A Stanford University study published last month in the Proceedings of the National Academy of Sciences, "Cognitive control in media multitaskers", confirms what seems obvious to many: multitasking, often undertaken for efficiency's sake, is definitely counterproductive. This study looked at a well known, but often disregarded, phenomenon in IT: constant, ongoing multitasking. Agile implementors take note: there's good reason to urge each team to work on one product, with one product owner - splitting attention across many different tasks is a less effective way to work.
Wired Magazine notes that, whereas other studies have focused on multitasking’s immediate effects (for example office workers productivity while constantly checking email), this study asked a different question: “What happens to people who are multitasking all the time?” Stanford researchers Clifford Nass, Anthony Wagner and Eyal Ophir surveyed 262 students on their media consumption habits. The 19 students who multitasked the most and 22 who multitasked least then took two computer-based tests, each completed while concentrating only on the task at hand.
Using several standard psychological benchmark tests of focus, the study showed that college students who routinely juggle many flows of information, bouncing from e-mail to web text to video to chat to phone calls, fared significantly worse than their low-multitasking peers. Researchers were particularly surprised that what they called "heavy media multi-taskers" performed worse on a test of task-switching ability, "likely due to reduced ability to filter out interference from the irrelevant task set."
This study again confirms what cognitive scientists have said all along: processing multiple incoming streams of information is considered a challenge for human cognition.
As for what caused the differences — whether people with a predisposition to multitask happen to be mentally disorganized, or if multitasking feeds the condition — “that’s the million dollar question, and we don’t have a million dollar answer,” said Nass.
Wagner next plans to use brain imaging to study the neurology of multitasking, while Ness wants to look at the development of multitasking habits in children.