Assessing the role of reward in task selection using a reward-based voluntary task switching paradigm

Task switching with probabilistic reward schemes

Previous research has shown that transitions in reward prospect influence (voluntary) task switching behavior. Specifically, an increase in reward prospect appears to enhance flexibility, as indicated by a higher voluntary switch rate (VSR), compared to situations where the reward prospect remains high. In contrast, when participants are randomly rewarded in the previous task, they tend to stick with this task, resulting in a lower VSR. The present study further explores the impact of probabilistic reward schemes on task switching. Two tasks were associated with distinct probabilities of receiving a reward for correct responses (high vs. low probability). This design allows for more refined predictions regarding VSR based on the results summarized above. In three experiments with voluntary and cued task switching, we observed that participants switched tasks less frequently when they were rewarded on the previous trial, regardless of whether the task had a high or low reward probability. This pattern suggests the use of a win-stay, lose-shift (WSLS) strategy, where participants are more likely to repeat their choice after receiving a reward. However, reward had no impact on switch costs. These results are discussed in the broader context of decision-making research, particularly in relation to strategies like WSLS and possibly different levels of cognitive processes affected by our manipulation and that of studies investigating transitions of reward prospect.

Curiosity overpowers cognitive effort avoidance tendencies

Curiosity has been described as a desire to learn new information, and previous studies have demonstrated that curiosity drives peoples' decision to invest resources (e.g., time or tokens) to find out answers. It is commonly assumed that curiosity should also prompt people to invest more effort until they attain unknown answers. However, experimental evidence is lacking on whether people would be willing to exert cognitive effort - in addition to time investments - to find out answers. In three pre-registered experiments, we first asked participants to rate a set of 20 trivia questions regarding their curiosity about knowing the answers. Subsequently, participants had to perform a set of random-dot kinematograms (RDKs) to view the answer to each trivia question. We varied the motion coherence of the RDKs as a proxy for cognitive effort demands and tested whether curiosity overpowers cognitive effort avoidance tendencies. Our results provide converging evidence that curiosity outweighs peoples' tendencies to avoid cognitive effort. That is, participants avoided high-effort RDKs if they were not curious about information and when the exertion of cognitive effort did not affect the attainment of information. However, if participants were curious about questions and if no alternative low-effort option was available, they were willing to employ cognitive effort to find out answers.

The role of uncertain reward in voluntary task-switching as revealed by pupillometry and gaze

Cognitive flexibility, the brain's ability to adjust to changes in the environment, is a critical component of executive functioning. Previous literature shows a robust relationship between reward dynamics and flexibility: flexibility is highest when reward changes, while flexibility decreases when reward remains stable. The purpose of this study was to examine the role of uncertain reward in a voluntary task switching paradigm on behavior, pupillometry, and eye gaze. We used pupil dilation as a neuropsychological correlate of arousal and accumulated fixations on a region (i.e. dwell time) to measure oculomotor attention capture. Results during the cue phase showed that pupil dilation under a deterministic, but not a stochastic reinforcement schedule tracked arousal from the magnitude of reward. In addition, dwell time was increased for the eventual choice and dwell-time was reduced under high reward. Taken together, results show that arousal and attentional capture by reward depends to some extent on reward certainty. Turning to reward outcome, pupil dilation was highest (and average dwell time was lowest) following Error feedback compared to correct rewarded feedback. Overall results show that uncertain reward cues may alter pupil-linked arousal and attention as compared to certain reward, highlighting the role of uncertainty as an important modulator affecting attention and reward processing in environments that demand cognitive flexibility.

The influence of reward and loss outcomes after free- and forced-tasks on voluntary task choice

In four experiments, we investigated the impact of outcomes and processing mode (free versus forced) on subsequent voluntary task-switching behavior. Participants freely chose between two tasks or were forced to perform one, and the feedback they received randomly varied after correct performance (reward or no-reward; loss or no-loss). In general, we reasoned that the most recently applied task goal is usually the most valued one, leading people to prefer task repetitions over switches. However, the task values might be additionally biased by previous outcomes and the previous processing mode. Indeed, negatively reinforcing tasks with no-reward or losses generally resulted in more subsequent switches. Additionally, participants demonstrated a stronger attachment to free- compared to forced-tasks, as indicated by more switches when the previous task was forced, suggesting that people generally value free over forced-choice task goals. Moreover, the reward manipulation had a greater influence on switching behavior following free- compared to forced-tasks in Exp. 1 and Exp. 3, suggesting a stronger emphasis on evaluating rewarding outcomes associated with free-task choices. However, this inflationary effect on task choice seemed to be limited to reward and situations where task choice and performance more strongly overlap. Specifically, there was no evidence that switching behavior was differentially influenced after free-and forced-task as a function of losses (Exp. 2) or reward when task choice and task performance were separated (Exp. 4). Overall, the results provide new insights into how the valuation of task goals based on choice freedom and outcome feedback can influence voluntary task choices.

Task performance errors and rewards affect voluntary task choices

Humans are remarkably flexible in adapting their behavior to current demands. It has been suggested that the decision which of multiple tasks to perform is based on a variety of factors pertaining to the rewards associated with each task as well as task performance (e.g., error rates associated with each task and/or error commission on the previous trial). However, further empirical investigation is needed to examine whether task performance still influences task choices if task choices are rewarded but task performance is not. Accordingly, we exposed participants to a novel reward-varying voluntary task switching paradigm where the reward for the performed task gradually decreased while the reward associated for the alternative task was unchanged. Importantly, we rewarded participants' task choices before participants performed the task to investigate the effect of rewards independent from task performance. We examined the effect of (i) reward, (ii) error rates associated with each of the two tasks, and (iii) error commission in the previous trial on voluntary task choices. As expected, we found that participants' task selection was influenced by reward differences between task choices. In addition, error rates associated with a task also influenced task selection, with participants requiring larger reward differences to switch to a task associated with relatively higher error rates, compared to switching to a task with relatively lower error rates. However, errors in n - 1 did not influence participants' probability to switch to the alternative task. These findings contribute to an ongoing discussion on the influence of task performance on task selection.

Reactive and proactive control processes in voluntary task choice

Deciding which task to perform when multiple tasks are available can be influenced by external influences in the environment. In the present study, we demonstrate that such external biases on task-choice behavior reflect reactive control adjustments instead of a failure in control to internally select a task goal. Specifically, in two experiments we delayed the onset of one of two task stimuli by a short (50 ms), medium (300 ms), or long (1,000 ms) stimulus-onset asynchrony (SOA) within blocks while also varying the relative frequencies of short versus long SOAs across blocks (i.e., short SOA frequent vs. long SOA frequent). Participants' task choices were increasingly biased towards selecting the task associated with the first stimulus with increasing SOAs. Critically, both experiments also revealed that the short-to-medium SOA bias was larger in blocks with more frequent long SOAs when participants had limited time to prepare for an upcoming trial. When time to select an upcoming task was extended in Experiment 2, this interaction was not significant, suggesting that the extent to which people rely on reactive control adjustments is additionally modulated by proactive control processes. Thus, the present findings also suggest that voluntary task choices are jointly guided by both proactive and reactive processes, which are likely to adjust the relative activation of different task goals in working memory.

Perceptual processing demands influence voluntary task choice

Previous studies have suggested that people are sensitive to anticipated cognitive processing demands when deciding which task to perform, but the influence of perceptual processing demands on voluntary task choice is still unclear. The present study tested whether voluntary task choice behavior may be influenced by unpredictable task-specific perceptual processing demands. Across four experiments using different voluntary task choice procedures, we randomly varied the perceptual discriminability of stimuli (easy vs. hard color discrimination) for one of the two tasks. We reasoned that people could only reactively adjust their task choice behavior to the unpredictable discriminability manipulation if they engaged in some perceptual processing before a task goal becomes sufficiently activated to select the task for further processing. The results confirmed this hypothesis: Task performance data demonstrated the presence of perceptual (discriminability effects) and cognitive (switch costs) processing demands. Participants' choice behavior was affected by both types of processing demands (as reflected in a task repetition bias and a bias to select the color task with easy compared to hard discriminations). Thus, the present findings indicate that both perceptual and cognitive processing demands influence voluntary task choice behavior. We propose that higher-level goal activations interact at least partially with early perceptual processes to influence task choice behavior, suggesting a locus of voluntary choices during or after the perceptual stage within the information-processing stream.

The subjective evaluation of task switch cues is related to voluntary task switching

Task switching refers to the effortful mental process of shifting attention between different tasks. While it is well-established that task switching usually comes with an objective performance cost, recent studies have shown that people also subjectively evaluate task switching as negative. An open question is whether this affective evaluation of task switching is also related to actual decision making. In this pre-registered study, we therefore examined whether individual differences in the negative evaluation of task switch cues are related to less voluntary task switching. To this end, participants first performed a cued task switching paradigm where abstract cues signaled task transitions (repetition or alternation). In a second phase, these transition cues were used as prime stimuli in an affective priming procedure to assess participants' affective evaluation of task switching. In a third phase, participants were allowed to freely choose whether to switch or repeat tasks. We found that a more negative evaluation of task switching cues was related to lower switch rates in the voluntary task switching phase. This finding supports neuroeconomic theories of value-based decision making which suggest that people use their subjective value of control to decide whether to engage in (different) tasks.

The self-organized task switching paradigm: Movement effort matters

The self-organized task switching paradigm enables to investigate the link between task performance and task selection in a voluntary task switching setting that benefits task switches over task repetitions. For example, waiting for a repetition-related stimulus onset denotes environmental costs, which are balanced with internal task-switch costs. Here we extent this research by asking whether movement effort also plays a crucial role for task selection. In detail, we investigate how motor-related consequences, i.e., increasing force for task repetitions, influence task-switching behavior. Participants voluntarily switched between a number (i.e., even or odd) or letter task (i.e., vowel or consonant) using a robot system for response execution. With consecutive task repetitions the robot system was harder to move to the response target as we systematically added a damping load. We found that switch rate correlated with cognitive switch costs (i.e., costs in: reaction time, r = -0.741, and error rate, r = -0.545), and motor repetition cost represented by movement-time increment, r = 0.414. Interestingly, switch rate also correlated with individual force maximum, r = -0.480. However, switch rate did not correlate with movement-impulse increment, r = -0.033. Stepwise multiple regression analyses across participants revealed that 66% of variance are explained including all predicting factors. Yet, only cognitive costs and individual force maximum reached significant importance in the regression model. Hence, we extended switch-rate analyses using linear regression on a within-subject level, and thus, keeping individual force maximum constant. We found about 84% of variance explained by motor and cognitive costs. Thereby, movement impulse predicted task selection more than reaction time and more than movement time. Thus, we demonstrated that both cognitive and motor consequences influence task-switch behavior. Furthermore, we showed that task selection is importantly modulated by motor effort related to individual motor skills.

The role of objective and subjective effort costs in voluntary task choice

Human beings tend to avoid effort, if a less effortful option is equally rewarding. However, and in sharp contrast to this claim, we repeatedly found that (a subset of) participants deliberately choose the more difficult of two tasks in a voluntary task switching (VTS) paradigm even though avoidance of the difficult task was allowed (Jurczyk et al., Motivation Science 5:295–313, 2019). In this study, we investigate to what extent the deliberate switch to the difficult task is determined by the actual objective or the subjective effort costs for the difficult task. In two experiments, participants (N = 100, each) first went through several blocks of voluntary task choices between an easy and a difficult task. After that, they worked through an effort discounting paradigm, EDT, (Westbrook et al., PLoS One 8(7):e68210, 2013) that required participants to make a series of iterative choices between re-doing a difficult task block for a fixed amount or an easy task block for a variable (lower) amount of money until the individual indifference point was reached. In Experiment 1, the EDT comprised the same tasks from the VTS, in Experiment 2, EDT used another set of easy vs. difficult tasks. Results showed that the voluntary switch to the difficult task was mostly predicted by the objective performance costs and only marginally be the subjective effort cost. The switch to the difficult task may thus be less irrational than originally thought and at its avoidance at least partially driven by economic considerations.

Scaling of the Parameters for Cost Balancing in Self-Organized Task Switching

Previous studies on voluntary task switching using the self-organized task switching paradigm suggest that task performance and task selection in multitasking are related. When deciding between two tasks, the stimulus associated with a task repetition occurred with a stimulus onset asynchrony (SOA) that continuously increased with the number of repetitions, while the stimulus associated with a task switch was immediately available. Thus, the waiting time for the repetition stimulus increased with number of consecutive task repetitions. Two main results were shown: first, switch costs and voluntary switch rates correlated negatively - the smaller the switch costs, the larger the switch rates. Second, participants switched tasks when switch costs and waiting time for the repetition stimulus were similar. In the present study, we varied the SOA that increased with number of task repetitions (SOA increment) and also varied the size of the switch costs by varying the intertrial interval. We examined which combination of SOA increment and switch costs maximizes participants' attempts to balance waiting time and switch costs in self-organized task switching. We found that small SOA increments allow for fine-grained adaptation and that participants can best balance their switch costs and waiting times in settings with medium switch costs and small SOA increments. In addition, correlational analyses indicate relations between individual switch costs and individual switch rates across participants.

Balancing cognitive and environmental constraints when deciding to switch tasks: Exploring self-reported task-selection strategies in self-organised multitasking

We investigated how people balance cognitive constraints (switch costs) against environmental constraints (stimulus availabilities) to optimise their voluntary task switching performance and explored individual differences in their switching behaviour. Specifically, in a self-organised task-switching environment, the stimulus needed for a task repetition was delayed by a stimulus-onset asynchrony (SOA) that increased with each consecutive repetition until a task switch reset the SOA. As predicted, participants switched tasks when the SOA in task switches approximately matched their individual switch costs and thus they optimised local task performance. Interestingly, self-reports (confirmed by behavioural switching patterns) revealed two individual strategies: some participants (N = 34) indicated to guide their task selection behaviour based on preplanned task sequences over several trials, whereas others (N = 42) indicated to primarily decide on a trial-by-trial basis whether to switch or to repeat tasks. Exploration of switching behaviour based on the two strategy groups revealed additional insights into how people achieved adaptive task selection behaviour in this task environment. Overall, the present findings suggest that individuals select tasks with the aim of improving task performance when dealing with multiple task requirements, but they differ in their preferred individual task selection strategies.

Striatal-frontal network activation during voluntary task selection under conditions of monetary reward

During voluntary task selection, a number of internal and external biases may guide such a choice. However, it is not well understood how reward influences task selection when multiple options are possible. To address this issue, we examined brain activation in a voluntary task-switching paradigm while participants underwent fMRI (n = 19). To reinforce the overall goal to choose the tasks randomly, participants were told of a large bonus that they would receive at the end of the experiment for making random task choices. We also examined how occasional, random rewards influenced both task performance and brain activation. We hypothesized that these transient rewards would increase the value of the just-performed task, and therefore bias participants to choose to repeat the same task on the subsequent trial. Contrary to expectations, transient reward had no consistent behavioral effect on subsequent task choice. Nevertheless, the receipt of such rewards did influence activation in brain regions associated with reward processing as well as those associated with goal-directed control. In addition, reward on a prior trial was found to influence activation during task choice on a subsequent trial, with greater activation in a number of executive function regions compared with no-reward trials. We posit that both the random presentation of transient rewards and the overall task bonus for random task choices together reinforced the goal to choose the tasks randomly, which in turn influenced activation in both reward-related regions and those regions involved in abstract goal processing.

Mental labour

Mental effort is an elementary notion in our folk psychology and a familiar fixture in everyday introspective experience. However, as an object of scientific study, mental effort has remained rather elusive. Cognitive psychology has provided some tools for understanding how effort impacts performance, by linking effort with cognitive control function. What has remained less clear are the principles that govern the allocation of mental effort. Under what circumstances do people choose to invest mental effort, and when do they decline to do so? And what regulates the intensity of mental effort when it is applied? In new and promising work, these questions are being approached with the tools of behavioural economics. Though still in its infancy, this economic approach to mental effort research has already uncovered important aspects of effort-based decision-making, and points clearly to future lines of inquiry, including some intriguing opportunities presented by recent artificial intelligence research.