Halle, Germany, Mar 13: A new study by researchers from Martin Luther University Halle-Wittenberg, FernUniversität in Hagen, and Medical School Hamburg has found that the human brain is not truly capable of performing two tasks simultaneously, even after extensive training. The findings were recently published in the Quarterly Journal of Experimental Psychology.
The research challenges the long-held assumption that people can achieve perfect multitasking through practice. Instead, the study shows that while training may improve performance speed and reduce errors, the brain still processes tasks sequentially rather than in true parallel.
The researchers conducted three experiments in which participants were asked to complete two tasks at the same time using different senses. Participants had to indicate the size of a briefly displayed circle using their right hand while simultaneously identifying whether a sound played was high, medium, or low. Scientists measured both the speed of responses and the number of mistakes made. The tests were repeated over a period of up to twelve days.
Results showed that participants improved over time, completing both tasks faster and with fewer errors as they practiced. Earlier research had suggested that such improvement could lead to “virtually perfect time sharing,” where multitasking performance losses disappear almost entirely.
However, the new findings contradict that idea. According to psychologist Torsten Schubert from Martin Luther University Halle-Wittenberg, the brain does not process the tasks fully in parallel. Even minor changes to the tasks significantly increased error rates and slowed participants’ responses.
“Our brain is very adept at sequencing processes so they no longer interfere with each other,” Schubert explained. “However, this optimisation has its limits. In particularly challenging situations, our cognitive system becomes tired quickly and more prone to errors.”
The study also has important implications for safety in everyday life and professional environments. Multitasking situations—such as driving while talking on the phone—can become risky despite familiarity or routine.
Tilo Strobach from Medical School Hamburg noted that the findings are particularly relevant for professions that require managing multiple tasks simultaneously, including air traffic controllers and simultaneous translators.
Meanwhile, Roman Liepelt from FernUniversität in Hagen emphasized that the research offers valuable insight into the limits of human information processing.
“Understanding these cognitive bottlenecks is crucial for improving work processes, learning environments, and safety measures in everyday life,” Liepelt said.
The study provides new evidence that while the brain can become highly efficient with practice, true multitasking remains beyond its limits.
