Validation of a novel effort-discounting assessment and evaluation of the effort-delay confound on effort discounting.

A vast literature highlights the prevalence of impulsive decision making in maladaptive outcomes. Most research has focused on one form-delay discounting. Less research has focused on effort discounting, possibly because of a lack of a standardized task for assessment. In published effort-discounting tasks, effort is conceptualized in many ways, making it difficult to compare findings across studies. Additionally, most effort-discounting tasks do not control for the time inherent in completing the effortful task, which makes it difficult to disentangle effort discounting from delay discounting. The current study evaluated the validity of a novel hypothetical effort-discounting task. The novel task was used to evaluate the influence of the effort-delay confound on rates of effort discounting in humans. Participants were randomly assigned to complete a confounded or a controlled version of the novel effort-discounting task. The effort-discounting data were well described by hyperbolic and exponential functions. When effort and delay were confounded, effort-discounting rates were significantly higher than when effort alone influenced discounting. The results suggest that data that are produced by effort-discounting tasks that do not control the effort-delay confound should be interpreted cautiously because they are also influenced by delay discounting. Task limitations and future directions are discussed.

The impact of subclinical psychotic symptoms on delay and effort discounting: Insights from behavioral, computational, and electrophysiological methods.

BACKGROUND: The ability to value rewards is crucial for adaptive behavior and is influenced by the time and effort required to obtain them. Impairments in these computations have been observed in patients with schizophrenia and may be present in individuals with subclinical psychotic symptoms (PS). METHODS: In this study, we employed delay and effort-discounting tasks with food rewards in thirty-nine participants divided into high and low levels of PS. We investigated the underlying mechanisms of effort-discounting through computational modelling of dopamine prefrontal and subcortical circuits and the electrophysiological biomarker of both delay and effort-discounting alterations through resting-state frontal alpha asymmetry (FAA). RESULTS: Results revealed greater delay discounting in the High PS group compared to the Low PS group but no differences in the effort discounting task. However, in this task, the same levels of estimated dopamine release were associated with a lower willingness to exert effort for high-calorie food rewards in High PS participants compared to Low PS participants. Although there were no significant differences in FAA between the High PS and Low PS groups, FAA was significantly associated with the severity of participants' negative symptoms. CONCLUSIONS: Our study suggests that the dysfunction in temporal and effort cost computations, seen in patients with schizophrenia, may be present in individuals with subclinical PS. These findings provide valuable insight into the early vulnerability markers (behavioral, computational, and electrophysiological) for psychosis, which may aid in the development of preventive interventions. These findings are preliminary and warrant further investigation.

Social Effort Discounting Reveals Domain-General and Social-Specific Motivation Components.

BACKGROUND: Social motivation is crucial for healthy interpersonal connections and is impaired in a subset of the general population and across many psychiatric disorders. However, compared with nonsocial (e.g., monetary) motivation, social motivation has been understudied in quantitative behavioral work, especially regarding willingness to exert social effort. We developed a novel social effort discounting task, paired with a monetary task to examine motivational specificity. We expected that social task performance would relate to general motivation and also show selective relationships with self-reported avoidance tendencies and with sociality. METHODS: An analyzed sample of 397 participants performed the social and nonsocial effort discounting task online, along with self-report measures of various aspects of motivation and psychiatric symptomatology. RESULTS: Social and nonsocial task motivation correlated strongly (ρ = 0.71, p < .001). Both social and nonsocial task motivation related similarly to self-reported general motivation (social, ß = 0.16; nonsocial, ß = 0.13) and to self-reported approach motivation (social, ß = 0.14; nonsocial, ß = 0.11), with this common effect captured by a significant main effect across social and nonsocial conditions. Significant condition interaction effects supported a selective relationship of social task motivation with self-reported sociality and also with avoidance motivation. CONCLUSIONS: Our novel social effort discounting task revealed both domain-general and social-specific components of motivation. In combination with other measures, this approach can facilitate further investigation of common and dissociable neurobehavioral mechanisms to better characterize normative and pathological variation and develop personalized interventions targeting specific contributors to social impairment.

Does effort increase or decrease reward valuation? Considerations from cognitive dissonance theory.

The present research tested the effect of manipulated perceived control (over obtaining the outcomes) and effort on reward valuation using the event-related potential known as the Reward Positivity (RewP). This test was conducted in an attempt to integrate two research literatures with opposite findings: Effort justification occurs when high effort leads to high reward valuation, whereas effort discounting occurs when high effort leads to low reward valuation. Based on an examination of past methods used in these literatures, we predicted that perceived control and effort would interactively influence RewP. Consistent with the effort justification literature (cognitive dissonance theory), when individuals have high perceived control, high effort should lead to more reward valuation than low effort should. Consistent with the effort discounting literature, when individuals have low perceived control, low effort should lead to more reward valuation than high effort should. Results supported these interactive and integrative predictions.

Effort and effort discounting as predictors of seeking psychotherapy among individuals with depression.

OBJECTIVES: Many individuals who experience depression do not seek psychotherapy, and past research has had limited success in predicting help-seeking in this population. Accounting for behavioral characteristics of depression that affect help-seeking decisions, such as effort discounting (devaluation of rewards as a function of effort), may address this gap. METHODS: Individuals with moderate-severe depression symptoms who were not in psychotherapy (N = 253) reported their depression symptom severity and the amount of effort they anticipated seeking psychotherapy would require; they also completed a behavioral measure of effort discounting. At a 3-month follow-up, they reported whether they initiated psychotherapy during the follow-up period. RESULTS: Depression symptom severity was associated with perceptions that seeking psychotherapy would be more effortful. In turn, perceptions that seeking psychotherapy would be more effortful prospectively predicted a lower likelihood of initiating psychotherapy. Effort discounting was unrelated to psychotherapy use. CONCLUSIONS: These results suggest that differences in the anticipated effort required to seek psychotherapy can increase depressed individuals' risk of going untreated. Future research may test whether reducing the effort of seeking psychotherapy increases psychotherapy use among those with depression. For instance, streamlining insurance enrollment procedures, implementing patient decision aids, or offering telehealth treatment options may be beneficial.

Toward a Unifying Account of Dopamine's Role in Cost-Benefit Decision Making.

Dopamine is thought to play a crucial role in cost-benefit decision making, but so far there is no consensus on the precise role of dopamine in decision making. Here, we review the literature on dopaminergic manipulations of cost-benefit decision making in humans and evaluate how well different theoretical accounts explain the existing body of evidence. Reduced D2 stimulation tends to increase the willingness to bear delay and risk costs (i.e., wait for later rewards, take riskier options), while increased D1 and D2 receptor stimulation increases willingness to bear effort costs. We argue that the empirical findings can best be explained by combining the strengths of two theoretical accounts: in cost-benefit decision making, dopamine may play a dual role both in promoting the pursuit of psychologically close options (e.g., sooner and safer rewards) and in computing which costs are acceptable for a reward at stake. Moreover, we identify several limiting factors in the study designs of previous investigations that prevented a fuller understanding of dopamine's role in value-based choice. Together, the proposed theoretical framework and the methodological suggestions for future studies may bring us closer to a unifying account of dopamine in healthy and impaired cost-benefit decision making.

Moderate Stability among Delay, Probability, and Effort Discounting in Humans.

The stability of delay discounting across time has been well-established. However, limited research has examined the stability of probability discounting, and no studies of the stability of effort discounting are available. The present study assessed the steady-state characteristics of delay, probability, and effort discounting tasks across time with hypothetical rewards in humans, as well as whether response characteristics suggested a common discounting equation. Participants completed delay, probability, and effort discounting tasks on three occasions. We found moderate relative stability of delay and probability tasks, and similar evidence for absolute stability across time for all tasks. The interclass correlations coefficient showed some correspondence across time points and tasks, and higher levels of between subject variability, especially for the effort discounting task, suggesting trait level variables has a stronger influence on performance than state level variables. Performance on the delay and probability tasks were moderately correlated and similar mathematical functions fit choice patterns on both tasks (hyperbolic), suggesting that delay and probability discounting processes shared some common elements. Lower correlations and different function fits suggested that effort discounting involves more unique features.

Taking the path of least resistance now, but not later: Pushing cognitive effort into the future reduces effort discounting.

Effort discounting describes the devaluation of rewards that require effort to obtain. The present study investigated whether discounting of cognitive effort depends on how near the effort is in time. The present study also investigated whether effort discounting, and its modulation by temporal distance to the effort, might depend on need for cognition, a personality trait that describes how much one enjoys cognitively demanding tasks. Participants performed a validated effort discounting task that measured the extent to which they subjectively devalued a $20 reward when effort was required to receive it. Immediacy of the effort was manipulated by having participants imagine exerting varying levels of effort either immediately, in a day, or in a month. Results revealed linear increases in discounting of rewards as a function of both how much effort was involved and how imminent the effort was. The extent to which both these variables influenced discounting correlated with need for cognition. Individuals low in need for cognition exhibited more effort discounting overall and a linear increase in effort discounting as the effort grew imminent. Individuals high in need for cognition engaged in less effort discounting, which was not modulated by how imminent the effort was. These results indicate that people exhibit dynamic inconsistency in effort-related decisions, such that the degree to which they discount effort depends on how soon the effort is. Additionally, this tendency is linked with systematic individual differences in need for cognition. Lastly, this study demonstrates that these tendencies can be quantitatively operationalized.

Economic Choice and Heart Rate Fractal Scaling Indicate That Cognitive Effort Is Reduced by Depression and Boosted by Sad Mood.

BACKGROUND: People with depression typically exhibit diminished cognitive control. Control is subjectively costly, prompting speculation that control deficits reflect reduced cognitive effort. Evidence that people with depression exert less cognitive effort is mixed, however, and motivation may depend on state affect. METHODS: We used a cognitive effort discounting task to measure propensity to expend cognitive effort and fractal structure in the temporal dynamics of interbeat intervals to assess on-task effort exertion for 49 healthy control subjects, 36 people with current depression, and 67 people with remitted depression. RESULTS: People with depression discounted more steeply, indicating that they were less willing to exert cognitive effort than people with remitted depression and never-depressed control subjects. Also, steeper discounting predicted worse functioning in daily life. Surprisingly, a sad mood induction selectively boosted motivation among participants with depression, erasing differences between them and control subjects. During task performance, depressed participants with the lowest cognitive motivation showed blunted autonomic reactivity as a function of load. CONCLUSIONS: Discounting patterns supported the hypothesis that people with current depression would be less willing to exert cognitive effort, and steeper discounting predicted lower global functioning in daily life. Heart rate fractal scaling proved to be a highly sensitive index of cognitive load, and data implied that people with lower motivation for cognitive effort had a diminished physiological capacity to respond to rising cognitive demands. State affect appeared to influence motivation among people with current depression given that they were more willing to exert cognitive effort following a sad mood induction.

Everything comes at a price: Considerations in modeling effort-based choice.

When observing human behavior, one of the key factors determining choice is effort. It is often assumed that people prefer an easier course of action when the alternative yields the same benefits. However, recent research demonstrates that this is not always the case: effort is not always costly and can also add value. A promising avenue to study effort-based choice is to utilize formal decision models that enable quantitative modeling. In this paper, we aim to present an overview of the current approaches to modeling effort-based choice and discuss some considerations that stem from theoretical and practical issues (present and previous) in studies on the role of effort, focusing on the connections and discrepancies between formal models and the findings from the body of empirical research. Considering that effort can, in some circumstances, act as a cost and as a benefit, reconciling these discrepancies is a practical and theoretical challenge that can ultimately lead to better predictions and increased model validity. Our review identifies and discusses these discrepancies providing direction for future empirical research.

The Cost of Imagined Actions in a Reward-Valuation Task.

Growing evidence suggests that humans and other animals assign value to a stimulus based not only on its inherent rewarding properties, but also on the costs of the action required to obtain it, such as the cost of time. Here, we examined whether such cost also occurs for mentally simulated actions. Healthy volunteers indicated their subjective value for snack foods while the time to imagine performing the action to obtain the different stimuli was manipulated. In each trial, the picture of one food item and a home position connected through a path were displayed on a computer screen. The path could be either large or thin. Participants first rated the stimulus, and then imagined moving the mouse cursor along the path from the starting position to the food location. They reported the onset and offset of the imagined movements with a button press. Two main results emerged. First, imagery times were significantly longer for the thin than the large path. Second, participants liked significantly less the snack foods associated with the thin path (i.e., with longer imagery time), possibly because the passage of time strictly associated with action imagery discounts the value of the reward. Importantly, such effects were absent in a control group of participants who performed an identical valuation task, except that no action imagery was required. Our findings hint at the idea that imagined actions, like real actions, carry a cost that affects deeply how people assign value to the stimuli in their environment.

Dopamine modulating agents alter individual subdomains of motivation-related behavior assessed by touchscreen procedures.

Development of novel treatments for motivational deficits experienced by individuals with schizophrenia and major depressive disorder requires procedures that reliably assess effort-related behavior in pre-clinical models. High-throughput touchscreen-based testing, that parallels the computerized assessment of human patients, offers a platform for the establishment of tasks with high level of translational validity. Considerable efforts have been made to validate the touchscreen version of tasks that measure the degree of effort an animal is willing to invest for a reward, such as progressive ratio task. While motivational studies primarily focus on reporting alterations of a breakpoint, touchscreen assessment allows to collect multiple measures, especially if additional tasks would be adapted to the touchscreen environment. Classifying these measures to distinct behavioral subdomains is necessary for an evaluation of pre-clinical models. Here we apply data-driven classification techniques to identify behavioral clusters from dataset obtained in progressive ratio task and a novel effort-related choice task that we established and validated in the touchscreen boxes. Moreover, we measure the effect of pharmacological manipulations of the level of dopamine, a key regulator of reward- and effort-related processing, on individual behavioral subdomains that describe effort-related activity, non-specific activity, locomotion, and effort-related choice. Our approach expands the touchscreen-based assessment of pre-clinical models of motivational symptoms, identifies the most relevant behavioral measures in assessing the degree of reward-driven effort and contributes to the understanding of the role of dopamine in mediating distinct aspects of effort-related motivation.

Cognitive effort exertion enhances electrophysiological responses to rewarding outcomes.

Recent work has highlighted neural mechanisms underlying cognitive effort-related discounting of anticipated rewards. However, findings on whether effort exertion alters the subjective value of obtained rewards are inconsistent. Here, we provide a more nuanced account of how cognitive effort affects subsequent reward processing in a novel task designed to assess effort-induced modulations of the Reward Positivity, an event-related potential indexing reward-related neural activity. We found that neural responses to both gains and losses were significantly elevated in trials requiring more versus less cognitive effort. Moreover, time-frequency analysis revealed that these effects were mirrored in gain-related delta, but not in loss-related theta band activity, suggesting that people ascribed more value to high-effort outcomes. In addition, we also explored whether individual differences in behavioral effort discounting rates and reward sensitivity in the absence of effort may affect the relationship between effort exertion and subsequent reward processing. Together, our findings provide evidence that cognitive effort exertion can increase the subjective value of subsequent outcomes and that this effect may primarily rely on modulations of delta band activity.

Associations Between Negative Symptoms and Effort Discounting in Patients With Schizophrenia and Major Depressive Disorder.

Deficits in goal-directed decision making and motivation are hallmark characteristics of several neuropsychiatric disorders, including schizophrenia (SZ) and major depressive disorder (MDD). Studies using effort-based decision-making tasks have shown that both patients with SZ and MDD invest less physical effort in order to obtain rewards. However, how these motivational deficits relate to clinically assessed symptom dimensions such as apathy remains controversial. Using a grip-strength-based effort discounting task we assessed effort-based decision-making behavior in healthy controls (HC) (N = 18), patients with SZ (N = 42), and MDD (N = 44). We then investigated how effort discounting relates to different symptom dimensions. There were no differences in effort discounting between HC participants and patients with SZ or MDD. In addition, we did not observe a correlation between effort discounting and negative symptoms (NS) in patients with SZ or MDD. In conclusion, the current study does not support an association between effort discounting and NS in SZ or MDD. Further studies are needed to investigate effort discounting and its relation to psychopathological dimensions across different neuropsychiatric disorders.

Gain-loss asymmetry in delay and effort discounting of different amounts.

Loss aversion entails that people attribute greater weight to losses than to equivalent gains. In terms of discounting, it is reflected in a higher discounting rate for gains than for losses. Research on delay discounting indicates that such gain-loss asymmetry may depend on the amount of the outcome being considered. Consequently, here we address the question of how gains and losses are discounted in delay or effort conditions (physical or cognitive) across four outcome amounts. Our results replicate previous findings for intertemporal choices by showing that losses are discounted more slowly than gains, but only for smaller amounts-with no evidence of an asymmetrical evaluation for larger amounts. In physical effort discounting, we found an inverse asymmetry for the smallest amount tested (gains are discounted less steeply than losses). However, this effect was absent for larger amounts. We found no evidence to support a gain-loss asymmetry in the evaluation of gains or losses in cognitive effort. Overall, our findings indicate that loss aversion may not be as pervasive as previously expected, at least when decisions are effort-based.

Effects of effort training on effort-based impulsive choice.

Because impulsive decision-making is correlated with many maladaptive tendencies, researchers have increasingly studied methods for reducing impulsive choice. These efforts have primarily focused on increasing choices of larger, more-delayed rewards. A second type of impulsive choice is selecting a smaller, less-effortful reward over a larger, more-effortful one. Little nonhuman research has examined experimental methods for reducing effort-based impulsive choice. Within the realm of delay-based impulsive choice, extended exposure to reinforcer delays has proven effective in reducing impulsive choices in rats. The current study took a similar tack by evaluating if reductions in effort-based impulsive choice could be achieved by providing rats with extended exposure to high-effort training, that is, reinforcement contingencies requiring a large number of responses. Male rats were randomly assigned to either a high-effort training (fixed-ratio 50) or low-effort training (fixed-ratio 1) group. Following training, both groups completed a test of effort-based impulsive choice. High-effort training produced a temporary reduction in effort-based impulsive choice. In the same test phase, groups also differed in response run durations (shorter following high-effort training), with larger differences in the initial sessions, which may have contributed to the short-term effect of high-effort training in effort-based impulsive choice.

Dispositional individual differences in cognitive effort investment: establishing the core construct.

BACKGROUND: Individuals tend to avoid effortful tasks, regardless of whether they are physical or mental in nature. Recent experimental evidence is suggestive of individual differences in the dispositional willingness to invest cognitive effort in goal-directed behavior. The traits need for cognition (NFC) and self-control are related to behavioral measures of cognitive effort discounting and demand avoidance, respectively. Given that these traits are only moderately related, the question arises whether they reflect a common core factor underlying cognitive effort investment. If so, the common core of both traits might be related to behavioral measures of effort discounting in a more systematic fashion. To address this question, we aimed at specifying a core construct of cognitive effort investment that reflects dispositional differences in the willingness and tendency to exert effortful control. METHODS: We conducted two studies (N = 613 and N = 244) with questionnaires related to cognitive motivation and effort investment including assessment of NFC, intellect, self-control and effortful control. We first calculated Pearson correlations followed by two mediation models regarding intellect and its separate aspects, seek and conquer, as mediators. Next, we performed a confirmatory factor analysis of a hierarchical model of cognitive effort investment as second-order latent variable. First-order latent variables were cognitive motivation reflecting NFC and intellect, and effortful self-control reflecting self-control and effortful control. Finally, we calculated Pearson correlations between factor scores of the latent variables and general self-efficacy as well as traits of the Five Factor Model of Personality for validation purposes. RESULTS: Our findings support the hypothesized correlations between the assessed traits, where the relationship of NFC and self-control is specifically mediated via goal-directedness. We established and replicated a hierarchical factor model of cognitive motivation and effortful self-control that explains the shared variance of the first-order factors by a second-order factor of cognitive effort investment. CONCLUSIONS: Taken together, our results integrate disparate literatures on cognitive motivation and self-control and provide a basis for further experimental research on the role of dispositional individual differences in goal-directed behavior and cost-benefit-models.

Dissociable Motivational Deficits in Pre-manifest Huntington's Disease.

Motivation is characterized by a willingness to overcome both cognitive and physical effort costs. Impairments in motivation are common in striatal disorders, such as Huntington's disease (HD), but whether these impairments are isolated to particular domains of behavior is controversial. We ask whether HD differentially affects the willingness of individuals to overcome cognitive versus physical effort. We tested 20 individuals with pre-manifest HD and compared their behavior to 20 controls. Across separate trials, participants made choices about how much cognitive or physical effort they were willing to invest for reward. Our key results were that individuals with pre-manifest HD were less willing than controls to invest cognitive effort but were no different in their overall preference for physical effort. These results cannot be explained by group differences in neuropsychological or psychiatric profiles. This dissociation of cognitive- and physical-effort-based decisions provides important evidence for separable, domain-specific mechanisms of motivation.

Losses Motivate Cognitive Effort More Than Gains in Effort-Based Decision Making and Performance.

Human behavior is more strongly driven by the motivation to avoid losses than to pursue gains (loss aversion). However, there is little research on how losses influence the motivation to exert effort. We compared the effects of loss and gain incentives on cognitive task performance and effort-based decision making. In three experiments, participants performed a cognitively effortful task under gain and loss conditions and made choices about effort expenditure in a decision-making task. Results consistently showed significant loss aversion in effort-based decision making. Participants were willing to invest more effort in the loss compared to the gain condition (i.e., perform a longer duration task: Experiments 1 and 2; or higher task load: Experiment 3). On the other hand, losses did not lead to improved performance (sustained attention), or higher physiological effort (pupil diameter) in Experiments 1 and 2. In Experiment 3, losses did enhance working memory performance, but only at the highest load level. Taken together, these results suggest that loss aversion motivates higher effort investment in effort-based decision-making, while the effect of loss aversion during a performance may depend on the task type or effort level.

Causal role of lateral prefrontal cortex in mental effort and fatigue.

Dorsolateral prefrontal cortex (DLPFC) is well-known for its role in exerting mental work, however the contribution of DLPFC for deciding whether or not to engage in effort remains unknown. Here, we assessed the causal role of DLPFC in effort-based decision making. We disrupted functioning of DLPFC with noninvasive brain stimulation before participants repeatedly decided whether to exert mental effort in a working memory task. We found the same DLPFC subregion involved in mental effort exertion to influence also effort-based decisions: First, it enhanced effort discounting, suggesting that DLPFC may signal the capacity to successfully deal with effort demands. Second, a novel computational model integrating the costs of enduring effort into the effort-based decision process revealed that DLPFC disruption reduced fatigue after accumulated effort exertion, linking DLPFC activation with fatigue. Together, our findings indicate that in effort-based decisions DLPFC represents the capacity to exert mental effort and the updating of this information with enduring time-on-task, informing theoretical accounts on the role of DLPFC in the motivation to exert mental effort and the fatigue arising from it.