Why multitasking could be bad for you

In June of this year, a Chinese motorist was caught driving while undergoing intravenous therapy and talking on the phone.  A needle providing the intravenous therapy was stuck in the back of his right hand, which had been holding his phone, while he used his left hand to hold the iron pole with the intravenous fluid bag and also the car’s steering wheel.  Police in the city of Wenzhou in southeastern Zhejiang province, China were on patrol on June 20 when they saw the motorist driving at 80km/h.

The driver told police he was rushing to carry out some urgent matters so had left a health clinic before his infusion was complete. He claimed that it was not dangerous for him to be driving at the time because he was good at multitasking. The police didn’t buy his multitasking defense and fined the driver 150 yuan and deducted four points from his driving license for dangerous driving and using a mobile phone while driving.

In a famous study of drivers chatting on mobile phones, David Strayer and Frank Drews found that diving while using a mobile phone is as dangerous as driving while drunk.

The problems of multitasking don’t end with driving.  Harvard Medical School knows first-hand that multitasking increases the number of mistakes people make— a resident doctor nearly killed a patient after a text message distracted her from updating a prescription.

These and other examples point to an undeniable truth: multitasking can be dangerous at its worst and inefficient at its best. Even simple can produce a kind of ‘attention interference’ when performed simultaneously.

Multitasking can refer to three different kinds of activity:

• Performing two or more tasks simultaneously,
• Switching back and forth among tasks, or
• Performing a number of tasks in rapid succession.

Ophir, Nassb, and Wagner of Stanford University found that multitasking is less productive than doing a single thing at a time. They also found that people who attempt to multitask regularly have trouble paying attention, recalling information, or switching from one job to another. In fact, they performed worse than those who regularly stick to one task at a time.

The researchers conducted three separate tests.  In each of their tests, they split the test participants into two groups: those who regularly do a lot of media multitasking and those who don’t.

In one experiment, the groups were shown sets of two red rectangles alone or surrounded by two, four or six blue rectangles. Each arrangement flashed twice, and the participants were asked to determine whether the two red rectangles in the second arrangement were in a different position than in the first. To do this, they had to ignore the blue rectangles.  Those who multitasked infrequently had no problem doing that, however, those that multitasked frequently found the blue rectangles distracting, resulting in poor performance on the task.

In light of this, the researchers next hypothesized that perhaps frequent multitaskers were better at memory-related tasks, like storing and organizing information.  So, in the second test, frequent multitaskers were shown sequences of alphabetical letters and were asked to remember when a letter was repeated. They did not perform well while the infrequent multitaskers did well.

Still wondering, the researchers designed a third test to see if frequent multitaskers might be better at switching from one thing to another faster and better than others. Test participants were simultaneously shown images of letters and numbers and were instructed what to focus on. When they were asked to focus on numbers, they had to determine if the digits were even or odd. When they were asked to focus on letters, they had to say whether they were vowels or consonants.  Once again, the frequent multitaskers underperformed those that multitasked infrequently.

Other researchers have come to similar conclusions after testing subjects’ ability to multitask. In a study conducted by Robert Rogers and Stephen Monsell, participants were asked to switch between two different tasks on every 2nd trial in 5 experiments and on every 4th trial in a final experiment. The tasks were to classify the numeric digits of a pair of characters as even/odd or the letter characters as a consonant/vowel.  Participants were slower when they had to switch tasks than when they repeated the same task. Moreover, increasing the time between each trial to allow test participants to mentally prepare for other task reduced but did not eliminate the cost of switching.  Rogers and Monsell concluded that there are two parts to the cost of task switching: one attributable to the time taken to adjust the mental control settings (which can be done in advance it there is time), and another attributable to competition of mental resources due to carry-over of the control settings from the previous trial (apparently immune to preparation).

Another study conducted in 2001 by Joshua Rubinstein, Jeffrey Evans and David Meyer found that participants lost significant amounts of time as they switched between multiple tasks and lost even more time as the tasks became increasingly complex.

Why is this?  Turns out, people are not actually doing both activities at the same time. People think they are concurrently working on different tasks because we can shift our focus very fast— sometimes in just a 10th of a second— but our brains are actually switching back and forth between the tasks, diverting mental energy from one part of the brain to another part of the brain in the process. Thus, the time to shift focus doesn’t matter as much as the bandwidth the brain requires to move back and forth, and overloading our bandwidth affects performance and the quality of the work that is produced.

Driving, as our friend in China must know, takes a great deal of mental bandwidth.  Individuals must take into account their speed, the road conditions, the behavior of other drivers, road signs, and many other things at the same time.  When scientists look at the MRI of an individual who is driving, a great deal of their brain is activated. Adding just one more layer, for example listing to music or talking on a phone, decreases the amount of attention or brain bandwidth going toward driving by about 37%.

Adding fuel to the anti-multitasking fire, a study from the University of Sussex in the UK indicates, it might actually be physically harming our brains. When the researchers compared the amount of time people spend on multiple devices to MRI scans of their brains, those who pursue a lot of multitasking activities exhibited less brain density in the anterior cingulate cortex, which is a region that encourages empathy as well as cognitive and emotional control. Moreover, this brain damage is not temporary!

It is still unknown if those whose engage in chronic media multitasking are born with an inability to concentrate or are damaging their cognitive abilities by taking in so much information at once.

However, one thing is clear: the minds of multitaskers are not working as well as they could. Multitasking is problematic because it results in information overload and reduces our cognitive abilities to think, process, and remember.  In addition, the more we multitask, the more we crave options, and the less able we are to choose.

So maybe it’s time to stop talking on the phone while driving or answering e-mails in the midst of reading a report at work.  By doing less, we could all might accomplish more.

This article is published in collaboration with The World Bank. Publication does not imply endorsement of views by the World Economic Forum.

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Author: Roxanne Bauer is a consultant to the World Bank’s External and Corporate Relations.

Image: A stockbroker looks at stock index numbers. REUTERS/Punit Paranjpe.