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

Dreisbach, Gesine; Jurczyk, Vanessa · 2021 · OpenAlex-citations

DOI: 10.1007/s00426-021-01587-2

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Summary

This study investigates the determinants of voluntary task switching (VTS), specifically addressing why a subset of participants deliberately choose more difficult tasks despite the general psychological tendency to avoid effort. While the "law of least effort" suggests humans prefer less costly behaviors, previous research identified an "effort paradox" where individuals sometimes select harder tasks, particularly when reward prospects increase. The authors hypothesized that this behavior might be driven by differences between objective performance costs (actual difficulty) and subjective effort costs (perceived aversiveness). The study aimed to determine whether voluntary switches to difficult tasks are predicted more by these objective metrics or by subjective valuations of effort. The researchers conducted two experiments with 100 participants each. In Experiment 1, participants performed a hybrid task-switching paradigm involving an easy letter-categorization task and a difficult prime-number identification task. Trials included forced choices and free choices, with reward cues indicating high or low potential earnings. Following the switching phase, participants completed an Effort Discounting Task (EDT) to measure subjective effort costs. In the EDT, participants chose between performing a difficult task block for a fixed monetary reward or an easy task block for a variable, lower reward. The indifference point in this staircase procedure quantified the amount of money participants were willing to forego to avoid the difficult task, serving as a proxy for subjective effort cost. Objective effort costs were calculated as the reaction time difference between the difficult and easy tasks. Experiment 2 replicated this design using a different set of tasks to ensure generalizability. The results demonstrated that voluntary switches to the difficult task were significantly predicted by objective performance costs but only marginally by subjective effort costs. In Experiment 1, multiple regression analyses showed that individual reaction time differences (objective costs) were a strong, significant predictor of the voluntary switch rate, whereas subjective effort costs derived from the EDT were not significant. Participants who experienced lower objective costs (smaller RT differences) were more likely to switch to the difficult task. This pattern held true both for overall switch rates and specifically for switches occurring when reward prospects increased. Experiment 2 confirmed these findings, showing that objective costs remained the primary predictor of task choice, while subjective costs had negligible predictive power. Additionally, the study replicated previous findings that reward increases significantly boost switch rates, particularly for difficult tasks. The findings suggest that the deliberate choice of difficult tasks is less irrational than previously assumed and is largely driven by economic considerations regarding actual performance efficiency. Rather than being motivated by a subjective enjoyment of effort or a disregard for cost, participants appear to base their choices on the objective ease of execution. This distinction clarifies the effort paradox by showing that when objective costs are low, the perceived barrier to switching diminishes, allowing reward incentives to drive task selection. The study implies that models of action selection should prioritize objective performance metrics over subjective effort valuations when predicting voluntary behavior in task-switching contexts.

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• task switching