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Scientific Frontline: "At a Glance" Summary: Cognitive Limits of Human Multitasking
- Main Discovery: The human brain is fundamentally incapable of true parallel processing or unlimited multitasking, even following highly extensive training, as cognitive processes depend on rapid sequential execution rather than simultaneous operation.
- Methodology: Researchers conducted three experiments requiring participants to simultaneously indicate the size of a visually presented circle using their right hand while verbally identifying the pitch of a concurrent sound as high, medium, or low. Performance speed and error frequencies were recorded across repeated trials spanning up to twelve days, specifically measuring the impact of minor task deviations on established cognitive routines.
- Key Data: While participants demonstrated improved speed and error-free execution over the initial twelve-day training period, introducing even the most minimal changes to the trained tasks immediately generated elevated error rates and prolonged task completion times.
- Significance: The results contradict the established psychological concept of virtually perfect time sharing, illustrating that cognitive optimization through sequencing has strict limits that render the brain highly susceptible to fatigue and errors during demanding simultaneous activities.
- Future Application: Understanding these cognitive bottlenecks provides critical data for improving work processes, learning environments, and safety protocols, particularly concerning everyday risks like distracted driving or high-stakes professions such as air traffic control and simultaneous translation.
- Branch of Science: Cognitive Psychology and Experimental Psychology.
- Additional Detail: The research was a collaborative effort by Martin Luther University Halle-Wittenberg, FernUniversität in Hagen, and Medical School Hamburg, with the findings formally published in the Quarterly Journal of Experimental Psychology.
Even with highly extensive training, the human brain is not really capable of performing two tasks simultaneously. Moreover, even the smallest deviations from trained routines can have a significant impact on how quickly and successfully people complete tasks simultaneously. This is shown by a new study conducted by Martin Luther University Halle-Wittenberg (MLU), the FernUniversität in Hagen and the Medical School Hamburg. It was recently published in the “Quarterly Journal of Experimental Psychology”.
In three experiments, the researchers investigated how people perform two tasks simultaneously that involve different senses: participants were asked to indicate the size of a circle that was briefly displayed with their right hand and simultaneously to say whether a sound played at the same time was high, medium or low. The speed at which the participants completed the tasks and the number of mistakes they made were measured. The tasks were repeated over a period of up to twelve days. The results showed that the more often the test subjects completed the test, the faster they solved both tasks without errors. Earlier studies with similar findings had therefore suggested that so-called dual-task costs, i.e. performance losses when working on two tasks simultaneously, could almost completely disappear after extensive practice. "This phenomenon, known as virtually perfect time sharing, has long been considered evidence of true parallel processing in the brain and proof that our brain is capable of unlimited multitasking. The results of our study clearly contradict this assumption," says psychologist Professor Torsten Schubert from MLU.
The new study shows that the underlying cognitive processes still do not run completely in parallel. What's more, even the smallest changes to the tasks caused the error rate to rise and the participants to take longer to complete the tasks. "Our brain is very adept at sequencing processes so that they no longer interfere with each other. However, this optimization has its limits. In particularly challenging situations, our cognitive apparatus therefore tires very quickly and becomes error prone," Schubert continues.
The study also provides new impetus for safety research. "Our results show why multitasking can often be risky in everyday life, despite routine, for example when driving and talking on the phone at the same time. This is also relevant for professions with complex activities where several tasks must be performed in parallel, such as air traffic controllers or simultaneous translators," says Professor Tilo Strobach from the Medical School Hamburg. Professor Roman Liepelt from the FernUniversität in Hagen adds: "Our study sheds new light on the limits of human information processing. Understanding such cognitive bottlenecks is crucial for improving work processes, learning environments, and safety measures in everyday life."
Published in journal: Quarterly Journal of Experimental Psychology
Authors: Torsten Schubert, Roman Liepelt, and Tilo Strobach
Source/Credit: Martin Luther University Halle-Wittenberg | Zum Seitenanfang
Reference Number: psy031126_01
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