It has long been understand that right-handed people -- who make up about 90 percent of the population -- have left-hemisphere dominant brains, and left-handed people the reverse. But the division of labor isn't actually that simple. For some 95 percent of righties, the left hemisphere almost exclusively handles language and the right emotion and image processing, while for lefties, only 20 percent experience such strict division.
Now there may be a new way, apart from handedness, to determine one's cerebral dominance: the cell phone.
In a new study out of Henry Ford Hospital in Detroit, published in JAMA Otolaryngology-Head & Neck Surgery, researchers found that most people who hold their cell phones to their left ear are right-hemisphere dominant, while most who hold their cell phones to their right ear are left-hemisphere dominant.
Now, one might ask, who cares? Lead researcher Michael Seidman, director of the division of otologic and neurotologic surgery in the Department of Otolaryngology-Head and Neck Surgery at Henry Ford, said in a school news release that these findings actually have several implications.
Not only could this help us better understand the language center of the brain, he said, but "by establishing a correlation between cerebral dominance and sidedness of cell phone use, it may be possible to develop a less-invasive, lower-cost option to establish the side of the brain where speech and language occurs rather than the Wada test, a procedure that injects an anesthetic into the carotid artery to put part of the brain to sleep in order to map activity."
What's more, the findings suggest that cell phone use may not be linked to brain, head, and neck tumors, given that nearly 80 percent of people studied hold the cell phone to their right ear and yet cancer doesn't appear more often on that side of the brain, head, or neck.
Dr. Seidman first looked into cell phone handedness when he noticed that most people use their right hand to hold their cell phone to their right ear, even though this would make listening on the phone while taking notes or other multitasking harder.
So the team out of Henry Ford sent online surveys to 5,000 people who were either patients undergoing Wada and MRI for noninvasive localization or with an online otology group. Most respondents (90 percent) were right-handed, with 9 percent left and 1 percent ambidextrous.
The survey included questions about time spent talking on cell phones, diagnoses of head or neck tumors, and hand dominance for tasks such as writing. Almost 70 percent of the righties held the phone to their right ear, 25 percent to the left, and 7 percent to either ear. In turn, 72 percent of the lefties used their left ears, while 23 percent used their right and 5 percent had no preference. (People with hearing differences between ears also preferred to use the dominant ear when talking on their phones.)
Meanwhile, the researchers note that studies are already under way investigating tumor registry banks of people with head, neck, and brain cancer to investigate possible links to cell phone use. Until we know more, Seidman suggests that people use their phones in hands-free mode when possible.