Why can't the human brain multitask

Question to the brain

P.rof. Dr. Torsten Schubert, Psychology, Humboldt University Berlin: First of all, you have to clarify what exactly is meant by multitasking. Many processes are constantly taking place in our brain at the same time, most of them unconsciously. In psychology, however, we understand multitasking to mean that a person carries out two or more tasks in a time-overlapping manner. The tasks must have independent goals. That distinguishes multitasking from complex actions: Driving a car could be broken down into several tasks, but all of them have one goal, namely to get there efficiently and without accidents.

In principle, processes that belong to different tasks can now run at the same time - but there are certain restrictions. It is relatively unproblematic with peripheral processes, for example when we perceive things through different senses: I can listen to a conversation partner on the phone and take in visual information independently. Output processes can also often run simultaneously: I can speak and do something with my hand. In such cases there are at most minor mutual influences.

On the other hand, there are types of processes that the brain can only carry out one time at a time. A decision needs a kind of central attention, and this is indivisible. So if I am asked on the phone which appointment suits me better and at the same time my secretary asks by email whether she should print out certain documents, the two decision-making processes can only run one after the other. To turn to one thing is to interrupt the other. This is shown by psychological experiments: If decision-making processes overlap, the processing time increases or the error rate increases.

If you look at the neural level, then this corresponds very well with the idea that different brain centers are behind different types of processes. As soon as two tasks require different areas of the brain, the likelihood increases that they will not interfere with each other. However, many tasks involve both absorbing information and reacting accordingly. The brain areas that are responsible for the input must be linked to those that control the output. It is assumed that such a “binding” is strongly associated with the prefrontal cortex, which is also responsible for higher mental functions.

Brain research findings of the last two or three years now indicate that only one such binding is possible. That would mean that two tasks that require binding interfere with each other. That would be a good explanation of why using a cell phone while driving is so dangerous. On the other hand, the more familiar I am with a task, the faster such a binding can take place. How well someone can respond to different requirements at the same time always depends on the specific situation and the effects of practice. In addition, there are individual differences - contrary to popular prejudice, however, there is no fundamental advantage women have over men.

Recorded by Ulrich Pontes