that posits genetically modulated sensitivity to both adverse and salubrious environmental influences.

Now for Me, Later for Us? Effects of Group Context on Temporal Discounting

Delayed rewards are less valuable than immediate rewards. This well-established finding has focused almost entirely on individual outcomes. However, are delayed rewards similarly discounted if they are shared by a group? The current article reports on three experiments exploring the effect of group context on delay discounting. Results indicate that discount rates of individual and group rewards were highly correlated, but that respondents were more willing to wait (decreased discounting) for shared outcomes than for individual outcomes. An explanatory model is proposed suggesting that decreased discount rates in group contexts may be due to the way the effects of both delay and social discounting are combined. That is, in a group context, a person values both a future reward (discounted by delay) and a present reward to another person (discounted by the social distance between them). The results are explained by a combined discount function containing a delay factor and a factor representing the social distance between the decision maker and group members. Practical implications of the fact that shared consequences can increase individual self-control are also discussed.

Delay discounting, impulsiveness, and addiction severity in opioid-dependent patients

Individuals who abuse drugs show higher delay discounting (DD) rate and impulsiveness scores compared with controls; however, it is unclear if DD rate covaries with severity of the addiction or if an individual's discounting rate can be changed by effective substance abuse treatment. This study compared methadone maintenance treatment (MMT) patients (n = 30) who had not used illegal drugs for 2 years with drug-using MMT patients (n = 30) and controls (n = 25) in terms of addiction severity, DD rate, and impulsiveness. Methadone patients abstinent from illegal drugs scored significantly lower on a number of addiction severity measures than the drug-using methadone patients. In addition, both groups of MMT patients showed significantly higher rates of DD and impulsiveness than the control group; however, no differences in DD rate or impulsiveness were found between the groups of patients. Results suggest that DD rate and impulsiveness may not covary with indicators of addiction severity in MMT patients.

Consequences of age-related cognitive declines

Adult age differences in a variety of cognitive abilities are well documented, and many of those abilities have been found to be related to success in the workplace and in everyday life. However, increased age is seldom associated with lower levels of real-world functioning, and the reasons for this lab-life discrepancy are not well understood. This article briefly reviews research concerned with relations of age to cognition, relations of cognition to successful functioning outside the laboratory, and relations of age to measures of work performance and achievement. The final section discusses several possible explanations for why there are often little or no consequences of age-related cognitive declines in everyday functioning.

Genetic origins of the association between verbal ability and alcohol dependence symptoms in young adulthood

BACKGROUND

Cognitive deficits in alcohol dependence (AD) have been observed, poorer verbal ability being among the most consistent findings. Genetic factors influence both cognitive ability and AD, but whether these influences overlap is not known.

METHOD

A subset of 602 monozygotic (MZ) and dizygotic (DZ) twins from FinnTwin16, a population-based study of Finnish twins, was used to study the associations of verbal ability with DSM-III-R diagnosis and symptoms of AD, the maximum number of drinks consumed in a 24-h period, and the Rutgers Alcohol Problem Index (RAPI) scores. These twins, most of them selected for within-pair discordance or concordance for their RAPI scores at age 18.5 years, were studied with neuropsychological tests and interviewed with the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) in young adulthood (mean age 26.2 years, range 23-30 years).

RESULTS

All alcohol problem measures were associated with lower scores on the Vocabulary subtest of the Wechsler Adult Intelligence Scale - Revised (WAIS-R), a measure of verbal ability. In bivariate genetic models, Vocabulary and the alcohol problem measures had moderate heritabilities (0.54-0.72), and their covariation could be explained by correlated genetic influences (genetic correlations -0.20 to -0.31).

CONCLUSIONS

Poorer verbal ability and AD have partly overlapping biological etiology. The genetic and environmental influences on the development of cognitive abilities, alcohol problems and risk factors for AD should be studied further with prospective longitudinal designs.

Delay discounting of reward in ADHD: application in young children

BACKGROUND

A key underlying process that may contribute to attention-deficit/hyperactivity disorder (ADHD) involves alterations in reward evaluation, including assessing the relative value of immediate over delayed rewards. This study examines whether children with ADHD discount the value of delayed rewards to a greater degree than typically developing children using a delay discounting task.

METHODS

Children aged 7-9 years diagnosed with ADHD and controls completed a task in which they chose between a hypothetical $10 available after a delay (7, 30, 90 and 180 days) versus various amounts available immediately.

RESULTS

ADHD participants discounted more steeply than controls. However, this effect did not survive covarying of IQ.

CONCLUSIONS

ADHD is associated with a steeper delay gradient when contemplating hypothetical later rewards, but not independently of IQ. The interplay of cognitive processing and IQ with reward evaluation in ADHD requires further exploration.

Self-controlled children stay leaner in the transition to adolescence

In a prospective longitudinal study, we examined whether the personality trait of self-control protects against weight gain during the transition from childhood to adolescence. We obtained multi-method, multi-source measures of self-control from a socioeconomically and ethnically diverse sample of 105 fifth-grade students. Height and weight were recorded by the school nurse and used to calculate age- and gender-specific standardized body mass index (BMI) z-scores. Self-controlled fifth graders had lower BMI z-scores in eighth grade compared to their more impulsive peers, and this relationship remained significant when controlling for potential confounds, including gender, age, socioeconomic status, ethnicity, IQ, and happiness. Moreover, when controlling for the same covariates, self-control measured in fifth grade predicted decreases in BMI z-scores from fifth to eighth grade. These results suggest that more self-controlled children are protected from weight gain in the transition to adolescence.

Performance in temporal discounting tasks by people with intellectual disabilities reveals difficulties in decision-making and impulse control

The subjective value of rewards declines as a function of the delay to receive them (temporal discounting). Three temporal discounting tasks that assessed preferences between small amounts of money (10 pence) over short delays (60 s), moderate amounts of money (10 pound) over moderate delays (2 weeks), and large amounts of money (1000 pound) over long delays (12 months) were presented to people with intellectual disabilities (Full-Scale IQ < 70) and to a comparison group (ns = 20 for each group). Measures of IQ, financial knowledge, memory, and executive functioning were also obtained. Only a third of the service users were able to perform the temporal discounting tasks consistently, and they tended to respond impulsively. The proportion of participants responding consistently increased following training. Both the initial performance and the effect of training were related to executive functioning but not IQ.

Neuroeconomics: what have we found, and what should we search for

Neuroeconomics is an interdisciplinary field, crossing boundaries between Economics, Psychology, and Neuroscience. Its original program was to provide a test for a large number of competitive theories of decision making. It has in part realized this program, and we review the main findings here. But its results are also posing the need for a new theoretical unifying framework. We outline a possible line of future research.

Individual differences in delay discounting: relation to intelligence, working memory, and anterior prefrontal cortex

Lower delay discounting (better self-control) is linked to higher intelligence, but the basis of this relation is uncertain. To investigate the potential role of working memory (WM) processes, we assessed delay discounting, intelligence (g), WM (span tasks, 3-back task), and WM-related neural activity (using functional magnetic resonance imaging) in 103 healthy adults. Delay discounting was negatively correlated with g and WM. WM explained no variance in delay discounting beyond that explained by g, which suggests that processes through which WM relates to delay discounting are shared by g. WM-related neural activity in left anterior prefrontal cortex (Brodmann's area 10) covaried with g, r= .26, and delay discounting, r=-.40, and partially mediated the relation between g and delay discounting. Overall, the results suggest that delay discounting is associated with intelligence in part because of processes instantiated in anterior prefrontal cortex, a region known to support the integration of diverse information.

Individual laboratory-measured discount rates predict field behavior

We estimate discount rates of 555 subjects using a laboratory task and find that these individual discount rates predict inter-individual variation in field behaviors (e.g., exercise, BMI, smoking). The correlation between the discount rate and each field behavior is small: none exceeds 0.28 and many are near 0. However, the discount rate has at least as much predictive power as any variable in our dataset (e.g., sex, age, education). The correlation between the discount rate and field behavior rises when field behaviors are aggregated: these correlations range from 0.09-0.38. We present a model that explains why specific intertemporal choice behaviors are only weakly correlated with discount rates, even though discount rates robustly predict aggregates of intertemporal decisions.