A masculinizing effect on the auditory systems of human females having male co-twins.
Spontaneous otoacoustic emissions (SOAEs) are continuous, essentially tonal sounds that are produced by many normal-hearing cochleas. In humans, females generally exhibit more SOAEs than males, a sex difference that exists from birth. However, it is shown here that females having male co-twins [opposite-sex dizygotic (OSDZ) females] exhibit about half the average number of SOAEs per ear observed in same-sex female twins or female non-twins. Indeed, the average in OSDZ females is about the same as that seen in males--twins or non-twins. The explanation offered here is that prenatal exposure to high levels of androgens has produced a masculinizing effect on the auditory systems of these OSDZ females. Prenatal masculinizing effects have long been recognized in certain litter-bearing mammals, but their existence in humans is not well-studied.
McFadden
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Department of Psychology, University of Texas, Austin 78712.
D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D000818:Animals; D001307:Auditory Perception; D003051:Cochlea / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006309:Hearing / Q000502:physiology*; D006801:Humans; D008297:Male; D008322:Mammals; D008571:Men; D012727:Sex Characteristics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014930:Women