Implications of Sign Language Acquisition

The study of sign language has become increasingly of interest to linguists, as it examines how language is conceptualized by those who are unable to acquire spoken language. Sign languages feature many of the same nuances as spoken languages, a fact that has become a focal point for linguists who debate the extent to which language is innate. Many use data on sign language to argue that humans have language-specific abilities.

Milestones in sign language acquisition mirror those of spoken language. Deaf children go through the same phases of acquisition attributed to hearing children. There is ample proof that sign language is conceptualized as language, rather than just communicative gestures; in fact, deaf children use communicative gestures as often as hearing children, their signing remaining separate from them.(1)

Deaf children born to hearing parents are prone to create their own communication system, known as homesign, in order to effectively communicate. These homesign languages have morphology, syntax, nouns, verbs, and adjectives—despite the fact that these children have no linguistic input.(2)

Aphasia studies with deaf signers have shown that damage to specific areas of the brain has the same effect on syntactic and lexical retrieval as it does in language speakers.(3) This information is crucial, as it shows that language does not have to be acquired aurally—and that the same structures applied to spoken language are also used in non-spoken language. Nativists argue that this grants validity to Chomsky’s idea of a Language Acquisition Device (LAD) in the brain that is hard-wired to process and create language.

Syntactic Structures in American Sign Language (ASL)

Word Order
Early signers tend to have a more rigid word order in order to convey syntactic relations, whereas adult signers who have gained more complex morphology showcase more fluid word order. This word order fluidity has led some linguists to claim that ASL does not have word order, though it does feature a basic subject-verb-object word order and hierarchical structures. (4, 5) Just as in English, ASL can topicalize (an emphatic reordering of words and phrases, like "John Mary loves") and make other various changes to word order. Often these changes are indicated with "nonmanual markings," such as head tilt and eye gaze in order to indicate subject-verb agreement and conceptually link clauses together.(5) However, without these nonmanual markings, the standard word order is SVO.(4)

Except for prepositional phrases, which are not used in ASL as location and noun relationships are conveyed with verbs and morphology respectively, ASL has the same phrases as in English.(4) Constraints on topicalization prove the conceptual existence of these phrases, as entire clauses can be topicalized instead of partial clausal components; compare "*Henchman, Sam Spade insulted the fat man's" to "The fat man's henchman, Sam Spade insulted."(6)

ASL is characterized by tense phrases (TP) with tense markers occurring before the verb phrase (VP). Though this would point to a c-command relationship between tense and action, negation methods in ASL most clearly exemplify the concept of c-command: instead of using a negation sign (accompanied with nonmanual markings like furrowed eyebrows or a side-to-side head-shake), a signer may use nonmanual negation along with a VP, having the same effect. However, it is ungrammatical to sign a negative without the nonmanual negation, and nonmanual negation cannot be used outside of the head VP--showing that the same notions of c-command relationships within hierarchical structures exist in ASL.(5)

from The Syntax of American Sign Language

Determiner phrases/noun phrases (DP/NP) feature both definite and indefinite determiners, adjectives (used after, not before, the noun), possessive constructions, pronouns, and locative adverbial phrases (e.g. "the man way over there").(5) The extent to which these are expressed are not always manual, and may be expressed through nonmanual markers. These nonmanual markers serve to identify clause boundaries. For instance, the definite eye gaze when used with a NP must be used for the entirety of the phrase if there is no definite sign used. Therefore, using the definite gaze just for "car" in the phrase "blue car" is ungrammatical.

from The Syntax of American Sign Language
from The Syntax of American Sign Language

Homesigns and World Sign Languages

During the two-word stage for deaf signing children, verbs are almost exclusively put at the end of the utterance after the subject. If the utterance is transitive, the object is put after the verb. Many home signs therefore end up in a subject-verb-object form. Often, however, when these children do finally learn a sign language and become morphologically competent, word order becomes less relevant; second-generation learners of sign language do not follow this rigid pattern.(7)

Nicaraguan Sign Language
In the 1970s and 1980s, Nicaragua underwent education reform that for the first time created institutions of learning for the deaf. Children that were previously using homesign with their immediate family were instead having to communicate with others. A standardized sign language quickly began to form, creating a creole that become more and more nuanced over time. As with any acquisition, the younger the child was when exposed to this burgeoning language, the more competent they were with it. This rapid creolization is of a particular focus for linguists, as it provides insight into how children process and conceive of their languages.(8)

Al-Sayyid Bedouin Sign Language
A recessive trait specific to a particular community in southern Israel causes pre-linguistic deafness, resulting in a small, isolated community of signers. This language developed independently of its surrounding languages as evidenced by its different word order and negation system. Study of this language is significant as it shows yet another sign language where "a conventionalized pattern emerges for relating actions and events to the entities that perform and are affected by them, a pattern rooted in the basic syntactic notions of subject, object, and verb or predicate."(7) This shows that humans have a natural inclination to organize their communication along grammatical lines.

[1] Pettito, L.A. (2000). Biological Foundations of Language.
[2] Zheng, M. and Goldin-Meadow, S. (2002). Thought before language: how deaf and hearing children express motion events across cultures. Cognition 85.
[3] Bellugi U, Poizner H, and Klima E.S. (1983). Brain organization for language: clues from sign aphasia. Human Neurobiology 2(3). Link.
[4] Newport, E.L. and Meier, R.P. (1985). The Acquisition of American Sign Language. The Crosslinguistic Study of Language Acquisition, Volume 1: The Data.
[5] Neidle, C., Kegl, J., MacLaughlin, D., Bahan, B., and Lee, R.G. (2000). The Syntax of American Sign Language: Functional Categories and Hierarchical Structure.
[6] Fromkin, V., Rodman, R., and Hyams, N. (2011). An Introduction to Language, 9th ed.
[7] Sandler, W., Meir, I., Padden, C., Mark Aronoff, M. and Jeremy A. Sabloff, J.A. (2005). The Emergence of Grammar: Systematic Structure in a New Language.Proceedings of the National Academy of Sciences of the United States of America 102(7)
[8]Senghas, R., Senghas, A., and Pyers, J.E. (2005). The Emergence of Nicaraguan Sign Language: Questions of Development, Acquisition, and Evolution. Biology & Knowledge Revisited: From Neurogenesis to Psychogenesis.