Inter-Individual Differences in Executive Functions Predict Multitasking Performance – Implications for the Central Attentional Bottleneck

Szameitat, André J.; Students, Brunel; Ball, Caitlin; Boyce, Jessica; Buckley, Mark; Saylik, Rahmi; Ghani, Nargis; Omar, Ayan; Simon, Luwam; Senkoy, Asli; Kumar, Kirti; Smith, Barry; Tyler, Kai · 2022 · DOAJ

DOI: 10.3389/fpsyg.2022.778966

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Summary

This study investigates whether executive functions (EF) contribute to the performance costs associated with human multitasking, specifically addressing the debate between the "active scheduling" and "passive queuing" accounts of the central attentional bottleneck. The passive queuing account posits that multitasking delays are caused solely by a refractory period where tasks wait for serial processing. In contrast, the active scheduling account argues that EFs are required to coordinate task order, inhibit interference, and switch processing, thereby contributing significantly to multitasking costs. The authors hypothesized that if EFs are involved, individuals with known EF impairments or enhancements should exhibit corresponding deficits or improvements in multitasking performance. To test this, the researchers conducted a series of experiments using the Psychological Refractory Period (PRP) paradigm, which measures response times and error rates in dual-task conditions compared to single-task baselines. They compared six experimental groups against matched controls. Three groups were selected for presumed EF impairments: individuals with dyslexia, highly neurotic individuals, and nicotine-deprived smokers. Three other groups were selected for presumed EF improvements: frequent video gamers, bilinguals, and coffee consumers. Participants performed visual and auditory speeded choice-response tasks either singly or concurrently. The study analyzed multitasking costs, defined as the relative slowing in dual-task performance compared to single-task performance, to determine if EF capabilities modulated these costs. The results provided strong support for the active scheduling account. All six experimental groups showed significant interactions between group status and task condition. The groups with EF impairments (dyslexics, highly neurotics, and nicotine-deprived smokers) exhibited multitasking costs that were 23–36% higher than their respective control groups. Conversely, the groups with EF improvements (video gamers, bilinguals, and coffee consumers) demonstrated multitasking costs that were 20–25% lower than controls. These findings indicate that individual differences in executive function capabilities directly predict multitasking performance. The data suggest that the bottleneck is not merely a passive waiting period but involves active cognitive control processes that vary in efficiency across individuals. The significance of these findings lies in resolving a long-standing theoretical controversy in cognitive psychology. By demonstrating that multitasking costs are modulated by EF status, the study confirms that executive resources are actively engaged in coordinating concurrent tasks. This has practical implications, suggesting that populations with reduced EF capabilities may be more prone to errors, mental fatigue, and stress in multitasking environments. The results underscore the importance of considering individual cognitive differences when evaluating human performance in complex, dual-task scenarios.

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Topics

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• dual task multitasking
• cognitive capacity variation