Many Australian Aboriginal cultures have or traditionally had a manually coded language, a signed counterpart of their oral language. This appears to be connected with various speech taboos between certain kin or at particular times, such as during a mourning period for women or during initiation ceremonies for men, as was also the case with Caucasian Sign Language but not Plains Indian Sign Language, which did not involve speech taboo, or deaf sign languages, which are not encodings of oral language. There is some similarity between neighbouring groups and some contact pidgin similar to Plains Indian Sign Language in the American Great Plains.