Greenfield P M, Savage-Rumbaugh E S
J Comp Psychol. 1984 Jun;98(2):201-18.
Analysis of two chimpanzees' conversations with their teacher during a tool-use training task demonstrated that chimps use lexigrams, a humanly devised visual symbol system, selectively to encode perceived variability; that is, they generally used their symbols to differentiate alternative possibilities or to represent change or novelty in a situation. In contrast, they tended to leave unsaid what was unchanging, repetitive, or the unique possibility in a situation. Perceived variability influenced not only which symbols were selected but also utterance length: A single dimension of variability in a situation leads to single-lexigram utterances; multiple dimensions are associated with multi-lexigram utterances. This pattern of results indicates that the absence of formal grammatical structure in chimp language does not imply that utterances beyond one word in length are either rote strings or imitations. The chimps' tendency to mention the variable while leaving the constant or redundant unsaid is, moreover, strong support for the position that their use of a humanly devised symbol system is more than a series of conditioned responses.
对两只黑猩猩在工具使用训练任务中与它们的老师进行对话的分析表明，黑猩猩会选择性地使用词符（一种人为设计的视觉符号系统）来编码所感知到的变化；也就是说，它们通常用符号来区分不同的可能性，或表示一种情况中的变化或新奇之处。相比之下，对于情况中不变、重复或唯一的可能性，它们往往不予提及。所感知到的变化不仅影响选择哪些符号，还影响话语长度：情况中单一维度的变化会导致单字词符的话语；多个维度则与多字词符的话语相关。这种结果模式表明，黑猩猩语言中缺乏形式语法结构并不意味着超过一个词长度的话语要么是机械的字符串，要么是模仿。此外，黑猩猩倾向于提及可变的部分，而对不变或冗余的部分不予提及，这有力地支持了这样一种观点，即它们对人为设计的符号系统的使用不仅仅是一系列条件反应。
