A Tip for Multi-Taskers: Less Is More

Scientists using sophisticated psychological tests and brain imaging technologies have reached this conclusion: It is hard to rub your stomach and pat your head at the same time.

So is taking an order while you’re deciding which restaurant table needs more coffee, or talking on the phone with a client as you check your stocks online.

It turns out that a chronic fact of 21st-century life--multi-tasking--actually, gasp, might be a waste of time. And people who are doing the juggling probably don’t even know it.

“A lot of time people have illusions about what is possible or impossible,” said David E. Meyer, a professor of mathematical psychology at the University of Michigan and coauthor of a study on multi-tasking published in the Journal of Experimental Psychology: Human Perception and Performance. “That may lead you to believe you have abilities or limitations that don’t really apply.”

His conclusion is that rapidly switching between tasks generally wastes time--sometimes a lot of it.

Meyer and his colleagues had young adults perform tasks of varying degrees of familiarity and complexity, such as alternately doing math problems and identifying geometric shapes. The researchers measured the time it took to complete the tasks.

“One of the surprises was the magnitude of time costs involved in task-switching,” Meyer said.

In some cases, multi-tasking added 50% to the time required to perform the chores.

The volunteers not only accomplished the tasks more slowly, they did them badly--even when the subjects were offered cash for jobs well done.

“Not only speed of performance, the accuracy of performance, but what I call the fluency of performance, the gracefulness of the performance, was negatively influenced by an overload of multi-tasking,” Meyer said.

Similarly, scientists at Carnegie Mellon University in Pittsburgh using brain-imaging technology found that the level of brain activity devoted to a task decreases when two tasks are performed at the same time, dragging down performance. They reported recently in the journal NeuroImage that people performing two activities at once do neither one as well as when they do one at a time.

Meyer said some people can perform some tasks simultaneously and do save time, particularly if the tasks are familiar.

But for most, time-saving is an illusion, he insisted.

The Michigan study, which was paid for by the Navy and conducted in part by the Federal Aviation Administration, could lead to better design of crucial jobs, such as air traffic control and vehicle operation, so that multi-tasking doesn’t hurt performance, Meyer said.

Dealing with multi-tasking is a problem all society faces, he said.

“Technical and economic and other forces are creating a spiraling amount of multi-tasking required in our population. There is an explosion of multi-tasking. There’s going to be more. It’s not going to get better.”

The idea that multi-tasking simplifies life “is negatively seductive,” he said.