Sign language acquisition from different points of view

Sign language is naturally acquired by deaf and hearing children of deaf parents. This developmental process was investigated by researchers in many countries: the results of some studies demonstrate similarities and parallels in acquisition of spoken and sign languages, whereas other data indicate the specificity and differences in the path of sign language acquisition, compared to spoken language. In this paper, studies conducted over the past twenty years are overviewed and juxtaposed; this analysis of sign language acquisition research contains controversial subjects about stages of sign language acquisition. The themes explored in this paper are: manual babbling, appearance of first sign and vocabulary and grammar acquisition in deaf and hearing children of deaf parents, whose first mode of communication is sign language.