IT WILL doubtless come as something of a shock to discover that mobile telephones might be good for you. In the 20 years since they were introduced, cell-phones have been accused of causing (in roughly ascending order of significance) headaches, depression, memory loss and brain cancer. Learned papers have been written on how the microwaves they emit might produce subtle biochemical tweaks sufficient to cause at least some of these problems. And newspapers, ever eager for a good health scare, have happily devoted space to such stories. But the most recent research, by Alan Preece of Bristol University and his colleagues, could find no ill-effects from mobile-phone use. In fact, the researchers found the opposite: using such phones may speed up an individual's reactions.
Dr Preece's research, which has just been published in the International Journal of Radiation Biology, looked at the effect on 15 different aspects of brain function of microwave radiation similar to that from a mobile phone. His tests included such things as responding to particular words on a computer screen, responding only when two digits on the screen were the same, and remembering words, numbers and pictures that had been shown before. For the purposes of analysis, he grouped the results into four sets: reaction time, memory speed, memory accuracy, and accuracy of attention.
The “phone” in the experiment was actually a phone-shaped headset under computer control. It was clamped to a subject's left ear (most subjects were right-handed, and applying it to the right ear of the few left-handed participants would have added a needless variable). In two-thirds of the trials, a microwave signal at the operating strength and frequency of a mobile phone was broadcast from the headset into the subject's brain. In the other third, which acted as controls, no signal was broadcast—and neither subject nor experimenter knew which was which until after the trials were over.
The subjects had to endure this indignity for half an hour per trial, as they jumped through Dr Preece's hoops. The upshot was that all their recorded brain functions were normal (or, at least, did not differ between active and control runs), except for their so-called “choice” reaction times—how fast they could respond correctly to the appearance of a particular word on the computer screen. That was improved by an average of 4%.
This effect appeared in two independently tested groups of subjects, so, although it was small, it was probably not a fluke. Why reaction time should improve is a difficult question to answer. Dr Preece's best guess is that the slight heating effect of the microwaves may be responsible—perhaps by speeding up some critical chemical reaction or by stimulating blood flow. But that is, indeed, only a guess.
This work does not, of course, have much to do with the most serious accusations against mobile phones, which concern long-term exposure, not the odd half-hour gossip to a friend. But it should dispel the idea that the microwaves are having an immediate bad effect. It also suggests that hotheads may indeed react faster to provocations from the outside than the rest of us.
This article appeared in the Science & technology section of the print edition under the headline "Hotheads and cell-phones"