Emergence of New Communication Systems

Among human populations, language contact is the norm, and it often leads not only to language change (cf. "Innovation (language change and variation)") but also to the birth of new languages that arise in either spoken or signed form. In spoken language, two or more languages may come into direct contact via trade, colonization, importation of a foreign labor force, or some combination of these factors. Often in such situations, one of the populations coming into contact represents a sociopolitically and economically dominant culture known as the "superstrate," and the subordinate or subjugated culture or cultures are known as the "substrate". Typically in these situations, the substrate population vastly outnumbers the superstrate population. The substrate population may consist of different language groups, and the superstrate culture may deny or restrict directly or indirectly the access of the substrate population to educational opportunities. In an attempt to arrive at a common mode of communication, vocabulary is drawn mostly from the superstrate language with few to none of its structural properties. The result is referred to as a "pidgin", which has a lexicon adequate for everyday communicative purposes but little to no structural regularity. Over a few generations, a pidgin can begin to develop its own structural regularities on the way to becoming a fully linguistic system known as a "creole". Creole languages have been studied extensively because they tend to exhibit very similar structural properties, even though they arise in different parts of the globe from completely different superstrate and substrate languages. One hypothesis among many proposed has been that children born into pidgin-speaking populations add structural complexity and regularity to the language system they are exposed to, thus driving the development of a pidgin toward a full-fledged creole language.

There is no known parallel in animal communication of two or more systems merging to produce an emergent system that differs from either/any of the original systems. There is a documented case of one humpback vocalization "dialect" supplanting another when an Indian Ocean population came into contact on the eastern coast of Australia with a Pacific population. (1) There was however no evidence of merger or of hybridization, let alone a new system emerging that differed from both of these original systems.

The situations that give rise to new sign languages are more happenstance. Of particular note among several documented cases of new sign languages are situations in Nicaragua and among a Bedouin community in Israel. (2, 3)  In Central America, deafness is not hereditary, but typically caused by viral infections. Prior to the Sandinista revolution in Nicaragua, children who lost their hearing were seldom schooled, nor were they exposed to any form of sign language. Under the Sandinista program of universal education, including special education, many deaf individuals who had previously lived apart from one another were brought together for the first time in centralized educational settings. Instruction was given in lip-reading and speaking, but students communicated gesturally with each other on their own, using gestural systems they had developed at home, or from interacting with others. Over time, a full-blown sign language known as "Nicaraguan Sign Language" emerged whose properties have been studied.

On the basis of studies comparing cohorts of students in the deaf schools by decade, it appears to be the case that it is indeed the younger members of the community who provide systematicity and add structural complexity to the language (4,5). This is also consistent with recent experimental research showing that when presented with an inconsistent artificial language system in which a particular pattern reliably occurs only 60% of the time, adult learners appear to be roughly at chance in using this pattern while children tend to regularize the 60% pattern and use it from 70% to 100% of the time (6).

The situation of the Bedouin community in Israel is in many ways different from that in Nicaragua: the typical cause of deafness is not childhood disease but hereditary deafness. (3) This means that deafness can appear more than once, indeed several times within an extended family. The frequency of deafness across families has led to wide use of the sign language among hearing as well as deaf members of the community. The signing community has existed over three generations, with conventionalization of lexicon and sentence structure. Younger signers in the Bedouin community produce longer utterances and sign at a faster rate than older generations of signers, which is one of several markers of language emergence and change over time.

There appears to be some evidence for species-specific complexity emerging across generations of zebra finches raised in isolation. It is well-known that when raised in isolation, male songbirds produce only a divergent, often reduced version of the full-fledged adult male species-specific song. It has been shown that when the only input to a young zebra finch raised in isolation is the divergent song of such an adult male raised in isolation, the younger zebra finch adds complexity to its own ouput. If this output is provided as the sole input to another zebra finch raised in isolation, it will likewise add complexity to its output. Over successive generations, the song of isolates eventually reverts to an approximation of the species-specific and genetically programmed song sung in the wild (7).