Multitasking Doesn't Work

Yesterday, I saw a YouTube video in which we are asked to complete two tasks in serial, and in parallel (multitasking). While I am not sure if the test is representative of multitasking in everyday life, it is obvious even from this simple exercise that multitasking is counterproductive.

Switching costs decrease efficiency, quality of experience, and accuracy, while raising stress levels. Multitasking on people degrades relationships.

[...] evidence suggests that the human "executive control" processes have two distinct, complementary stages. They call one stage "goal shifting" ("I want to do this now instead of that") and the other stage "rule activation" ("I'm turning off the rules for that and turning on the rules for this"). Both of these stages help people to, without awareness, switch between tasks.  

Although switch costs may be relatively small, sometimes just a few tenths of a second per switch, they can add up to large amounts when people switch repeatedly back and forth between tasks. Thus, multitasking may seem efficient on the surface but may actually take more time in the end and involve more error. Meyer has said that even brief mental blocks created by shifting between tasks can cost as much as 40 percent of someone's productive time.

It causes collateral damage beyond that inflicted on the multitasker. Maria Konnikova writes in the New Yorker,

When Strayer and his colleagues observed fifty-six thousand drivers approaching an intersection, they found that those on their cell phones were more than twice as likely to fail to heed the stop signs. In 2010, the National Safety Council estimated that twenty-eight per cent of all deaths and accidents on highways were the result of drivers on their phones.

The vast majority (~98%) of us cannot multitask well, and shouldn't delude ourselves.

I like the quote at the opening of Christine Rosen's essay,

In one of the many letters he wrote to his son in the 1740s, Lord Chesterfield offered the following advice: “There is time enough for everything in the course of the day, if you do but one thing at once, but there is not time enough in the year, if you will do two things at a time.” To Chesterfield, singular focus was not merely a practical way to structure one’s time; it was a mark of intelligence. “This steady and undissipated attention to one object, is a sure mark of a superior genius; as hurry, bustle, and agitation, are the never-failing symptoms of a weak and frivolous mind.”