T’is the season and all of that, so I’ll begin by noting that last year my husband gave my mother a hands-free cell phone kit. I thought the gift was motivated by a concern about her tendency to talk on the phone when she’s making the 90 minute trip to and from our house, but maybe the gift was more nefarious than I realized. Last week’s Economist is reporting on a study that shows even hands-free phones can dangerously impair driving skills:
Melina Kunar of the University of Warwick, in England, and Todd Horowitz of the Harvard Medical School ran a series of experiments in which two groups of volunteers had to pay attention and respond to a series of moving tasks on a computer screen that were reckoned equivalent in difficulty to driving. One group was left undistracted while the other had to engage in a conversation about their hobbies and interests using a speakerphone . . . . Those who were making the equivalent of a hands-free call had an average reaction time 212 milliseconds slower than those who were not. That, they calculate, would add 5.7 metres (18 feet) to the braking distance of a car travelling at 100kph (62mph). The researchers also found that the group using the hands-free kit made 83% more errors in their tasks than those who were not talking.
To try to understand more about why this was, they tried two further tests. In one, members of a group were asked simply to repeat words spoken by the caller. In the other, they had to think of a word that began with the last letter of the word they had just heard. Those only repeating words performed the same as those with no distraction, but those with the more complicated task showed even worse reaction times—an average of 480 milliseconds extra delay. This, the researchers suggest, shows that when people have to consider the information they hear carefully, as they might when making decisions about a business deal, it can impair their driving ability significantly.
Different studies have suggested that two other driving past-times—chatting with passengers and listening to the radio—do not have the same negative effects on driving. Researchers speculate that talking on the phone competes for the brain’s resources in ways that these other activities do not.