Linguistics Stack Exchange is a question and answer site for professional linguists and others with an interest in linguistic research and theory. It only takes a minute to sign up.
Sign up to join this community
Apart from manuals, also nonmanuals; such as head tilt or head shake have grammatical features in Turkish sign languages. They appear while asking questions or giving negation.
Some lip movements are seen while people sign. I know that they do this to ease the convention of the meaning for their hearing counterparts while communicating. But I wonder whether they have further function or not.
Do you know any research carried about this topic? Please provide citations and references.
Since you specified about the TID1 in the comments, I made a search specifically about it. What I found is a paper titled "Aspects of Türk İşaret Dili" by Ulrike Zeshan, which analysis various features of the Turkish Sign language.
In the paragraph "2.2 Types of nonmanual negation"2, the author address various ways of negating using methods that don't include hand signing: head movements and facial expressions.
Concerning the second, which is what we're interested in there is something about the use of the mouth (emphasis mine):
Whereas both the negative headshake and the backward head tilt are very common in TID, a third nonmanual signal that can convey negation is rather marginal in the language, yet nevertheless very interesting. In some rather rare contexts that still need to be specified, a puff of the cheeks with subsequent release of the air trapped in the mouth has a negative meaning (Figure 8 and videoclip 6). Moreover, the signal carries its negative meaning even in the absence of a manual negator sign, that is, it is sufficient to negate a clause by itself. In the following example, it is repeated because the predicate it co-occurs with also has repeated movement.
Then it continues:
The use of this nonmanual signal is interesting because, to the best of my knowledge, facial expressions have not been shown to function as negators on their own. Various facial expressions, such as frowning or pulling down the corners of the mouth, do accompany negation in many sign languages (e.g. Bergman 1995 for Swedish Sign Language, Coerts 1992 for Sign Language of the Netherlands, Berthiaume & Rinfret 2000 for Langue des Signes Québécoise). However, it is often unclear whether they should be considered grammatical or affective facial expressions. In any case, they always occur in addition to some other manual or nonmanual marking of negation, not as the sole marker of negation as in the above example from TID. [...]
Up to this point I still had some doubts but another paper, concerning facial expressions recognition, "Facial feature tracking and expression recognition for sign language" by İsmail Arı, about the previous work said that3:
Sign language expressions are performed with the combination of manual (hand gestures) and non-manual components (facial expressions, head motion and pose, body movements). Some expressions are performed only using hand gestures whereas some change the meaning where a facial expression accompanies hand gestures. For example, in Turkish Sign Language (TSL), a sentence can be in positive, negative and question clause forms if the hand gesture of the verb is accompanied by different non-manual gestures as Zeshan [35] describes in her work on TSL. [...]
So I'd say that facial expressions certainly provide a suprasegmental and grammatical feature too, although this doesn't make them part of the sign. In other words, a sign's meaning is not incomplete without these nonmanual gestures, unless you need to provide some grammatical feature (negation, question, etc.).
1: Turkish Sign Language in Turkish: "Türk İşaret Dili". I'll refer to it using TID.
2: Page 58.
3: Chapter 1.2.5. Facial Expression Classification in the Scope of Sign Language Expressions, page 11.
My previous answer (see edit history) concerned signed languages generally, as they all form content words (eg. nouns, verbs, ) with the hands and use facial expression and body movements to form grammatical function words as in Alenanno's example, adverbial “not” formed by puffed cheeks, or my example, the complementizer “that” that signals a relative clause and takes the form of a raised lip in both ASL and TID.
“[relative clause] constructions are accompanied by special non-manual markers: tensed cheeks and tensed upper lip”
From a lecture "Relative Clause Constructions in Turkish Sign Language” given by Okan Kubus at the Nijmegen Gesture Centre, 2 February 2011: Max Planck Institute for Psycholinguistics.
These uses of the mouth are part of TID grammar and are distinct from mouthing words of spoken Turkish while signing TID. (My gestures when speaking English are often signs from ASL, but no one suggests these are part of English.)
Those mouthed words can be borrowed, sort of. Non-visible phonetic features like voicing or velarization obviously won't be, but any visible features of spoken words can be borrowed into the signed language if they don't interfere with the grammatical usage discussed above. In that case the borrowed features will change to conform with the regular phonological constraints of the borrowing signed language, and may end up looking totally unlike the original spoken word, and may become an obligatory part of the lexical sign.
This lexical use of mouth movements are also distinct from the grammatical usage above. Zeshan, cited above, gives an example.
The sign ‘Deaf’ is used in combination with two different mouthings that both consist of two Turkish words coordinated with the double contact of the index finger at the corner of the mouth and then at the ear. The first mouthing, /sag ˘ır dilsiz/ ‘deaf dumb’ (lit. ‘deaf without-tongue/language’) is the older, more traditional term, whereas younger people, under the influence of more recent political correctness, often use the term /is¸itme engelli/ ‘hearing impaired’ instead. (page 48)
Here we see a lexical, not grammatical, use of mouthing: two forms of a TID word whose meaning, “deaf”, is distinct from either of the Turkish substrate phrases that contributed to it. In English, Turkish or TID, the word's meaning “deaf” is complete, and if you want to say “not deaf” you add the grammatical function word, /not/, /degil,/ or /puffed cheeks/, respectively.
Here is a whole book on this topic
Boyes-Braem, Penny, and Sutton-Spence, Rachel eds. 2001. The Hands are the Head of the Mouth: The Mouth as Articulator in Sign Languages. International Studies on Sign Language and Communication of the Deaf ; 39. Hamburg: Signum Verlag.
