The first systematic evaluation of the hearing of girls and boys was performed by Professor John Corso of Penn State University in the late 1950's and early 1960's.  Dr. Corso simply used a soundproof booth, headphones, and a tone generator.  He consistently found that the girls hear better than boys do, especially in the range of frequencies above 2 kHz. See John Corso, Age and sex differences in thresholds, Journal of the Acoustical Society of America, 31:498-507, 1959; also John Corso, Aging and auditory thresholds in men and women, Archives of Environmental Health, 6:350-356, 1963.

Likewise, Professor Jane Cassidy at Louisiana State University Professor Cassidy, in a study of 350 newborn baby girls and boys, found that the girls’ hearing was substantially more sensitive than the boys, especially in the 1000- to 4000-Hz range which is so important for speech discrimination. See Jane Cassidy and Karen Ditty. Gender differences among newborns on a transient otoacoustic emissions test for hearing. Journal of Music Therapy, 37:28-35, 2001.

A variety of more recent studies using more sophisticated technology have not only confirmed the superior hearing of girls at higher frequencies, but have also begun to demonstrate the anatomical basis for that superiority.  The group led by Hiroaki Sato was the first to demonstrate consistent sex differences in the anatomy of the inner ear:  girls are born with a cochlea which is shorter and stiffer than boys’.  The shorter, stiffer cochlea provides a more sensitive frequency response.  See their paper, Sexual dimorphism and development of the human cochlea.  Acta Otolaryngologica, 111:1037-1040, 1991.

A few years later, a French group led by Thierry Morlet demonstrated that the hair cells themselves are stiffer (and therefore more sensitive) in girls compared to the hair cells in boys.  See their paper, Development of cochlear active mechanisms in humans differs between gender, Neuroscience Letters, 220:49-52, 1996.

These differences may help to explain sex differences in language acquisition. For example, the average 18-month-old girl has a vocabulary of about 90 words, compared to just 40 words for the average 18-month-old boy; see figure (source: Simon Baron-Cohen, Svetlana Lutchmaya, and Rebecca Knickmeyer, Prenatal Testosterone in Mind: amniotic fluid studies, Cambridge, MA: MIT Press, 2004.

At the level of the cerebral cortex, there appears to be another mechanism in play which gives females greater hearing sensitivity, at least for spoken language.  When listening to natural language, right-handed females use both brain hemispheres.  Right-handed males use primarily the left hemisphere.  See for example Michael Phillips, Joseph Lurito and associates, Temporal lobe activation demonstrates sex-based differences during passive listening, Radiology, 220:202-207, 2001.  This paper contains some stunning and dramatic color images which illustrate gender differences in hearing.  A useful survey of many such imaging studies is provided by Kenji Kansaku and Shigeru Kitazawa in their article, Imaging studies on sex differences in the lateralization of language, Neuroscience Research 41:333-337, 2001.

Professor Corso was the first to demonstrate systematically that the female superiority in hearing at frequencies above 2 kHz gets larger as kids progress through adolescence and into adulthood and indeed throughout adult life.  More recent work has confirmed his findings.  See for example the following papers:

· J. D. Pearson and associates, Gender differences in a longitudinal study of age-associated hearing loss, Journal of the Acoustical Society of America, 97:1-10, 1995.

· Yasua Uchida and associates, Prevalence of self-perceived auditory problems and their relation to audiometric thresholds in a middle-aged to elderly population.  Acta Otolaryngologica, 123:618-626, 2003.  These researchers found that although men were far more likely to have hearing deficits than women were, men underestimated their hearing difficulties compared to the women.  Men don’t hear as well as women do, but most men are blissfully unaware of that fact.  A similar finding was reported by:

· B. Karlsmose and associates.  Prevalence of hearing impairment and subjective hearing problems in a rural Danish population aged 31-50 years. British Journal of Audiology, 33:395-402, 1999.  These researchers, studying almost a thousand adults in rural Denmark, obtained results very similar to those obtained in Japan by Yasue Uchida and associates.  Significant hearing deficits were far more common among men than among women, but hearing-impaired men were less likely to be aware of their deficit than hearing-impaired women were.

· Martti Sorri and P. Rantakallio.  Prevalence of hearing loss at the age of 15 in a birth cohort of 12,000 children from northern Finland. Scandinavian Audiology, 14:203-207, 1985.  This study demonstrated that hearing impairment is about 70% more common in teenage boys than in teenage girls.