Effort Exertion Research Articles

Non-invasive vagus nerve stimulation boosts mood recovery after effort exertion.

Mood plays an important role in our life which is illustrated by the disruptive impact of aberrant mood states in depression. Although vagus nerve stimulation (VNS) has been shown to improve symptoms of depression, the exact mechanism is still elusive, and it is an open question whether non-invasive VNS could be used to swiftly and robustly improve mood. Here, we investigated the effect of left- and right-sided transcutaneous auricular VNS (taVNS) v. a sham control condition on mood after the exertion of physical and cognitive effort in 82 healthy participants (randomized cross-over design) using linear mixed-effects and hierarchical Bayesian analyses of mood ratings. We found that 90 min of either left-sided or right-sided taVNS improved positive mood [b = 5.11, 95% credible interval, CI (1.39-9.01), 9.6% improvement relative to the mood intercept, BF10 = 7.69, pLME = 0.017], yet only during the post-stimulation phase. Moreover, lower baseline scores of positive mood were associated with greater taVNS-induced improvements in motivation [r = -0.42, 95% CI (-0.58 to -0.21), BF10 = 249]. We conclude that taVNS boosts mood after a prolonged period of effort exertion with concurrent stimulation and that acute motivational effects of taVNS are partly dependent on initial mood states. Collectively, our results show that taVNS may help quickly improve affect after a mood challenge, potentially by modulating interoceptive signals contributing to the reappraisal of effortful behavior. This suggests that taVNS could be a useful add-on to current behavioral therapies.

How adolescents and adults translate motivational value to action: Age-related shifts in strategic physical effort exertion for monetary rewards.

Adults titrate the degree of physical effort they are willing to expend according to the magnitude of reward they expect to obtain, a process guided by incentive motivation. However, it remains unclear whether adolescents, who are undergoing normative developmental changes in cognitive and reward processing, translate incentive motivation into action in a way that is similarly tuned to reward value and economical in effort utilization. The present study adapted a classic physical effort paradigm to quantify age-related changes in motivation-based and strategic markers of effort exertion for monetary rewards from adolescence to early adulthood. One hundred three participants aged 12-23 years completed a task that involved exerting low or high amounts of physical effort, in the form of a hand grip, to earn low or high amounts of money. Adolescents and young adults exhibited highly similar incentive-modulated effort for reward according to measures of peak grip force and speed, suggesting that motivation for monetary reward is consistent across age. However, young adults expended energy more economically and strategically: Whereas adolescents were prone to exert excess physical effort beyond what was required to earn reward, young adults were more likely to strategically prepare before each grip phase and conserve energy by opting out of low reward trials. This work extends theoretical models of development of incentive-driven behavior by demonstrating that layered on similarity in motivational value for monetary reward, there are important differences in the way behavior is flexibly adjusted in the presence of reward from adolescence to young adulthood. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Design of Sliding Mode Observer Based Controller of Single-Phase Induction Motor

Single-phase induction motors are simple in construction, cheap in cost, reliable and easy to repair and maintain. Many controllers were designed to control the speed of a single-phase induction motor, but they are sensitive to plant parameter variations and disturbances. Speed control with very less transient response requires non-linear and robust control methods. Sliding mode control is one of the robust control techniques which is insensitive to disturbances. Here we propose a higher order sliding mode (SM) observer-based controller for a single-phase induction motor. The applied control depends on the dynamic model of the induction motor. The controller is structured by applying a blend of input linearization strategy and higher order sliding mode calculation with consistent estimation of rotor speed and stator currents, which limits the vulnerabilities continuously and lessen the chattering phenomenon in the control effort exertion utilizing a super twisting algorithm.

Task-evoked pupillary responses track effort exertion: Evidence from task-switching.

A spate of research has examined how individuals regulate effortful processing in service of goal-directed behaviors. One key challenge in developing an account of this regulation is quantifying the momentary amount of cognitive effort exerted by an individual in service of their goals. A growing body of literature has suggested using task-evoked pupil dilations as a potential psychophysiological index of cognitive effort; however, it remains unclear whether pupil diameter indexes effort exertion or merely reflects task load, as both are tightly intertwined. Here, we attempt to disentangle these disparate accounts of pupil diameter by leveraging individual differences in executive function (as measured by Stroop interference) and a motivational manipulation (i.e., monetary incentives) while participants complete a task-switching paradigm. In line with both the effort and demand accounts, we observed larger task-evoked pupillary responses (TEPRs) for trials in which there was a task switch versus a task repetition. Additionally, we found that larger phasic pupillary responses at baseline (without reward incentives) predicted smaller switch costs. Mirroring this pattern, individual differences in reward-induced switch cost reductions were predicted by reward-induced increases in phasic pupil diameter. Finally, we observed that the interrelationship between effort and pupil diameter at baseline was modulated by individual differences in Stroop interference costs. Together, these findings provide support for an effort account of TEPRs, and suggest that pupillometry is a viable index of cognitive effort.

Effort exertion and contract design in collaborative product development with fairness concern

Purpose This study aims to model collaborative product development (CPD) among a focal firm (FF) and a fairness-concerned external partner (EP). The model is used to explore the impact of fairness concerns on revenue distributing contract and innovation efforts. The study also examines the role of follow-up sales in product development decisions. Design/methodology/approach A sequential game-theoretic model is developed to analyze product development decisions between the two parties, where participants exert innovation efforts to promote the product value and a revenue-sharing contract is used to distribute the revenue. Findings Fairness concern of EP has significant impacts on decisions. FF has incentives to change the contract in that fairness concerns might decrease his profit. Conditions and results change when the contract is endogenously decided. First, FF tends to develop the product independently. Second, FF may share a smaller revenue fraction with EP, as FF relies more on his own efforts during CPD. Third, FF cannot benefit from fairness concerns, as his profit is not higher than that in the benchmark. Finally, the existence of follow-up sales does not change FF’s decision about whether to collaborate with EP. Originality/value This study incorporates fairness preference into CPD decisions. Besides, a new concept of fairness called “effort-related fairness” is proposed.

Agency problems in public-private partnerships investment projects

This paper examines concession contracts between a private firm and a government in the presence of moral hazard within a real-options framework. The design of optimal contracts to provide incentives to the private firm to exert effort is analyzed. We show that although first-best investment timing can be implemented, contracts often do not provide firms with proper incentives to exert effort, resulting in high-cost projects being undertaken. This problem can be alleviated through the use of a monitoring technology that imposes a penalty on the shirking firm. Although monitoring distorts the investment timing leading to a delayed investment, it increases the government’s profits at the expense of the firm, so that the government finds it optimal to induce effort exertion, increasing the likelihood of low-cost projects. Considering jointly incentives and an exit option, we show that the regular compensation of firms and their compensation upon termination act as substitutes in providing incentives. Governments should set these remunerations jointly in order to minimize the cost of a bailout option for the society.

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.

Chemogenetic Modulation and Single-Photon Calcium Imaging in Anterior Cingulate Cortex Reveal a Mechanism for Effort-Based Decisions.

The ACC is implicated in effort exertion and choices based on effort cost, but it is still unclear how it mediates this cost-benefit evaluation. Here, male rats were trained to exert effort for a high-value reward (sucrose pellets) in a progressive ratio lever-pressing task. Trained rats were then tested in two conditions: a no-choice condition where lever-pressing for sucrose was the only available food option, and a choice condition where a low-value reward (lab chow) was freely available as an alternative to pressing for sucrose. Disruption of ACC, via either chemogenetic inhibition or excitation, reduced lever-pressing in the choice, but not in the no-choice, condition. We next looked for value coding cells in ACC during effortful behavior and reward consumption phases during choice and no-choice conditions. For this, we used in vivo miniaturized fluorescence microscopy to reliably track responses of the same cells and compare how ACC neurons respond during the same effortful behavior where there was a choice versus when there was no-choice. We found that lever-press and sucrose-evoked responses were significantly weaker during choice compared with no-choice sessions, which may have rendered them more susceptible to chemogenetic disruption. Together, findings from our interference experiments and neural recordings suggest that a mechanism by which ACC mediates effortful decisions is in the discrimination of the utility of available options. ACC regulates these choices by providing a stable population code for the relative value of different options.SIGNIFICANCE STATEMENT The ACC is implicated in effort-based decision-making. Here, we used chemogenetics and in vivo calcium imaging to explore its mechanism. Rats were trained to lever press for a high-value reward and tested in two conditions: a no-choice condition where lever-pressing for the high-value reward was the only option, and a choice condition where a low-value reward was also available. Inhibition or excitation of ACC reduced effort toward the high-value option, but only in the choice condition. Neural responses in ACC were weaker in the choice compared with the no-choice condition. A mechanism by which ACC regulates effortful decisions is in providing a stable population code for the discrimination of the utility of available options.

Supplemental Material for How Adolescents and Adults Translate Motivational Value to Action: Age-Related Shifts in Strategic Physical Effort Exertion for Monetary Rewards

Supplemental Material for How Adolescents and Adults Translate Motivational Value to Action: Age-Related Shifts in Strategic Physical Effort Exertion for Monetary Rewards

Pupillary change on a cognitive effort task in schizophrenia: Associations with cognition and motivation

Motivational negative symptoms in schizophrenia are associated with abnormalities in effort allocation. Pupillary dilation is a reliable biomarker of effort allocation and was used in this study to evaluate the associations between cognitive effort, ability, and motivation. Individuals with schizophrenia/schizoaffective disorder and moderate-to-high negative symptoms were assessed with pupillometry while performing a cognitive effort task that manipulated level of cognitive difficulty. Participants were also assessed with measures of ability (i.e., cognition and functional capacity), and motivation (i.e., defeatist beliefs and motivational negative symptoms). Pupillary change was examined as an effort modulation index in relation to the ability and motivation measures. Greater pupillary change (i.e., exerting greater amounts of effort) on the hard versus easy conditions was correlated with better cognition and functional capacity and lower motivational negative symptoms, while defeatist beliefs were not significantly correlated. In hierarchical regression analyses, ability measures were entered first and motivation measures were entered second. Motivation measures predicted variance beyond ability. Our findings indicate that both ability and motivation are significant determinants of pupillary indicators of cognitive effort exertion. Further, the results highlight the importance of controlling for cognition when using pupil dilation to index effort/motivation.

Strong Effort Manipulations Reduce Response Caution: A Preregistered Reinvention of the Ego-Depletion Paradigm

People feel tired or depleted after exerting mental effort. But even preregistered studies often fail to find effects of exerting effort on behavioral performance in the laboratory or elucidate the underlying psychology. We tested a new paradigm in four preregistered within-subjects studies (N = 686). An initial high-demand task reliably elicited very strong effort phenomenology compared with a low-demand task. Afterward, participants completed a Stroop task. We used drift-diffusion modeling to obtain the boundary (response caution) and drift-rate (information-processing speed) parameters. Bayesian analyses indicated that the high-demand manipulation reduced boundary but not drift rate. Increased effort sensations further predicted reduced boundary. However, our demand manipulation did not affect subsequent inhibition, as assessed with traditional Stroop behavioral measures and additional diffusion-model analyses for conflict tasks. Thus, effort exertion reduced response caution rather than inhibitory control, suggesting that after exerting effort, people disengage and become uninterested in exerting further effort.

The Effects of Psychosocial Stress and Sex Differences on Cognitive Effort Avoidance

Background: Recent research suggests stress may affect cognitive performance including memory, executive functioning, decision-making, and task-switching. However, it is unknown whether these effects are aversive or advantageous for effort exertion. This experiment aimed to evaluate the effects of acute psychosocial stress on willingness to exert cognitive control processes in a cognitive-effort-based decision-making task.Methods: To test this, 40 participants (20 female) in a within-subject, fully crossed, randomized design, were exposed to both a psychosocial stress induction condition (the Trier Social Stress Test; TSST) and a control condition. Subsequently, they underwent the Demand Selection Task (DST) that tests for participants’ effort aversion by manipulating switch probabilities in a task-switching paradigm. Results and Conclusion: The induction of stress did not lead to significant error or accuracy rates, or significant differences in cognitive effort avoidance. Previous research indicated sex differences in response to stress. However, there is a lack of data on sex differences in the avoidance of demanding cognitive processes. Therefore, we assessed sex differences in the DST and found that women were more likely to avoid cognitive effort, choosing the less cognitively demanding cue more often than men. Limitations: A limitation of this study is the small sample size. Future research should increase the sample size and take individual differences in stress responders, type of stressor, and biases on effort exertion into account.

Modeling Dynamic Allocation of Effort in a Sequential Task Using Discounting Models.

Most rewards in our lives require effort to obtain them. It is known that effort is seen by humans as carrying an intrinsic disutility which devalues the obtainable reward. Established models for effort discounting account for this by using participant-specific discounting parameters inferred from experiments. These parameters offer only a static glance into the bigger picture of effort exertion. The mechanism underlying the dynamic changes in a participant's willingness to exert effort is still unclear and an active topic of research. Here, we modeled dynamic effort exertion as a consequence of effort- and probability-discounting mechanisms during goal reaching, sequential behavior. To do this, we developed a novel sequential decision-making task in which participants made binary choices to reach a minimum number of points. Importantly, the time points and circumstances of effort allocation were decided by participants according to their own preferences and not imposed directly by the task. Using the computational model to analyze participants' choices, we show that the dynamics of effort exertion arise from a combination of changing task needs and forward planning. In other words, the interplay between a participant's inferred discounting parameters is sufficient to explain the dynamic allocation of effort during goal reaching. Using formal model comparison, we also inferred the forward-planning strategy used by participants. The model allowed us to characterize a participant's effort exertion in terms of only a few parameters. Moreover, the model can be adapted to a number of tasks used in establishing the neural underpinnings of forward-planning behavior and meta-control, allowing for the characterization of behavior in terms of model parameters.

Distinguishing cognitive effort and working memory load using scale-invariance and alpha suppression in EEG

Despite being intuitive, cognitive effort has proven difficult to define quantitatively. Here, we proposed to study cognitive effort by investigating the degree to which the brain deviates from its default state, where brain activity is scale-invariant. Specifically, we measured such deviations by examining changes in scale-invariance of brain activity as a function of task difficulty and posited suppression of scale-invariance as a proxy for exertion of cognitive effort. While there is some fMRI evidence supporting this proposition, EEG investigations on the matter are scant, despite the EEG signal being more suitable for analysis of scale invariance (i.e., having a much broader frequency range). In the current study we validated the correspondence between scale-invariance (H) of cortical activity recorded by EEG and task load during two working memory (WM) experiments with varying set sizes. Then, we used this neural signature to disentangle cognitive effort from the number of items stored in WM within participants. Our results showed monotonic decreases in H with increased set size, even after set size exceeded WM capacity. This behavior of H contrasted with behavioral performance and an oscillatory indicator of WM load (i.e., alpha-band desynchronization), both of which showed a plateau at difficulty levels surpassing WM capacity. This is the first reported evidence for the suppression of scale-invariance in EEG due to task difficulty, and our work suggests that H suppression may be used to quantify changes in cognitive effort even when working memory load is at maximum capacity.

Multiperiod Contracting and Salesperson Effort Profiles: The Optimality of “Hockey Stick,” “Giving Up,” and “Resting on Laurels”

The authors study multiperiod sales force incentive contracting in which salespeople can engage in effort gaming, a phenomenon that has extensive empirical support. Focusing on a repeated moral hazard scenario with two independent periods and a risk-neutral agent with limited liability, the authors conduct a theoretical investigation to understand which effort profiles the firm can expect under the optimal contract. The authors show that various effort profiles that may give the appearance of being suboptimal, such as postponing effort exertion (“hockey stick”) and not exerting effort after a bad or a good initial demand outcome (“giving up” and “resting on laurels,” respectively) may indeed be induced optimally by the firm. This is because, under certain conditions that depend on how severe the contracting frictions are and how effective effort exertion is in increasing demand, the firm wants to concentrate rewards on extreme demand outcomes. Doing this induces gaming and reduces expected demand but also makes motivating effort cheaper, thus saving on incentive payments. On introducing dependence between time periods, such as when the agent can transfer demands between periods, this insight continues to hold and, furthermore, “hockey stick,” “giving up,” and “resting on laurels” can be optimal for the firm even under repeated short time horizon contracting. The results imply that one must carefully consider the setting and environmental factors when making inferences about contract effectiveness from dynamic effort profiles of agents.

Slow response times undermine trust in algorithmic (but not human) predictions

Algorithms consistently perform well on various prediction tasks, but people often mistrust their advice. Here, we demonstrate one component that affects people’s trust in algorithmic predictions: response time. In seven studies (total N = 1928 with 14,184 observations), we find that people judge slowly generated predictions from algorithms as less accurate and they are less willing to rely on them. This effect reverses for human predictions, where slowly generated predictions are judged to be more accurate. In explaining this asymmetry, we find that slower response times signal the exertion of effort for both humans and algorithms. However, the relationship between perceived effort and prediction quality differs for humans and algorithms. For humans, prediction tasks are seen as difficult and observing effort is therefore positively correlated with the perceived quality of predictions. For algorithms, however, prediction tasks are seen as easy and effort is therefore uncorrelated to the quality of algorithmic predictions. These results underscore the complex processes and dynamics underlying people’s trust in algorithmic (and human) predictions and the cues that people use to evaluate their quality.

Dopamine D1 receptors in the medial orbitofrontal cortex support effort-related responding in rats

Rodent studies on effort-related responding provide a tool to analyze basal aspects of motivation and to model psychiatric motivational dysfunctions reflecting low exertion of effort or reduced behavioral activation. It turned out that dopamine (DA) signaling in brain areas such as nucleus accumbens are essential in regulating effort-related motivational function and could play a major role in motivational dysfunction in psychiatric disorders. Recent rodent studies revealed that the medial orbitofrontal cortex (mOFC) is another key component of the neural circuitry regulating effort-related motivational function. The mOFC receives prominent DA input, however, the behavioral role of mOFC DA signaling is unknown. Here, we investigated whether DA signaling in the mOFC supports effort-related responding in rats. Results demonstrate that an intra-mOFC D1 receptor blockade markedly reduced effort-related responding in a progressive ratio task. Notably, the magnitude of this effect was comparable to the one caused by a systemic DA depletion induced by the VMAT-2 inhibitor tetrabenazine or by a satiety-induced motivational downshift. Collectively, our data show for the first time that D1 receptor activity in the mOFC plays a critical role in high effort responding. These results support findings in humans pointing to a role of the mOFC in effort-related responding. It is well known that the mOFC becomes dysfunctional in depression and schizophrenia. Our data point to the possibility that reduced mOFC DA activity could contribute to effort-related motivational symptoms in these disorders and support the notion that the DA system may be a drug target to treat effort-related motivational symptoms.

Preference for Exercise vs. More Sedentary Reinforcers: Validation of an Animal Model of Tetrabenazine-Induced Anergia.

Physical activities can have intrinsic motivational or reinforcing properties. The choice to engage in voluntary physical activity is undertaken in relation to the selection of other alternatives, such as sedentary behaviors, drugs, or food intake. The mesolimbic dopamine (DA) system plays a critical role in behavioral activation or exertion of effort, and DA antagonism or depletion induces anergia in effort-based decision-making tasks. However, little is known about the neural mechanisms underlying the decision-making processes that establish preferences for sedentary vs. activity-based reinforcers. In the present work with male CD1 mice, we evaluated the effect of tetrabenazine (TBZ), a DA-depleting agent, on a three-choice T-maze task developed to assess preference between reinforcers with different behavioral activation requirements and sensory properties [i.e., a running wheel (RW) vs. sweet pellets or a neutral nonsocial odor]. We also studied the effects of TBZ on the forced swim test (FST), which measures climbing and swimming in a stressful setting, and on anxiety tests [dark-light (DL) box and elevated plus maze (EPM)]. In the three-choice task, TBZ reduced time running in the wheel but increased time spent consuming sucrose, thus indicating reduced activation but relatively intact sucrose reinforcement. The effect of TBZ was not mimicked by motivational manipulations that change the value of the reinforcers, such as making the RW aversive or harder to move, food-restricting the animals, inducing a binge-like eating pattern, or introducing social odors. In the FST, TBZ decreased time climbing (most active behavior) and increased immobility but did not affect anxiety in the DL or EPM. These results indicate that the three-choice T-maze task could be useful for assessing DA modulation of preferences for exercise based on activation and effort requirements, differentiating those effects from changes in preference produced by altering physical requirements, food restriction state, and stress during testing.

Redefining the relationship between effort and reward: Choice-execution model of effort-based decisions

Neuroscientific studies reliably demonstrate that rewards play a crucial role in guiding our choices when confronted with different effortful actions we could make. At the same time, psychological and economic research shows that effort we exert is not reliably predicted by the rewards we end up receiving. Why the mismatch between the two lines of evidence? Inspired by neuroscientific literature, we argue that value-based models of decision-making expose the complexity of the relationship between effort and reward, which changes between two crucial stages of the effort-based decision making process: Choice (i.e. action selection) and Execution (i.e. action execution involving actual effort exertion). To test this assumption, in the present study we set up two experiments (E1: N = 72, E2: N = 87), using a typical neuroscientific effort-based decision-making task. The findings of these experiments reveal that when making prospective choices, rewards do guide the level of effort people are prepared to exert, consistent with typical findings from Neuroscience. At a later stage, during execution of effortful actions, performance is determined by the actual amount of effort that needs to be exerted, consistent with psychological and behavioral economic research. We use the model we tested and the findings we generated to highlight critical new insights into effort-reward relationship, bringing different literatures together in the context of questions regarding what effort its, and the role that values play.

You seem tired, but so am I: Willpower theories and intention to provide support in romantic relationships

Although providing support in romantic relationships is important for the well-being of both partners, providing support can be effortful. People have varying implicit theories about the exertion of effort; limited willpower theorists believe that mental resources become exhausted with use, while nonlimited willpower theorists believe that exerting effort can even prepare you for future exertion. While limited willpower theorists are more likely to experience depletion and limitations themselves, they may also be more likely to perceive and empathize with the depletion and limitations of their romantic partners. We conducted a daily diary study ( N = 363; 1,429 observations) to examine how willpower theories relate to participants’ intentions to support their romantic partners in the evenings. We find that limited theorists report their partners as more tired (predicting more intention to support)—however, limited theorists also report more fatigue and lower mood themselves (predicting less intention to support). Overall, limited willpower beliefs were associated with less, not more, intent to support one’s partner for the rest of the evening. Even if limited willpower theories improve people’s abilities to perceive their partner’s fatigue, at the end of the day, they may not feel they have the mental resources to support their romantic partners.