The order of testing effect in otoacoustic emissions and its consequences for sex and ear differences in neonates

The amplitude values of transient-evoked otoacoustic emissions, recorded from a large sample of neonates, were used to examine the asymmetry between ears tested and the differences due to the sex of the subject. Whilst the sex difference, with females having larger responses than males, has been a consistent finding in previous reports, the right/left ear difference, with the right ear giving a larger response than the left, has produced variable results that differed between laboratories. In this study, the sex difference was confirmed with females giving a 1.2 dB greater response than males. It was not affected by the age of the neonate. A significant effect of test order was found. The measured right/left difference was enhanced when the right ear was tested first but was diminished when the left ear was tested first. If the left ear is tested first then the measured right/left difference would be about 0.5 dB whereas, if the right ear is tested first, the measured right/left difference would be about 1.5 dB. When male/female comparisons were made for right and left ears separately and for the same ear tested first, the sex differences were the same for all four conditions. The sex and right/left differences have been confirmed as statistically significant effects and the order effect could explain the discrepancies and variability of the right/left differences reported in the literature.