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In discussing human gesture, it is important to distinguish among three main types that serve different functions. First are conventionalized, culture-specific gestures known as "emblems" (such as the "thumbs up" or "OK" signs) that convey specific meanings. Emblems exhibit aspects of both arbitrary reference (cf. "Arbitrary reference") and standards of form (cf. "Well-formedness criteria") but not other properties of linguistic systems. The second main type of gesture is that accompanying human speech, which has been identified by gesture researchers as non-linguistic in nature. In contrast to language, its mappings are said to be non-arbitrary and context-sensitive, and to exhibit no standards of form. Co-speech gesture is also said to be non-linear, unsegmented, global, and synthetic, and it exhibits no duality of patterning: its form is generally determined by its meaning and/or its context. Co-speech gestures are categorized as indexical (e.g., pointing gestures), iconic or metaphoric, or as "beats" (i.e. gestures that reflect the rhythm of speech). Spontaneous gestures during speech do not combine to yield more complex gesture strings with novel meanings. Nonetheless, gesture and language seem to form a unified system: co-speech gesture typically occurs during speech, expresses the same meaning as speech, is synchronized with it, acquired with it, and breaks down with it in aphasic apopulations. The status and use of non-linguistic gesture in sign language is a topic of ongoing research, but researchers seem to agree that though signed languages have gestural origins, sign language does not replace gesture, and signers make use of both systems in discourse. The third main type of gesture is that which occurs as a means of communication in the absence of the vocal channel. This has been studied in both natural and laboratory settings: Deaf children who are not exposed to sign language in early childhood and who develop so-called "home sign" gestural systems for purposes of communicating with hearing family members, and hearing humans who are asked to gesture without speech while conveying information to others in experimental settings. In both settings, the idiosyncratic gestural systems that arise show properties of human language in incipient form, including word order that may differ from that of the gesturer's spoken language. The status of ape gesture in the wild is unclear, but apes have been observed to gesture in captivity in the context of food begging (also in the wild), sociosexual positioning, and regulation of conflict situations. Recent research has shown that dogs track and comprehend indexical pointing gestures. In light of these facts, it seems plausible that earlier hominids would have gestured as well.The universality of co-speech gesture in human linguistic behavior (even among the blind), the origins of signed languages in gesture, and the fact that language users of both speech and sign can switch fairly readily to using gesture as a sole means of communication all suggest that gesture may have played an important role in the evolution of language.
Body language: The interplay between positional behavior and gestural signaling in the genus Pan and its implications for language evolution., , Am J Phys Anthropol, 2015 Aug, Volume 157, Issue 4, p.592-602, (2015)
Hand and Mind, , Chicago and London, p.Chapters 1 and 2, pp. 11-72, (1992)