Language Evolution and Computation Bibliography

Can a child who is not exposed to a model for language nevertheless construct a communication system characterized by combinatorial structure? We know that deaf children whose hearing losses prevent them from acquiring spoken language, and whose hearing parents have not exposed them to sign language, use gestures, called homesigns, to communicate. In this study, we call upon a new formal analysis that characterizes the statistical profile of grammatical rules and, when applied to child language data, finds that young children's language is consistent with a productive grammar rather than rote memorization of specific word combinations in caregiver speech. We apply this formal analysis to homesign, and find that homesign can also be characterized as having productive grammar. Our findings thus provide evidence that a child can create a combinatorial linguistic system without external linguistic input, and offer unique insight into how the capacity of language evolved as part of human biology.

The movements we make with our hands both reflect our mental processes and help to shape them. Our actions and gestures can affect our mental representations of actions and objects. In this paper, we explore the relationship between action, gesture and thought in both humans and non-human primates and discuss its role in the evolution of language. Human gesture (specifically representational gesture) may provide a unique link between action and mental representation. It is kinaesthetically close to action and is, at the same time, symbolic. Non-human primates use gesture frequently to communicate, and do so flexibly. However, their gestures mainly resemble incomplete actions and lack the representational elements that characterize much of human gesture. Differences in the mirror neuron system provide a potential explanation for non-human primates' lack of representational gestures; the monkey mirror system does not respond to representational gestures, while the human system does. In humans, gesture grounds mental representation in action, but there is no evidence for this link in other primates. We argue that gesture played an important role in the transition to symbolic thought and language in human evolution, following a cognitive leap that allowed gesture to incorporate representational elements.

This article focuses on two roles of gesture and explores the changes that take place in the manual modality when it is employed to fulfill the functions of language on its own. Gestures reflect a global-synthetic image. Gesture is idiosyncratic and constructed at the moment of speaking and it does not belong to a conventional code. The gesture conveys nuances of the coastline that are difficult to capture in speech. Gesture allows speakers to convey thoughts that may not easily fit into the categorical system, which are offered by conventional language. The gestures that accompany speech are not composed of parts but instead have parts that derive from wholes that are represented by way of imagery. The imagistic base of gesture allows it to capture and reveal information that speakers may have difficulty expressing in speech. Gesture can also play a role in cognitive growth by providing an imagistic route through which ideas can be made active or brought into the learner's repertoire. The manual modality assumes an imagistic form when it is used in conjunction with a segmented and combinatorial system. Modern-day human communication systems are based on a segmented and combinatorial mode of representation that gives the system its generative capacity. The gestures that speakers produce in the manual modality can express information that they are often not able to express within the codified spoken system. This information is processed by the listener and becomes part of the conversation.

Segmentation and combination is a fundamental and ubiquitous feature of modern human languages. Here we explore its development in newly emergent language systems. Previous work has shown that manner and path are segmented and sequenced in the early stages of Nicaraguan Sign Language (NSL) but, interestingly, not in the gestures produced by Spanish speakers in the same community; gesturers conflate manner and path into a single unit. To explore the missing step between gesturers' conflated expressions and signers' sequenced expressions, we examined the gestures of homesigners: deaf children not exposed to a sign language who develop their own gesture systems to communicate with hearing family members. Seven Turkish child homesigners were asked to describe animated motion events. Homesigners resembled Spanish-speaking gesturers in that they often produced conflated manner+path gestures. However, the homesigners produced these conflated gestures along with a segmented manner or path gesture and, in this sense, also resembled NSL signers. A reanalysis of the original Nicaraguan data uncovered this same transitional form, primarily in the earliest form of NSL. These findings point to an intermediate stage that may bridge the transition from conflated forms that have no segmentation to sequenced forms that are fully segmented.

Deaf children whose access to usable conventional linguistic input, signed or spoken, is severely limited nevertheless use gesture to communicate. These gestures resemble natural language in that they are structured at the level both of sentence and of word. Although the inclination to use gesture may be traceable to the fact that the deaf children's hearing parents, like all speakers, gesture as they talk, the children themselves are responsible for introducing language-like structure into their gestures. We have explored the robustness of this phenomenon by observing deaf children of hearing parents in two cultures, an American and a Chinese culture, that differ in their child-rearing practices and in the way gesture is used in relation to speech. The spontaneous sign systems developed in these cultures shared a number of structural similarities: patterned production and deletion of semantic elements in the surface structure of a sentence; patterned ordering of those elements within the sentence; and concatenation of propositions within a sentence. These striking similarities offer critical empirical input towards resolving the ongoing debate about the 'innateness' of language in human infants.