In cross-fostering, parents of one genetic stock rear young of a second genetic stock to study the effect of rearing on genetic predisposition. Chimpanzees Washoe, Moja. Pili. Tatu, and Dar were cross-fostered in households modeled as closely as possible after human infant environments. Washoe arrived when she was 9 or 10 months old. Moja, Pili. Tatu, and Dar arrived within a few days of birth. When the cross-fosterlings were present. American Sign Language (ASL) was the only language used by human foster families. Cross-fosterlings learned ASL from human adults and each other conversationally, without drills or special treats. Semantic range was like human semantic range - DOG for any dog. FLOWER for any flower, including dogs and flowers on first sight. The clumps mostly initiated conversations on their own after about two years, casually as human children do. as if bom with a motive to communicate. ASL is a naturally occurring human language permitting comparison with human development. Development of vocabulary and phrases was comparable to development of human children. Development of functional categories of answers to Wh-questions was comparable, even advanced, as was meaningfully contingent replies to probing questions. Cross-fosterlings also used expansion, reiteration and incorporation to maintain conversation. Pragmatics of gaze direction and turn taking as well as gaze direction and pointing developed in human patterns. They also developed human pragmatic devices to indicate agent, object, and instrument. Development was slower than human development, but without signs of asymptote. Longer years of cross-fostering should induce further progress.
展开▼
