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In a revealing set of studies, a team led by Gloria Mark and Victor Gonzalez of the University of California at Irvine tracked 36 officeworkers--in this case information-technology workers at an investment firm--and recorded how they spent their time, minute by minute. The researchers found that the employees devoted an average of just 11 minutes to a project before the ping of an e-mail, the ring of the phone or a knock on the cubicle pulled them in another direction. Once they were interrupted, it took, on average, a stunning 25 minutes to return to the original task--if they managed to do so at all that day. The workers in the study were juggling an average of 12 projects apiece--a situation one subject described as "constant, multitasking craziness." The five biggest causes of interruption in descending order, according to Mark: a colleague stopping by, the worker being called away from the desk (or leaving voluntarily), the arrival of new e-mail, the worker switching to another task on the computer and a phone call.
Of course, not all interruptions are created equal. Some are related to the job at hand and may be helpful--if not to the individual, then maybe to the team. Some are unrelated but nonetheless welcome: the Basex report found that 62% of workers at all levels said being interrupted by a friend with a nonbusiness-related question was "acceptable" (though the boss might take a different view). Several studies, including one by Mary Czerwinski, a senior researcher at Microsoft, show that interruptions at the beginning and the end of a task are the most detrimental to performance. An interruption when work has just got under way "blows away the goals you've established," says Czerwinski, while a ping or a knock at the end of the process "breaks the train of thought as people are reflecting and preparing for what they'll do next."
While the researchers did not look specifically at the quality of the work, a long history of psychological research has proved what one might expect: performance declines--and stress rises--with the number of tasks juggled. Similarly, there's a long-held principle in psychology that maintains that a little stimulation or arousal improves performance but too much causes it to decline. "If you apply that law to multitasking," says Mark, "you would expect that a certain amount of multitasking would increase arousal, perhaps leading to greater efficiency. But too much will produce declining performance."
Jonathan Spira, CEO and chief analyst at Basex, suspects that so-called NetGen'ers-- those who grew up IMing, Googling and texting--are less stressed by gadget-abetted multitasking than are older workers. "Younger people may actually be wired a little differently," he says. But, he adds, there's no getting away from the fact that to do your best work on difficult tasks, "sometimes you need to shut everything else out and focus."