an interesting thing about first language aquisition is the degree of simularity in which children learn a langauge cross culturally and also in sign language. ths learning takes developmental sequances the first of which is crying to signal they want something. next we hear noises of interest made in babies on seeing intereting things. Although babies do not have good knowledge of the noises they are making the studies of peter eimas showed they could differentiate between sounds in human language.
by their first year most babies will understand phrases such as hello and goodbye and indications of food. by age two most babies know up to 50 words and can develop telegraphic sentences. in the 1960s roger brown discovered the grammatical morphemes. of children