German children's comprehension of word order and case marking in causative sentences.

Two comprehension experiments were conducted to investigate whether German children are able to use the grammatical cues of word order and word endings (case markers) to identify agents and patients in a causative sentence and whether they weigh these two cues differently across development. Two-year-olds correctly understood only sentences with both cues supporting each other--the prototypical form. Five-year-olds were able to use word order by itself but not case markers. Only 7-year-olds behaved like adults by relying on case markers over word order when the two cues conflicted. These findings suggest that prototypical instances of linguistic constructions with redundant grammatical marking play a special role in early acquisition, and only later do children isolate and weigh individual grammatical cues appropriately.