Connecting a battery across the front of the head can boost verbal skills, says a team from the US National Institutes of Health.

A current of two thousandths of an ampere (a fraction of that needed to power a digital watch) applied for 20 minutes is enough to produce a significant improvement, according to data presented this week at the annual meeting of the Society for Neuroscience, held in San Diego. And apart from an itchy sensation around the scalp electrode, subjects in the trials reported no side-effects.

Meenakshi Iyer of the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, ran the current through 103 initially nervous volunteers. “I had to explain it in detail to the first one or two subjects,” she says. But once she had convinced them that the current was harmless, Iyer says, recruitment was not a problem.

The volunteers were asked to name as many words as possible beginning with a particular letter. Given around 90 seconds, most people get around 20 words. But when Iyer administered the current, her volunteers were able to name around 20% more words than controls, who had the electrodes attached but no current delivered. A smaller current of one thousandth of an amp had no effect.

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