How Is Sign Language Acquired by Children?

 

Current linguistic theory which hypothesizes that humans are genetically endowed with the fundamental underpinnings of language is supported by the claim that languages are similar to each other in significant ways. This view gains further support from the sign language findings reported in the previous sections. As we mentioned earlier, current theories are also based on the related observation that children acquire language automatically, including aspects of the system that do not seem directly retrievable from the input they receive. This section reviews phases of The acquisition of sign language, to see whether this process has the hallmarks of automaticity and systematicity that are found in spoken language acquisition. If sign languages represent the same cognitive system as spoken languages do, then they should be acquired in a similar way. If, on the other hand, the modality somehow prevents sign languages from belonging to the same cognitive system, then they may be acquired quite differently. Furthermore, if the acquisition of language represents the unfolding of a biological-cognitive program with innate components, then sign languages should be acquired at the same rate as spoken languages. Whether or not the underlying cognitive system is the same, the possibility exists that the modality – oral / aural or manual / visual – has an impact on the course of development. These issues form the context for Sign language acquisition studies. Numerous studies have examined the acquisition of sign languages by deaf children whose parents are deaf signers. Although this population represents only 5 to 10 percent of deaf children, it is the relevant one to study because these children receive input in sign language from birth, just as hearing children receive input in their native language. In general, it has been found that deaf children who are exposed to sign language acquire it in very similar ways to the acquisition of spoken languages: they pass through the same milestones at the same rate. As one example, let us consider the child’s first words or signs. Research on the acquisition of spoken languages finds that on the average, children begin to use their first words at around 11 months of age. The age varies from child to child, but many studies across a variety of languages have converged on the same average age, so the acquisition of first words is often taken to be a milestone in language acquisition. When do the first words of sign language appear? Some early studies claimed that deaf children begin to use their first signs around 6 to 8 months of age, much younger than the reported first words. Why would there be such a difference between first words and first signs? Two types of mutually compatible explanation have been proposed. One suggests that meaningful gestures are sometimes mistaken for signs, implying that there may not be a significant difference for all children, and the other assumes the difference is real, but offers a physiological explanation for the difference. The first explanation points out that both deaf and hearing children make meaningful gestures during the time under consideration. If more stringent requirements are adopted for attributing “word / sign” status to some production of the child, the difference between the first spoken words and the first signed words shrinks to about one and a half months, or even disappears completely. Another possibility is that these first signs may be more easily recognizable by adult observers than first spoken words, due perhaps to iconic elements that stand out in communication contexts, or to the nature of visual perception. If this is correct, it would also point toward a smaller gap in the actual onset of first word production in the two modalities. The second explanation considers the development of the articulatory mechanisms used for speech versus sign. Earlier maturation of the mechanisms for muscular coordination of the hands and arms over the vocal organs may make it easier for a child who is cognitively ready for first words / signs to produce a sign than a spoken word. Such explanations put the possible difference between the onset of signs and words in “peripheral” mechanisms rather than the biological timetable for language. In other words, it may not be the case that signing is more advanced than speech, but, rather, that speech is delayed vis-à-vis sign. That is, children are cognitively ready to produce words before the coordination of the speech production system allows them to do so. This possibility is supported by evidence that (hearing) children comprehend words before they are able to produce them. The apparent discrepancy between the onset of first words in spoken versus signed language thus focusses important research questions that never would have even arisen if we considered only spoken language. These explanations downplaying the apparent difference between sign and spoken language development are all the more reasonable when other areas of language acquisition are considered, where there does not appear to be a difference between sign and speech in the attainment of each milestone.

For example, another important milestone of language acquisition, the use of two-word( / sign) combinations, seems to be attained at around 18 months for both signing and speaking children. Other later grammatical developments, such as the acquisition of verb agreement, also follow parallel time courses across the modalities. Let us consider another area in which the modality might be expected to have an impact on language acquisition: iconicity – a direct correspondence between form and meaning. As should be clear from our discussion so far, signs have internal phonological and morphological structure, and are not merely “pictures” of their referents. However, it is fair to say that some signs are iconically based, in that there is a motivated (non-arbitrary) relationship between the sign and its denotation. Similarly, some aspects of the grammar may be thought of as iconic in origin. One might suppose that these iconic elements may aid in the acquisition of sign language, and in this way distinguish between the acquisition processes in signing and speaking children. What does the research show? A clear example of non-arbitrary signed elements are the signs for “me” and “you”: these signs are made with pointing gestures which are essentially identical to the gestures made by hearing people when referring to first and second person, i.e., an index finger directed at one’s self or at the addressee. Since these indexic ASL signs are non-arbitrary, it might be expected that they would be particularly easy to learn, if the modality has an effect on language acquisition. However, it turns out that they are not. For some hearing children learning a spoken language, it is found that for a short period in early language development, the terms “me” and “you” get mixed up: the child uses “me” to refer to “you,” or “you” to refer to “me.” We can see why they might do this, since the referent for “me” or “you” changes depending on who is doing the talking. The child has to learn this peculiarity of these terms, and some children go through a stage of mixing them up. For the deaf child, since the forms used for ME and YOU are so transparent, it might be expected that no such errors would ever occur. However, some deaf children learning ASL make the same kind of mistake that some hearing children make: they confuse the signs for “me” and “you,” despite their iconicity. Studies involving other seemingly iconic aspects of the grammar have revealed similar countericonic errors in acquisition. A study by Richard Meier describes a child signing GIVE erroneously, in a sentence meaning “give the plate to him.” In the adult system, the verb agrees for the subject and the indirect object (i.e., the recipient), which is iconic with the real world activity of giving someone something. In the example, the child erroneously marks agreement with the direct object. He moves his hand toward the thing to be given, rather than the recipient – a gesture that seems iconically interpretable as “give something to the plate”. Here too, the child not only neglects to avail himself of iconic cues, he seems oblivious to them, focussing instead on the formal ingredients of the system – in this case, the reference points in the discourse. As in the acquisition of spoken language, the child acquiring sign language sometimes gets these formal elements mixed up. So, although it would seem that the iconicity in the visual modality would have a helpful effect on the process of language acquisition, we find that children do not seem to be attuned to certain obviously iconic aspects of signs. They are treating signs as abstract words, and thus they are not facilitated by iconicity in cases where one might expect them to be. They are simply progressing according to the universal timetable for language acquisition. Overall, studies of the acquisition of ASL in a number of deaf children have come to the conclusion that the natural acquisition of ASL is quite parallel to the natural acquisition of spoken language. In the end, it seems that the basics of ASL are acquired by deaf children by around the age of five years, just as in the acquisition of spoken language. This finding is quite important. For many years people thought that sound and sound patterning was a vital part of language, and that there could be no natural human language that did not rely on sound. The arguments for the linguistic status of American Sign Language are strongly supported by the finding that it is acquired naturally, taking a course that parallels that of spoken language. The idea of a biological timetable for language is also compatible with the idea that biology has its limits. Since Lenneberg (1967), it has been observed that there may be a “critical period” during which exposure to language is required in order for the natural mechanisms used for its acquisition to be triggered. Learning language after this period seems to be qualitatively different from early language acquisition, in a way that is sometimes interpreted as loss of the brain’s plasticity. Lenneberg used data about recovery after language loss due to traumatic or degenerative brain damage, and about second language learning, to argue that the critical period ends somewhere around puberty. Before that time, children can recover from aphasia or learn a second language much more easily than after this point. His proposal was strengthened by the study of isolated children such as Genie, a girl who was discovered at the age of 13 1 –2 after having been locked in a small room and not spoken to during her whole childhood. Genie was unable to learn many aspects of complex language even after her physical and mental condition were treated (Curtiss 1977). However, there are many questions about Genie’s situation and those of other isolated children, and fortunately these cases are rare – so few conclusions can be drawn about the critical age hypothesis from the study of delayed first language acquisition in normally hearing children. A unique opportunity for investigating the critical age hypothesis is presented by deaf children with hearing parents, however, because even in caring home environments, the age at which deaf children are exposed to sign language varies. Many deaf youngsters are not exposed to sign language at an early age, because their deafness is not diagnosed, or because their parents prefer to educate them in an oral-only manner, or simply because no one in the child’s environment uses sign language. In most cases, these children have no natural input to serve as a model for acquiring a spoken language, and their acquisition of sign language may begin as late as at the age of five, when they enter school, or perhaps even later. What, then, does sign language development in these children tell us about the critical period hypothesis? Here we may consider the gesture systems usually developed by young deaf children in the absence of a sign language model, often called “home sign”; the consequences of the late acquisition of conventional sign languages, where a model is only presented for the child in later childhood; and the birth of a new sign language in a new deaf community. In a series of extensive studies of these systems, Goldin-Meadow and colleagues have found that children systematically develop names for things, labels for actions, and ways to combine elements which are strikingly like those of real languages. The home sign systems are far from a fully developed language, but they share characteristics with language which tell us about its “resilience” (in Goldin-Meadow’s terms). As far as we know, there is no “Home Talk” – the circumstances for its development do not exist. Only the study of sign systems allows us to observe the in-born drive for language which creates some kind of formal system even in the complete absence of experience. Often, such children eventually are exposed to sign language and grow up to be adults who use it as their primary form of communication. How perfectly is the grammar of a sign language acquired when exposure to it begins after the critical period? In studies of adults who have used ASL for many years (e.g., Newport 1990) it has been found that the age at which exposure to language began is critical for the eventual acquisition of a complete grammar. Researchers find that even after 50 years of signing, people who were exposed to ASL only after the age of 13 systematically differ in their use of some of the complex mechanisms of ASL, as compared with similar-aged adults who acquired ASL from birth in signing homes. These later learners are fully expressive and use many of the same structures which the native learners use. However, their use of verbs of motion and location constructions as well as verb agreement, for example, is often very different. These results also support Lenneberg’s proposal that there is a critical period for language acquisition, in a way which would not have been discovered if not for the study of sign languages. The study of the development of a nascent sign language offers a unique perspective on the human language capacity and the critical age hypothesis. Research conducted by Judy Kegl, Ann Senghas, and their colleagues (e.g. Senghas 1995), has been charting the development of a new sign language in Nicaragua, where deaf people had been isolated from one another until 1979. At that time a school was established for deaf children, and a communication system of signs immediately began to develop spontaneously. The system that developed among the first group of signers is not fully conventionalized, and it is relatively simple in structure, much like spoken pidgins. The older children in Nicaragua had had no language model when they were at the critical age, so their communication remains pidgin-like. Over time, however, as children as young as four years old began to come to the school and take the pidgin system of the older children as a model, a more systematic and conventionalized language began to emerge in these younger signers. This language includes certain grammatical characteristics that have been found by linguists in established sign languages. This study shows that the human brain will create a communication system as soon as people congregate and have a need to communicate. Like creole studies in spoken language, it also shows that children have the capacity to further expand and regularize even relatively simple input and make it into a bona fide language.