【悲報】「マルチタスクが得意」な人、実験するとほぼいなかった

Many people say, "I am good at multitasking." But scientists say the brain cannot really do two thinking tasks at the same time. It switches quickly between them.

Each switch takes a little time and can cause mistakes. In one driving study, only 5 out of 200 people could do two tasks well at once. So it is better to do one thing at a time.

People often feel they are good at multitasking, but research suggests that the brain cannot truly perform two demanding tasks at the same time. Instead, it switches rapidly between them. In a 2001 study, people became slower every time they switched between tasks, and the delay was greater when the rules were more complex.

Each switch may take only a moment, but hundreds of switches a day add up. In a 2010 driving simulator study, only 2.5% of 200 participants could drive and do a memory task at the same time without any drop in performance. Another study found that people who multitask often tend to overestimate their ability and actually perform worse on related tests.

Answering emails during a meeting may feel efficient, but cognitive psychology suggests the brain rarely handles two attention-demanding tasks simultaneously. Instead, it switches between them, paying a task-switching cost each time it unloads one set of rules and loads another. A 2001 study showed that responses slowed with every switch and that the cost grew with rule complexity and switches to unfamiliar tasks. Do heavy media multitaskers get better with practice?

A 2009 Stanford study suggested the opposite: they were worse at ignoring irrelevant information and even at switching tasks. That study was small, however, and a 2017 replication and meta-analysis concluded that any such difference is small and inconsistent; it is also unclear whether multitasking causes distractibility or distractible people prefer multitasking. "Supertaskers" do exist. In a 2010 driving simulator experiment, 5 of 200 participants, or 2.5%, showed no decline when combining driving with an auditory memory and math task.

Even so, a 2013 study found that frequent multitaskers tended to have weaker working memory and an inflated view of their own multitasking ability. Practical strategies, such as checking notifications in batches and grouping similar tasks, are likely to work better than trying to do everything at once.