MONDAY, Aug. 24 (HealthDay News) -- You may think e-mailing, texting, talking on the phone and listening to music all at once is making you more efficient, but new research suggests the opposite is true.
Processing multiple streams of information from different sources of media is a challenge for the human brain, according to a study published in this week's online issue of the Proceedings of the National Academy of Sciences.
New research shows that students who did the most multi-tasking were less able to focus and concentrate -- even when they were trying to do only one task at a time.
"The human mind is not really built for processing multiple streams of information," said study author Eyal Ophir, a researcher at Stanford University's Communication Between Humans and Interactive Media Lab. "The ability to process a second stream of information is really limited."
Researchers had 262 college students fill out a questionnaire to determine how often they multi-tasked. Students were then asked to complete a series of tests that measured cognitive control, or the process by which the brain directs attention, decides where to allocate mental resources at a given moment and determines what's important from the many bits of information being received.
Students who were at the upper end of the media multi-tasking spectrum performed more poorly on all the tests than those who multi-tasked the least, even though the students had similar overall intelligence, including SAT scores.
In the first test, students were asked to determine how the orientation of red rectangles had changed while ignoring blue rectangles. The heavy multi-taskers had a harder time filtering out the useless information.
"The heavy multi-taskers couldn't help paying attention to the blue rectangles and were actually less successful in remembering the orientation of the red rectangles," Ophir said.
In another test, students were asked whether they were seeing an even or odd number or a vowel or a consonant when shown a letter and a number simultaneously. A prompt asked students to answer either the letter question or the number question.
Frequent multi-taskers took longer to answer than lighter multi-taskers, indicating they had a more difficult time switching between numbers-based and letters-based tasks.
"This was shocking," Ophir said. "You'd think multi-taskers would be better at task-switching, but they were slower."
The reasons for the decreased cognitive control are unclear, Ophir said. Researchers cannot say if the multi-tasking itself damages cognitive control -- and if so, how much multi-tasking it takes for damage to occur -- or if those who tend to multi-task with media have less cognitive control to begin with.
"Either way, the prescription is to multi-task less," Ophir said. "The big take-away from me is to try to build periods of focus, to create times you are really focused on one thing."
Media multi-tasking includes doing one or more activities at once, including e-mailing, surfing the Web, writing on a computer, watching TV, texting, playing video games, listening to music or talking on the phone.
"It seems from our survey that everybody is doing some amount of multi-tasking," Ophir said. "It's hard to find people that don't multi-task. But it's all about intensity."
The findings have implications for today's universities and workplaces, where multi-tasking has become the norm, said Dr. John Lucas, a clinical assistant professor of psychiatry at Weill-Cornell Medical College.
"There is no free lunch in switching from one task to another," Lucas said. "People multi-task without an awareness that transitioning from one set of responsibilities to another involves some lag time, and when they do switch, the cognitive skills are not going to be as sharp."
While computers are well-equipped to switch rapidly from one task to another, the human brain struggles with such demands. "The human brain is not a hard disc that can switch from one part of the drive to the other," Lucas said. "The average person is going to have difficulty performing two tasks as well as he or she would have performed one task and being focused on it over time."
The Kaiser Family Foundation has more on youth and media multi-tasking.
SOURCES: Eyal Ophir, M.S., researcher, Stanford University's Communication Between Humans and Interactive Media Lab, Palo Alto, Calif.; John J. Lucas, M.D., clinical assistant professor, psychiatry, Weill-Cornell Medical College, New York City; Aug. 24-28, 2009, Proceedings of the National Academy of Sciences