Savage-Rumbaugh S, Rumbaugh D M, McDonald K
Neurosci Biobehav Rev. 1985 Winter;9(4):653-65. doi: 10.1016/0149-7634(85)90012-0.
A 4 year old pygmy chimpanzee (Pan paniscus) has spontaneously begun to use symbols for the purpose of communicating. Other apes have required training before they began to use symbols fluently. By contrast, this pygmy chimpanzee has begun to learn and appropriately employ graphic symbols simply as the result of exposure to human models. He has also spontaneously demonstrated an ability to comprehend many spoken English words and his multi-word utterances consistently provide more information than his single-word utterances.
一只4岁的倭黑猩猩（Pan paniscus）已经自发地开始使用符号进行交流。其他猿类在能够流利使用符号之前都需要接受训练。相比之下，这只倭黑猩猩仅仅由于接触人类示范就开始学习并适当地运用图形符号。它还自发地表现出理解许多英语口语单词的能力，而且它的多词表达始终比单字表达提供更多信息。
