Haarala C, Ek M, Bjornberg L, Laine M, et al. (2004).

This group of authors reported in a previous study that electromagnetic fields (EMFs) emitted by a mobile phone facilitate short term memory functioning (Koivisto, 2002b). In the present study they attempted to replicate their earlier findings. However, there were some modifications: the short term memory test was slightly modified, the phone battery was quieter, the phone was attached to the head more comfortably, exposure conditions were separated by 24 hours, and additional tests of cognitive function were included. Improvements in the methodology were that the testing was performed in two laboratories and was of a double blind design.

The tests were performed simultaneously in two independent laboratories in Finland and Sweden. In each, 32 volunteers were tested (16 men and 16 women). A memory test was used in which the subjects had to respond to a stimulus on a computer screen that had been shown up to 3 sequences before. Each subject performed the test twice, once with EMF exposure and once with sham exposure, with 24 hours between tests. The order of exposure was counterbalanced. Neither the researcher nor the subject was aware of the exposure status at the time of the test. The EMF was provided by a 902 MHz field, with mean power of 0.25W, pulsed at a frequency of 217 Hz, and with a pulse width of 577 µs. The SAR 10g average was 0.990 W/kg. Both the averaged SAR and the peak SAR were higher in this study than in the previous study.

The EMF had no effect on reaction times or on the accuracy of the subjects' responses. Similar results were observed in both laboratories.

The authors observe that several studies have shown speeding up of reaction times in tests of cognitive function, but state that the vast majority of the results in these studies were negative and that the positive tests could have occurred by chance alone. They further state that the appropriate statistical correction for multiple testing was not done in most of these studies.

The authors conclude that two alternative conclusions can be made regarding the effects of EMF on human short-term memory:
"One possible explanation is that the EMF has no effect and that the reported findings are false positives due to chance. Alternatively, the magnitude of the EMF effect may be so small that it can be detected only sporadically. So far, all the reported positive findings have suggested that the EMF facilitates cognitive functioning. This would support the latter conclusion."

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