colored plastic tokens, which the chimpanzees could manipulate and stick to a magnetic board. Each token stood for a word which was never spoken in the chimpanzee's presence. Sarah began her language training in 1967 at age 5, beginning with food exchanges, to establish a social exchange with the instructor. The Premacks note that the chimpanzees gave food reluctantly and unwillingly, far preferring to receive food. In a series of experiments, Premack was able to train Sarah, Elizabeth, and Peony to parse sentences: Peony nose touch which might result in Peony touching the trainer's nose. The tokens did not resemble the objects; an apple was symbolized by a blue triangle token. The chimpanzee Elizabeth would be symbolized by a decorated E token, a copy of which would dangle from a necklace around her neck. The trainer would also wear a corresponding token, as would other investigators whom the chimpanzee would have to name in the formation of the target sentence. It took Sarah, Elizabeth, and Peony each hundreds of trials to first form an association between the tokens and the objects. Sarah in particular was trained in the token manipulations for 18 months. Sarah was able to learn imperative sentences with a grammar, Sarah jam bread take in which the trainer allowed her to take the bread and jam, and also negative sentences No Sarah honey cracker take in which the trainer restrained her from taking the cracker and honey, which taught Sarah to suppress her impulse to take the negated object. In particular, the noun had to be at the beginning and the verb had to be at the end of the production, or else the trainer would not respond to Sarah's ungrammatical sentence. After hundreds of trials, Sarah could reliably produce the grammatical form Mary give apple Sarah List of tokens Nouns Sarah Mary (Mary Morgan, Sarah's favorite trainer) pail dish chocolate apple banana apricot raisin Verbs is give take insert wash Concepts/conditionals same different no-not name-of color-of "?" if-then Colors (tokens were not colored with the corresponding colors) red yellow brown green Questions Sarah was also able to answer questions in the form of a question token "?" which she could answer by selecting a resolving token. However, Sarah was never able to ask questions by manipulating the "?" token. The question "What is the color of apple?" "?" color of apple (blue triangle) would be answered