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The Grammar of the Body: Revealing the Foundations of Compositionality in Human Language

Final Report Summary - GRAMBY (The Grammar of the Body: Revealing the Foundations of Compositionality in Human Language)

Natural sign languages of deaf people recruit all of the visible components of the body to convey the components of language. The two hands convey the words, while the head can connect parts of sentences to each other and the face carries the information that is conveyed by intonation in spoken languages. Shifts of the torso distinguish parts of a story and participants from one another, and the two hands can behave independently, fulfilling different linguistic roles. Despite disparate physical channels, the linguistic components (words, phrases, sentences, topics, etc.) and their grammatical organization of sign language are essentially the same as those of spoken language. Language in both modalities is compositional: meaningful components combine and recombine, to create unlimited complex expressions. The Grammar of the Body project aimed to understand the composition of language and its origins by using the human body as its guide. What are the essential components? How do they combine and recombine into complex compositional language? How did all language begin? Unlike spoken languages, sign languages can arise anew at any time, shedding light on how a language is born. By comparing the language of older people in a new language to that of younger people, we learn how a language develops compositional structure and complexity. We investigated the language of different generations of three young and diverse sign languages in Israel: Israeli Sign Language (ISL), Al-Sayyid Bedouin Sign Language (ABSL), and Kfar Qassem Sign Language (KQSL). The study yielded theoretically significant results. In the early stages of language, signers string together simple sentences, while in later stages, signers systematically create complex sentences by embedding one sentence in another, indicated by signals of the hands, eyes and head. In telling a story, signers of all ages use all parts of the body to relate discourse units to each other, but only younger signers develop a system. They separate major events by combining actions of several articulators (torso and head) while indicating finer relations, like parts of a sentence, with fewer, smaller signals (slight tilts of the head). Linguistic structure and its bodily expression are tightly intertwined and emerge in tandem. These results contrast sharply with theories claiming that bodily externalization of language is secondary and separate from its mental form. Instead, our empirical studies show that the body is of primary importance, and intrinsic to the mental organization of language and its emergence. We then ask how might complex, compositional language have evolved in our species? Our work implicates a far more ancient communication system: the expression of intense emotion. In a study of face and body displays of athletes who just won or lost a competition, our observers attributed emotional states to specific features of face and body, and their combinations. Expanded body and face convey dominance; asymmetrical body posture is associated with goal obstruction (frustration, anger); lip corners up with happiness; raised inner brows with submission. Participants also reported positive empathy with dominant displays, suggesting an evolutionary advantage for vicarious empathy with winners. Reaching much, much farther back in evolution, we studied hand gestures and facial expressions of chimpanzees. We found for the first time that simultaneous hand and face components can be dissociated from one another and recombined, with different effects on other chimps. We call this property componentiality, and identify it as an evolutionary stepping stone to the compositionality of human language. To explore the full range of compositionality in contemporary human language, we created a sign language theatre laboratory, in which deaf actors combined sign language with gesture and pantomime, revealing the consummate grammar of the body through art.