Over 40 percent of 6,000 drivers surveyed believe hands-free headsets are safe to use while driving, according to the Insurance Institute for Highway Safety. However, the National Transportation and Safety Board would most definitely disagree. The argument against hands-free devices boils down to this: it is not what you're doing with your hands, but rather, with your mind.

In light of numerous studies over several years, the NTSB recommended this week that states ban all forms of cellphone usage while driving, including hands-free devices. While the agency's controversial recommendation cannot force states or local governments to impose such measures, it does raise questions about the benefits of hands-free devices and almost certainly weighs heavily on legislators to act.

The senior vice president of research at the IIHS, Anne McCartt, told reporters, "There is a large body of evidence showing that talking on a phone, whether hand-held or hands-free, impairs driving and increases your risk of having a crash".

Associated Press reports that after recently examining over 300 studies regarding cellphone safety for the Governors Highway Safety Association, Jim Hedlund couldn't recall a single study that showed hands-free equipment lowered the risk of automobile accidents versus simply using the cell phone in a traditional manner. Jim Hedlund is a safety consultant and a former National Highway Traffic Safety Administration official.

Similar results have also shown up in other countries. One study performed by the government of Sweden found, "There is no evidence suggesting that hands-free mobile phone use is less risky than handheld use." 

Marcel Just, a director at Carnegie Mellon University's Center for Cognitive Brain Imaging, seems to also agree with those findings. His research project puts individuals to the test inside a driving simulator while scanning their brain activity with an MRI device. When the drivers are spoken to, the result is approximately a 37% decrease in brain activity for areas thought to be responsible for performing tasks like driving. 

"The human mind can multitask, but each task is performed with less brain power and lower proficiency," Just said. "When someone is speaking your native language, you can't will yourself to not hear and process it. It just goes in," and ultimately even if the driver attempts to ignore the words, Just claims scientists, "can see activation in the auditory cortex, in the language areas." of the brain.