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Self-control may not diminish throughout the day

Regardless of time of day, performance on a specific task may decrease over time

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Credit: Randles et al (2017)

Our self-control may not be a finite resource that diminishes throughout the day, but we may still experience fatigue while persisting in a single task, according to a study published September 20, 2017 in the open-access journal PLOS ONE by Daniel Randles from the the University of Toronto, Canada and colleagues.

Previous studies have suggested that we have a finite resource of self-control, and thus have theorized that our motivation for cognitively challenging activities will deplete throughout the day. However, recent attempts to demonstrate people losing motivation on tasks throughout an entire day have failed to yield sufficient evidence to support this theory.

To investigate whether we have a finite amount of self-control, Randles and colleagues monitored two groups of students (N1 = 8,867, N2 = 8,754) over separate 17-week intervals with 24-hour coverage, as they engaged in voluntary learning and self-testing using an online program. The researchers assessed what time the students logged into the program, how long they persisted at a session, and how successful they were at the memory tests, and constructed a model from this data.

The researchers found that time of day had very little effect on students' success at completing the tasks, which is contrary to the theory that our self-control depletes throughout the day. The researchers found that a student could concentrate on a single task for about an hour before their performance depleted on that specific task, which is consistent with previous research, but the time of day at which the task was performed did not affect performance.

In order to access this information, this study did not consider demographics or what the students thought about the task, which the authors suggest would be important details to allow for a more complete interpretation of the results. However, they maintain that this research casts some serious doubt on the theory that we have a limited reservoir of self-control to draw from throughout the day, and hopefully opens the door for additional studies on motivation.

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In your coverage please use this URL to provide access to the freely available article in PLOS ONE: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0182980

Citation: Randles D, Harlow I, Inzlicht M (2017) A pre-registered naturalistic observation of within domain mental fatigue and domain-general depletion of self-control. PLoS ONE 12(9): e0182980. https://doi.org/10.1371/journal.pone.0182980

Funding: The 1st author (Daniel Randles) received financial support provided by the Social Sciences and Humanities Research Council of Canada, Banting Postdoctoral Fellowship (RN242784-BFP-SSHRC-01045). The 2nd author (Iain Harlow) received financial support provided by Cerego, a private corporation. Cerego provided support in the form of salary and supplied data (gathered during their normal business operation). The 3rd author acknowledges support from the Social Sciences and Humanities Research Council and Natural Sciences and Engineering Research Council of Canada. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript, beyond what was previously described. The specific roles of all authors are articulated in the "author contributions" section.

Competing Interests: The 2nd author, Iain Harlow, is an employee of Cerego. Additionally, Cerego provided the dataset for our analysis. Their ownership of the data prevents us from freely publishing and distributing the data. However, we have permission to distribute the data to requesting individuals, provided they list who will have access to the data, not re-distribute the data, and only publish summary statistics from subsequent analyses. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

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