The term 'deaf' should be applied only to individuals whose hearing impairment is so severe that they are unable to benefit from any amplification. Permanent or temporary deafness may be the result of: exposure to sound (stimulation deafness); injury; disease; or developmental anomalies, either early in life or during aging. About half of all hearing-impaired children suffer from hereditary deafness. Acquired deafness has been reduced with the help of antibiotics and vaccinations.
Many who are born deaf or who became deaf early in life experience language difficulties all through life; if no special education is available the child remains mute. Communication problems apart, there are indications that deafness has a pervasive effect on the total personality of the deaf person, including his social adjustment, perception and general motor activity. He is severely limited in understanding the world around him, in making himself understood, and in making the most of his learning experiences. He is deprived of the ability to enjoy not only music but also environmental sounds.
Myths and superstitious beliefs about causes of deafness reinforce negative attitudes and determine the way the deaf person is perceived and treated, even in his own family circle. In parts of east Africa, a congenitally deaf child is believed to be obeying an injunction by a god who has warned him not to divulge some secrets confided to him; to avoid possible risks, the child 'chooses' to be born deaf and mute. This, in turn, provides a reason for other people to avoid him.
Whereas the prevalence is practically the same in America, Asia, and Europe, there seem to be far fewer cases of deaf-mutism in Africa and Oceania although as yet there exists no indication of an ethnically determined predisposition to deaf-mutism. There are more cases of deaf-mutism among males than among females, even in countries where women outnumber men.