Regular ArticleModeling Myopic Decisions: Evidence for Hyperbolic Delay-Discounting within Subjects and Amounts
Abstract
Hyperbolic and exponential discounting functions were compared as models of subjects′ present valuations of delayed rewards. Previous comparisons have been limited by relying on the assumption that discounting rate is independent of reward size; we avoided this limitation by making all comparisons within reward sizes. In Experiment 1, using real rewards in a simulated auction, and in Experiment 2, using hypothetical rewards, we offered subjects five monetary rewards at six delays each and asked them to indicate the smallest amount that they would accept immediately in exchange for those rewards. Both discounting functions were then fit to the six reported amounts for each reward using nonlinear regressions. In both experiments, although both functions fit the data very well, the hyperbolic function fit better for all of the delayed rewards. Furthermore, the hyperbolic function better described the data for 20 of 21 and 14 of 18 subjects in Experiments 1 and 2, respectively.
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Decision conflicts may arise when the costs and benefits of choices are evaluated as a function of outcomes predicted along a temporal dimension. Electrophysiology studies suggest that during performance monitoring a typical oscillatory activity in the theta rhythm, named midfrontal theta, may index conflict processing and resolution. In the present within-subject, sham controlled, cross-over preregistered study, we delivered online midfrontal transcranial Alternating Current Stimulation (tACS) to modulate electrocortical activity during intertemporal decisions. Participants were invited to select choice preference between economic offers at three different intermixed levels of conflict (i.e., low, medium, high) while receiving either theta -, gamma-, or sham tACS in separate blocks and sessions. At the end of each stimulation block, a Letter-Flanker task was also administered to measure behavioural aftereffects. We hypothesized that theta-tACS would have acted on the performance monitoring system inducing behavioural changes (i.e., faster decisions and more impulsive choices) in high conflicting trials, rather than gamma- and sham-tACS. Results very partially confirmed our predictions. Unexpectedly, both theta- and gamma-driven neuromodulation speeded-up decisions compared to sham. However, exploratory analyses revealed that such an effect was stronger in the high-conflict decisions during theta-tACS. These findings were independent from the influence of the sensations induced by the electrical stimulation. Moreover, further analyses highlighted a significant association during theta-tACS between the selection of immediate offers in high-conflict trials and attentional impulsiveness, suggesting that individual factors may account for the tACS effects during intertemporal decisions. Finally, we did not capture long-lasting behavioural changes following tACS in the Flanker task. Our findings may inform scholars to improve experimental designs and boost the knowledge toward a more effective application of tACS.
Evidence accumulation is not essential for generating intertemporal preference: A comparison of dynamic cognitive models of matching tasks
2023, Cognitive PsychologyIntertemporal preference has been investigated mainly with a choice paradigm. However, a matching paradigm might be more informative for a proper inference about intertemporal preference and a deep understanding of the underlying cognitive mechanisms. This research involved two empirical studies using the matching paradigm and compared various corresponding dynamic models. These models were developed under either the framework of decision field theory, an exemplar theory assuming evidence accumulation, or a non-evidence-accumulation framework built upon the well-established notions of random utility and discrimination threshold (i.e., the RUDT framework). Most of these models were alternative-based whereas the others were attribute-based ones. Participants in Study 1 were required to fill in the amount of an immediate stimulus to make it as attractive as a delayed stimulus, whereas those in Study 2 needed to accomplish a more general matching task in which either the payoff amount or delay length of one stimulus was missing. Consistent behavioral regularities regarding both matching values and response times were revealed in these studies. The results of model comparison favored in general the RUDT framework as well as an attribute-based perspective on intertemporal preference. In addition, the predicted matching values and response times of the best RUDT model were also highly correlated with the observed data and replicated most observed behavioral regularities. Together, this research and previous modeling work on intertemporal choice suggest that evidence accumulation is not essential for generating intertemporal preference. Future research should examine the validity of the new framework in other preferential decisions for a more stringent test of the framework.
Diagnostic group differences and exploratory sex differences in intrinsic connectivity during fMRI Stroop in individuals with and without cocaine use disorder
2023, Drug and Alcohol DependenceSex-/gender-related differences in cognitive control and how they relate to addictions may inform novel treatment options. Cognitive control, including Stroop performance, has been linked to addictions and treatment outcomes. The extent to which women and men with cocaine use disorder (CUD) show brain and behavioral differences relating to Stroop performance has not been previously studied. We examined sex-related differences in Stroop-related brain connectivity in female and male CUD and healthy-comparison (HC) subjects.
40 individuals with CUD (20 female) and 40 HC (20 female) subjects matched on age, race, and ethnicity completed an fMRI Stroop task. Intrinsic connectivity distribution (ICD) and mean-adjusted ICD analyses were conducted to identify differences related to sex and diagnostic group. Stroop task performance was also considered.
Behavioral results confirmed a Stroop effect. A main effect of diagnostic group indicated that the CUD versus HC group showed lower connectivity in the prefrontal cortex, frontal gyrus, cingulate gyrus, precuneus, cerebellum, and somatosensory, visual, and auditory areas. An exploratory main effect of sex suggested that males may show relatively lower connectivity than females in the cerebellum and brainstem, although connectivity was largely similar across sexes.
Intrinsic connectivity during cognitive control varied by diagnostic group and possibly by sex. The findings suggest that interventions targeting cognitive control in CUD should consider sex.
Delay discounting in Parkinson's disease: A systematic review and meta-analysis
2023, Behavioural Brain ResearchDelay discounting refers to the depreciation of the value of a reward as a function of the time it takes to obtain it. Growing evidence shows altered delay discounting in several pathological conditions, including neurological disorders. Here, we conducted a systematic review and meta-analysis of the published literature on delay discounting (DD) in Parkinson’s Disease (PD). We found steeper DD in patients with PD, compared to healthy controls, both in “on” and “off” dopaminergic medication. These results confirm altered DD in PD and suggest an independent influence of the dopaminergic medication and the clinical condition itself on it. Also the effect of impulse control disorder and of pharmacological treatments are analysed.
Can hypothetical measures of time preference predict actual and incentivised behaviour? Evidence from Senegal.
2022, World DevelopmentTime preferences are an important determinant of decision-making and are widely measured through hypothetical survey questions. However, the extent to which they offer a good representation of time discounting remains largely unexplored. This paper estimates time preference parameters using a commonly-applied hypothetical elicitation method. We explore whether our estimated parameters correlate with actual and incentivized behaviours related to time preferences. First, we consider the correlation between our hypothetical measures and the result of an incentivised experiment using the unique reference numbers of banknotes as a means of determining an individual’s willingness to save money. Individuals are given a banknote and informed that if they chose to retain this specific note for a randomly assigned period of time (2, 7 or 14 days) they will receive a second banknote, in effect doubling their initial endowment. Second, we consider the correlation between hypothetical measures and an individual’s observable saving behaviour, including ownership of a savings account and participation in a Rotating Credit and Savings Association (ROSCA). Overall, our results show that hypothetically-derived time preference parameters are not significantly correlated with our measures of actual or incentivized behaviour. We explore the extent to which our results are due to limited power and find that a version of our results comparable to the relevant literature can detect effect sizes in line with similar studies. Furthermore, we recognise that our incentivized experiment will be a noisy reflection of time discounting and subject to confounding factors, such as the inherent fungibility of money. We provide ancillary evidence suggesting that our main results remain robust to these considerations and others.
The role of social value orientation on delay discounting in a group context
2022, Personality and Individual DifferencesTwo studies examined the role of social value orientation (SVO) on group-context delay discounting (GDD). SVO classifications were determined from responses on the Decomposed Prisoner's Dilemma game. GDD was assessed with a version of the Monetary Choice Questionnaire, where participants indicated preference between immediate and delayed hypothetical monetary rewards for themselves and an “Other.” Study 1 compared GDD among the three SVO classifications. Results found that Competitors had the highest rate of GDD with no difference between Prosocials and Individualists (ηp2 = 0.0488). Given unbalanced distribution of SVO classifications, Study 2 incorporated valence (e.g., like versus dislike) as a factor for the “Other” in the SVO and GDD tasks. Having a “disliked Other” in the SVO task resulted in a more equal distribution across SVO classifications, and comparison of GDD between these groups replicated the finding from Study 1 that Competitors exhibited higher GDD compared to Prosocials (ηp2 = 0.0193). Overall, these findings suggest that SVO is an important individual-level factor that moderates the impact of group context on delay discounting.