How is multi-tasking different from increased difficulty?

Abstract

With the advancement of technologies like in-car navigation and smartphones, concerns around how cognitive functioning is influenced by “workload” are increasingly prevalent. Research shows that spreading effort across multiple tasks can impair cognitive abilities through an overuse of resources, and that similar overload effects arise in difficult single-task paradigms. We developed a novel lab-based extension of the Detection Response Task, which measures workload, and paired it with a Multiple Object Tracking Task to manipulate cognitive load. Load was manipulated either by changing within-task difficulty or by the addition of an extra task. Using quantitative cognitive modelling we showed that these manipulations cause similar cognitive impairments through diminished processing rates, but that the introduction of a second task tends to invoke more cautious response strategies that do not occur when only difficulty changes. We conclude that more prudence should be exercised when directly comparing multi-tasking and difficulty-based workload impairments, particularly when relying on measures of central tendency.

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Data Availability

The data and materials for all experiments are available at https://osf.io/eb5ap/ and neither experiment was preregistered.

Notes

  1. 1.

    Note: We also applied the Racing Diffusion Model (Tillman & Logan, 2017), which was applied to similar data by previous authors (Tillman et al., 2017). The results of this model were qualitatively the same as the LBA, and the LBA was preferred by WAIC in all cases. Hence, for brevity, we only report the LBA analyses.

  2. 2.

    Note we frame posterior p-values as a test against the direction reported, so that a small p-value corresponds to high certainty. We report this way to be consistent with traditional frequentist p-values.

  3. 3.

    We plot standardized parameter distributions, so the magnitude of changes between drift and threshold is directly comparable.

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Author Note

This research was supported by an Australian Government Research Training Program (RTP) Scholarship awarded to Zachary Howard.

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Correspondence to Zachary L. Howard.

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Howard, Z.L., Evans, N.J., Innes, R.J. et al. How is multi-tasking different from increased difficulty?. Psychon Bull Rev 27, 937–951 (2020). https://doi.org/10.3758/s13423-020-01741-8

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Keywords

  • Cognitive workload
  • Bayesian modeling
  • Computational models
  • Multitasking