Thirty minutes exposure to a digital mobile phone can improve people’s working memory functioning, at least in the short term, according to Vanessa Keetley and colleagues at Swinburne University in Australia.
The performance of 120 participants on a battery of neuropsychological tests was compared before and after they were exposed for thirty minutes to a mobile phone that was either on full power, or switched off. The phone was clipped to a headset leaving it 0.5 to 1.5 cm from the participants’ heads. The researchers took pains to ensure neither the participants nor experimenters knew whether the phone was on or not. For example, the phone was covered in sound-proofing material to hide the slight buzzing sound it made when it was on, and a piece of foam prevented the participants from feeling whether the phone was warming up.
After exposure to radiofrequency electromagnetic radiation from the switched on phone, the participants were significantly quicker at a trail making task, a measure of working memory performance that required them to join up 25 circled digits, or a mixture of letters and digits, with a line. The researchers speculated the phone might have this effect by altering blood flow in the dorsolateral prefrontal cortex, an area involved in working memory.
However, exposure to a switched on phone slowed down participants’ performance on simple or choice reaction time tasks that required them to press a button as quickly as possible when they saw a particular on-screen stimulus.
“The negative effects of digital mobile phone exposure on reaction time performance indicate that the more basic functions were adversely affected by exposure. In contrast, the improved performance reaction time for the trail making working memory task suggests that digital mobile phone exposure has a positive effect on tasks requiring higher level cortical functioning, such as working memory”, the researchers concluded.
Keetley, V., Wood, A.W., Spong, J. & Stough, C. (2006). Neuropsychological sequelae of digital mobile phone exposure in humans. Neuropsychologia, 44, 1843-1848.