Why are females echoes stronger?
Females tend to have much better hearing sensitivity than males. Their inner ears also tend to make stronger sounds, although the sounds have no real purpose in themselves. I was interested in the origins of this. Something we did years back was to measure the otoacoustic emissions in opposite-sex twins. And what we found was that those females had otoacoustic emissions that were like those of males, not other females. Since we knew from other research that otoacoustic emissions are reasonably stable through life — infants and children have them in the same pattern and manner that adults do — the implication was that those females with male twins had in fact been born with weaker cochlear amplifiers, that is, with weaker click-evoked emissions. So that leads you to try and imagine what kinds of mechanisms might have been operating prenatally to produce this effect. What we came up with was the suggestion that those females who had male twins were exposed to higher levels of androgens
