thumb|right|Picture of a Home Sign gesture
Home sign (or kitchen sign) is a gestural communication system, often invented spontaneously by a deaf child who lacks accessible linguistic input.
Because home sign systems are used regularly as the child's form of communication, they develop to become more complex than simple gestures. Though not considered to be a complete language, these systems may be classified as linguistic phenomena that show similar characteristics to signed and spoken language. Home sign systems display significant degrees of internal complexity, using gestures with consistent meanings, word order, and grammatical categories. Linguists have been interested in home sign systems as insight into the human ability to generate, acquire, and process language.
- do not have a consistent meaning-symbol relationship (although later research has challenged this claim),
- do not pass on from generation to generation,
- are not shared by one large group,
- and are not considered the same over a community of signers.
However, there are certain "resilient" properties of language whose development can proceed without guidance of a conventional language model. More recent studies of deaf children's gestural systems show systematicity and productivity. Across users, these systems tend to exhibit a stable lexicon, word order tendency, complex sentence usage, and noun-verb pairs. They have also been shown to have the property of recursion, which allows systems to be generative. Deaf children may borrow spoken language gestures, but these gestures are altered to serve as linguistic markers. As the child develops, their utterances grow in size and complexity. Adult home signers use systems that mature to display more linguistic features than the simpler systems used by child home signers.
Lexicon
Studies of home signing children and adults show consistent pairing between the form of a gesture token and its meaning. These signs are also combined in compound gestures to create new words. A study of adult home signers in Nicaragua show that home signers use gestures to communicate about numbers, with cardinal numeral and non-cardinal numeral markings.
Morphology
Home sign systems have simple morphology. Gestures are composed of parts with a limited set of handshape forms. Home signers also use handshape as a productive morphological marker in predicates, displaying a distinction between nominals and predicates. Study of adolescent home signers show ability to express motion events, though this strategy differs from conventional sign language. The motions of signs used in home sign systems can vary in length of path and directionality. Most of the hand shape morphemes could be found in combination with more than one motion morpheme, and vice versa. Home signers mark grammatical subjects in sentences and are able to distinguish the subject from the topic of the sentence. These systems show some evidence of a prosodic system for marking phrase and utterance boundaries.
Narratives
Home signing children vary greatly in how often they display narrative skills; however, their narratives show similar structural patterns. This includes elaborating on basic narrative by including setting, actions, a complication, and temporal order. Hearing mothers produce co-narration with deaf children less frequently (than hearing mothers do with hearing children), and these contributions are spoken and rarely gestural.
Conditions for emergence
The context of home sign system creation includes limited or no exposure to a spoken or signed language model, isolation from deaf children and adults, and parental choices regarding communication with the deaf child. Home sign creation is a common experience of deaf children in hearing families, as approximately 75% of hearing parents do not sign and communicate with their deaf children using a small set of gestures, speaking, and lipreading. In contrast, in a home with parents who are deaf or know sign language, a child can pick up the sign language in the same way a hearing child can pick up spoken language.
Social network structure influences the development of a home sign system, impacting the conventionalization of referring expressions among members. Richly connected networks, where all participants interact with one another using the communication system, show greater and faster conventionalization. Home sign systems are typically sparsely connected networks, where the home signer communicates with each member of the network but the members do not use home sign to communicate with each other.
Impact of lacking a language model
Studies by Deanna Gagne and Marie Coppola of perspective-taking abilities in adult home signers reveal that home signers do not pass experimental false-belief tasks, despite having visual observation of social interaction. False-belief understanding, integral to the development of theory of mind, requires lots of language experience and linguistic input. Further study of these adult home signers indicates that home signers show precursor abilities for theory of mind, such as visual perspective taking.
Lack of conventional language for numbers has been shown to affect numerical ability. In comparison to unschooled hearing and signing deaf individuals, adult home signers do not consistently produce gestures that accurately represent cardinal values of larger sets and do not exhibit effective use of finger counting strategies. Further study indicates home signers are able to recall gestures used as nouns, verbs, and adjectives, but they show poor number recall, which worsens as numbers increase.
Cross-cultural comparisons
Syntactic structure is similar between groups of home signers in different cultures and geographical regions, including word order preferences and complex sentence usage. For example, home sign systems of children in Turkey and the United States exhibit similar patterns in sentence-level structure.