Scientists have discovered that the brain can't do two things at the same time

The results of the study were published in the Quarterly Journal of Experimental Psychology.

The study was conducted by experts from Martin Luther University Halle-Wittenberg, FernUniversität in Hagen and Medical School Hamburg.

In the experiment, participants had to perform two tasks at the same time. With one hand, they had to determine the size of a circle that appeared on the screen for a moment. At the same time, the participants called out loud the pitch of the sound - high, medium or low.

Details

The scientists measured the speed of reaction and the number of errors. The experiment was repeated for 12 days to see if the practice helped them to cope with two tasks at the same time.

Over time, participants did indeed perform the tasks faster and more accurately. However, the results showed that even after prolonged practice, the brain still doesn't process two tasks at the same time.

According to the researchers, people just start switching between activities faster, which makes it feel like they're doing several things at once.

Benefits

The results of the study help us understand why multitasking often leads to mistakes.

Even if a person feels like they are doing several things at once, the brain is actually switching between tasks quickly. This switching requires extra effort and reduces accuracy.

This is especially important in situations where high concentration is needed, such as:

• driving and talking on the phone
• when working with machinery
• in professions where you need to keep track of several processes at the same time.

Scientists note that even small changes in a task can noticeably increase the number of errors.

Background

It was previously thought that after enough practice, a person could almost eliminate efficiency losses in multi-tasking. A new study shows that multitasking still has a limit due to the peculiarities of the brain.

Source

Torsten Schubert et al, Evidence for a Latent Bottleneck After Extensive Dual-Task Practice of a Visual-Manual and an Auditory-Verbal Task, Quarterly Journal of Experimental Psychology (2025)