Arms, bending discounting functions: how motor actions affect intertemporal decision-making (original) (raw)
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Analysis of hand kinematics reveals inter‑individual differences in intertemporal decision dynamics
During intertemporal decisions, the preference for smaller, sooner reward over larger-delayed rewards (temporal discounting, TD) exhibits substantial inter-subject variability; however, it is currently unclear what are the mechanisms underlying this apparently idiosyncratic behavior. To answer this question, here we recorded and analyzed mouse movement kinematics during intertemporal choices in a large sample of participants (N = 86). Results revealed a specific pattern of decision dynamics associated with the selection of “immediate” versus “delayed” response alternatives, which well discriminated between a “discounter” versus a “farsighted” behavior—thus representing a reliable behavioral marker of TD preferences. By fitting the Drift Diffusion Model to the data, we showed that differences between discounter and farsighted subjects could be explained in terms of different model parameterizations, corresponding to the use of different choice mechanisms in the two groups. While farsighted subjects were biased toward the “delayed” option, discounter subjects were not correspondingly biased toward the “immediate” option. Rather, as shown by the dynamics of evidence accumulation over time, their behavior was characterized by high choice uncertainty.
eneuro, 2021
It is widely assumed that we select actions we value the most. While the influence of rewards on decisionmaking has been extensively studied, evidence regarding the influence of motor costs is scarce. Specifically, how and when motor costs are integrated in the decision process is unclear. Twenty-two right-handed human participants performed a reward-based target selection task by reaching with their right arm toward one of two visual targets. Targets were positioned in different directions according to biomechanical preference, such that one target was systematically associated with a lower motor cost than the other. Only one of the two targets was rewarded, either in a congruent or incongruent manner with respect to the associated motor cost. A timed-response paradigm was used to manipulate participants' reaction times (RT). Results showed that when the rewarded target carried the highest motor cost, movements produced at short RT (,350 ms) were deviated toward the other (i.e., non-rewarded, low-cost (LC) target). In this context participants needed an additional 150-ms delay to reach the same percentage of rewarded trials as when the LC target was rewarded. Crucially, motor costs affected the total earnings of participants. These results demonstrate a robust interference of motor costs in a simple reward-based decision-making task. They point to the rapid and automatic integration of motor costs at an early stage of processing, potentially through the direct modulation of competing action representations in parieto-frontal regions. The progressive overcoming of this bias with increasing RT is likely achieved through top-down signaling pertaining to expected rewards.
Temporal discounting of reward and the cost of time in motor control
The Journal of Neuroscience, 2010
Why do movements take a characteristic amount of time, and why do diseases that affect the reward system alter control of movements? Suppose that the purpose of any movement is to position our body in a more rewarding state. People and other animals discount future reward as a hyperbolic function of time. Here, we show that across populations of people and monkeys there is a correlation between discounting of reward and control of movements. We consider saccadic eye movements and hypothesize that ...
Losing control: the hidden role of motor areas in decision-making
Decision-making has traditionally been viewed as detached from the neural systems of sensory perception and motor function. Consequently, motor areas have played a relatively minor role in discussions surrounding the control processes and neural origins of decision-making. Empiric evidence, catalysed by technological advances in the past two decades, has proven that motor areas have an integral role in decision-making. They are involved in the generation, modulation, maintenance and execution of decisions and actions. They also take part in a complex hierarchical assessment of multi-modal inputs to ensure that the most appropriate action is generated given the context presented. Clinical conditions such as, alien hand syndrome and utilisation behaviour exemplify the importance of these regulatory controls. This review charts the trajectory of our understanding of the hidden role of motor areas in decision-making and reflects upon the implications of our deepened understanding. The convergence of evidence from multiple modalities underpinning our current knowledge is discussed and the potential applications thereof considered.
Hasty sensorimotor decisions rely on an overlap of broad and selective changes in motor activity
PLOS Biology
Humans and other animals are able to adjust their speed–accuracy trade-off (SAT) at will depending on the urge to act, favoring either cautious or hasty decision policies in different contexts. An emerging view is that SAT regulation relies on influences exerting broad changes on the motor system, tuning its activity up globally when hastiness is at premium. The present study aimed to test this hypothesis. A total of 50 participants performed a task involving choices between left and right index fingers, in which incorrect choices led either to a high or to a low penalty in 2 contexts, inciting them to emphasize either cautious or hasty policies. We applied transcranial magnetic stimulation (TMS) on multiple motor representations, eliciting motor-evoked potentials (MEPs) in 9 finger and leg muscles. MEP amplitudes allowed us to probe activity changes in the corresponding finger and leg representations, while participants were deliberating about which index to choose. Our data indica...
Predicting Future Sensorimotor States Influences Current Temporal Decision Making
Journal of Neuroscience, 2011
Accurate motor execution is achieved by estimating future sensory states via a forward model of limb dynamics. In the current experiment, we probed the time course over which state estimation evolves during movement planning by combining a bimanual arm crossing movement with a temporal order judgment (TOJ) task. Human participants judged which of two successive vibrotactile stimuli delivered to each index finger arrived first as they were preparing to either cross or uncross their hands. TOJ error rate was found to systematically vary in a time-and direction-dependent manner. When planning to cross the hands, error rate systematically increased as the vibrotactile stimuli were delivered closer in time to the onset of the movement. By contrast, planning to uncross the hands led to a gradual reduction in error rate as movement planning progressed. In both cases, these changes occurred before the actual alteration in hand configuration. We suggest that these systematic changes in error represent an interaction between the evolving state estimation processes and decisions regarding the timing of successive events.
Motor Effort Alters Changes of Mind in Sensorimotor Decision Making
PLoS ONE, 2014
After committing to an action, a decision-maker can change their mind to revise the action. Such changes of mind can even occur when the stream of information that led to the action is curtailed at movement onset. This is explained by the time delays in sensory processing and motor planning which lead to a component at the end of the sensory stream that can only be processed after initiation. Such post-initiation processing can explain the pattern of changes of mind by asserting an accumulation of additional evidence to a criterion level, termed change-of-mind bound. Here we test the hypothesis that physical effort associated with the movement required to change one's mind affects the level of the change-of-mind bound and the time for post-initiation deliberation. We varied the effort required to change from one choice target to another in a reaching movement by varying the geometry of the choice targets or by applying a force field between the targets. We show that there is a reduction in the frequency of change of mind when the separation of the choice targets would require a larger excursion of the hand from the initial to the opposite choice. The reduction is best explained by an increase in the evidence required for changes of mind and a reduced time period of integration after the initial decision. Thus the criteria to revise an initial choice is sensitive to energetic costs.
Body dynamics of gait affect value-based decisions
Scientific Reports, 2021
Choosing among different options typically entails weighing their anticipated costs and benefits. Previous research has predominantly focused on situations, where the costs and benefits of choices are known before an action is effectuated. Yet many decisions in daily life are made on the fly, for instance, making a snack choice while walking through the grocery store. Notably, the costs of actions change dynamically while moving. Therefore, in this study we examined whether the concurrent action dynamics of gait form part of and affect value-based decisions. In three experiments, participants had to decide which lateral (left vs. right) target (associated with different rewards) they would go to, while they were already walking. Results showed that the target choice was biased by the alternating stepping behavior, even at the expense of receiving less reward. These findings provide evidence that whole-body action dynamics affect value-based decisions. Imagine yourself walking through the grocery store. While walking down the aisle in the candy section, you start having an appetite for candy. To your left you see your favorite liquorice. Somewhat closer to your right you see your favorite fruit gums. Which snack will you go for? Value-based decision-making is often considered to be a cognitive weighing process between costs and benefits 1,2. In this scenario, the benefit would perhaps be reflected by the caloric intake or tastiness of either of the two snacks, and the costs might include the cost of the action itself, here the physical effort it may take to walk to the liquorice, which is farther away than the fruit gums. There is empirical evidence supporting the claim that the costs of action play a significant role in decision-making 3-7. However, the majority of this research investigates just a snapshot of human decisions, namely situations in which choices and actions can be implemented sequentially. Per definition, in sequential decisions, cost and reward information is available before an action is initiated. Only after weighing the options, the action is executed. Theories of sequential decision-making such as good-based models 8 and evidence accumulation models 9 assume that costs and rewards are being weighted independently of actions. Good-based models focus on where the competition between action choices occurs 8,11. They assume that the comparison of choice options takes place at an abstract level independent of sensorimotor representations. As such, decision and action are separate, sequentially unfolding modules. Only after reaching a decision boundary modeled as competition between abstract choice options, the decision is accomplished and implemented by a respective sensorimotor action. Evidence accumulation models focus on a formal specification of how selection occurs 9,11. More specifically, evidence is sampled in a sequential manner until one choice option reaches a threshold. Similar to good-based models, only afterwards an action is initiated. It follows that in these theories the flow of information is modeled in a unidirectional manner: the choice governs the action 8,9. According to Lepora and Pezzulo 10 , when a decision is made and only afterwards an action is initiated, by definition the action dynamics-evolving a posteriori-cannot influence the already made decision without feedback from action dynamics. Consequently, sequential decision-making theories 8,9 cannot account for many situations in which decisions have to be made during action execution, be it in sports (e.g., when deciding whether to pass a defender on the left or right while dribbling the ball), work environments (e.g., when navigating through a construction site), or other everyday situations (e.g., when making a snack choice while walking). In such situations costs of actions change dynamically and hence may need to be continuously updated and integrated into the decision process, a process not covered by sequential decision-making models. Therefore, alternative theoretical approaches have been proposed, including the embodied choice framework 10 and action-based models 11-13. These approaches do integrate dynamic action costs in decision-making. The embodied choice framework assumes bidirectional, continuous feedback between the action and the decision process 10. This entails feedback about dynamic action costs that are continuously fed back into the decision. Action-based models propose that the degree of activation between competing actions reflects the weighing of costs and rewards, thereby arguing that action and decision processes form an inseparable unity 11-13 .
PLoS biology, 2017
When deciding between alternative options, a rational agent chooses on the basis of the desirability of each outcome, including associated costs. As different options typically result in different actions, the effort associated with each action is an essential cost parameter. How do humans discount physical effort when deciding between movements? We used an action-selection task to characterize how subjective effort depends on the parameters of arm transport movements and controlled for potential confounding factors such as delay discounting and performance. First, by repeatedly asking subjects to choose between 2 arm movements of different amplitudes or durations, performed against different levels of force, we identified parameter combinations that subjects experienced as identical in effort (isoeffort curves). Movements with a long duration were judged more effortful than short-duration movements against the same force, while movement amplitudes did not influence effort. Biomecha...