In some countries, such as Sri Lanka and Tanzania, each school for the deaf may have a separate language, known only to its students and sometimes denied by the school; on the other hand, countries may share sign languages, although sometimes under different names (Croatian and Serbian, Indian and Pakistani).
Scholars are doing field surveys to identify the world's sign languages.
[5] There are at least 25 sign languages in Africa, according to researcher Nobutaka Kamei.
[6][7][8] Some have distributions that are completely independent of those of African spoken languages.
At least 13 foreign sign languages, mainly from Europe and America, have been introduced to at least 27 African nations; some of the 23 sign languages documented by Kamei have originated with or been influenced by them.