Detection thresholds for 60 Hz electric fields by nonhuman primates

Because responses of animals to detection of the presence of an electric field (EF) are a possible mechanism for production of biological effects, it is important to know what EF intensities are detectable. Operant methods were used to train six baboons (Papio cynocephalus) to perform a psychophysical task involving detection of EF presence. During the response phase of a trial, a subject responded on one push button to report the presence of the EF and on a different push button to report the absence of the EF. Correct reports of EF presence of absence produced delivery of food rewards. The subjects became proficient at performing this psychophysical detection task; during 35 days of testing, false alarm rates averaged 9%. The average EF detection threshold was 12 kV/m; the range of means among subjects was 5-15 kV/m. Two special test procedures confirmed that the subjects were responding directly to EF presence of absence and not to artifacts that might be associated with EF generation. The EF detection threshold of nonhuman primates is similar to thresholds reported for rats and humans.