Enculturated apes Kanzi , Washoe , Sarah and a few others who underwent extensive language training programs (with the use of gestures and other visual forms of communications) successfully learned to answer quite complex questions and requests (including question words "who" what", "where"), although so far they failed to learn how to ask questions themselves . For example, David and Anne Premack wrote: "Though she [Sarah] understood the question, she did not herself ask any questions — unlike the child who asks interminable questions, such as What that? Who making noise? When Daddy come home? Me go Granny's house? Where puppy? Sarah never delayed the departure of her trainer after her lessons by asking where the trainer was going, when she was returning, or anything else".  The ability to ask questions is often assessed in relation to comprehension of syntactic structures . It is widely accepted, that the first questions are asked by humans during their early infancy, at the pre-syntactic, one word stage of language development , with the use of question intonation .