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Knowledge generalization and the costs of multitasking

Nature Reviews Neuroscience volume 24, pages 98–112 (2023)Cite this article

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Abstract

Humans are able to rapidly perform novel tasks, but show pervasive performance costs when attempting to do two things at once. Traditionally, empirical and theoretical investigations into the sources of such multitasking interference have largely focused on multitasking in isolation to other cognitive functions, characterizing the conditions that give rise to performance decrements. Here we instead ask whether multitasking costs are linked to the system’s capacity for knowledge generalization, as is required to perform novel tasks. We show how interrogation of the neurophysiological circuitry underlying these two facets of cognition yields further insights for both. Specifically, we demonstrate how a system that rapidly generalizes knowledge may induce multitasking costs owing to sharing of task contingencies between contexts in neural representations encoded in frontoparietal and striatal brain regions. We discuss neurophysiological insights suggesting that prolonged learning segregates such representations by refining the brain’s model of task-relevant contingencies, thereby reducing information sharing between contexts and improving multitasking performance while reducing flexibility and generalization. These proposed neural mechanisms explain why the brain shows rapid task understanding, multitasking limitations and practice effects. In short, multitasking limits are the price we pay for behavioural flexibility.

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Fig. 1: Multitasking performance limits and practice specificity in the laboratory.
Fig. 2: Cortical nodes corresponding to knowledge generalization and multitasking.
Fig. 3: Overlapping frontal–parietal–stratial brain regions involved in knowledge generalization and multitasking.
Fig. 4: Proposed limits in the generalizability of practice effects.
Fig. 5: How practice improves multitasking performance.
Fig. 6: Practice separates neural representations, which supports improved multitasking performance but attenuates flexibility and generalizability.

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Acknowledgements

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement no. 796329 awarded to K.G.G. and ARC Discovery Projects grants DP180101885 and DP210101977 awarded to P.E.D. The authors thank D. Lloyd for his work on the graphical representations of the concepts in this Perspective. The authors also thank C. Nolan, H. Bowman, J. Mattingley, Y. Wards and A. Renton for providing helpful feedback and insightful commentary on previous drafts.

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  1. School of Psychology, Faculty of Health and Behavioural Sciences, Queensland Brain Institute, University of Queensland, Brisbane, QLD, Australia

    Kelly G. Garner & Paul E. Dux

  2. Centre for Human Brain Health, School of Psychology, College of Life and Environmental Science, University of Birmingham, Birmingham, UK

    Kelly G. Garner

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Garner, K.G., Dux, P.E. Knowledge generalization and the costs of multitasking. Nat Rev Neurosci 24, 98–112 (2023). https://doi.org/10.1038/s41583-022-00653-x

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