Neuropsychological Studies of Linguistic and Affective Facial Expressions in Deaf Signers

Abstract

For deaf users of American Sign Language (ASL), facial behaviors function in two distinct ways: to convey affect (as with spoken languages) and to mark certain specific grammatical structures (e.g., relative clauses), thus subserving distinctly linguistic functions in ways that are unique to signed languages. The existence of two functionally different classes of facial behaviors raises questions concerning neural control of language and nonlanguage functions. Examining patterns of neural mediation for differential functions of facial expressions, linguistic versus affective, provides a unique perspective on the determinants of hemispheric specialization. This paper presents two studies which explore facial expression production in deaf signers. An experimental paradigm uses chimeric stimuli of ASL linguistic and affective facial expressions (photographs of right vs. left composites of posed expressions) to explore patterns of productive asymmetries in brain-intact signers. A second study examines facial expression production in left and right brain lesioned deaf signers, specifying unique patterns of spared and impaired functions. Both studies show striking differences between affective and linguistic facial expressions. The data indicate that for deaf signing individuals, affective expressions appear to be primarily mediated by the right-hemisphere. In contrast, these studies provide evidence that linguistic facial expressions involve left hemisphere mediation. This represents an important finding, since one and the same muscular system is involved in two functionally distinct types of facial expressions. For hearing persons, the right-hemisphere may be predominant in affective facial expression, but for deaf signers, hemispheric specialization for facial signals is influenced by the purposes those signals serve. Taken together, the data provide important new insights into the determinants of the specialization of the cerebral hemispheres in humans.

Scope-taking strategies and the order of clausal categories in German Sign Language

“…NMMs can, on a more traditional account, serve several different functions, some of which are non-linguistic in nature and some linguistic. Non-manuals serving nonlinguistic functions, i.e., affective gestures for expressing emotions, are clearly different from linguistic uses, in that the non-linguistic NMMs are processed in the right hemisphere (Corina 1989;Kegl & Poizner 1991;Poizner & Kegl 1992;Loew, Kegl & Poizner 1997;Corina, Bellugi & Reilly 1999) and differ in how they are acquired by children (e.g., Reilly, McIntire & Bellugi 1990). Most importantly, however, non-linguistic NMMs do not have strict temporal alignment restrictions vis-à-vis the onsets and offsets of manual signs (Baker-Shenk 1983;Emmorey 1999;Wilbur 2003).…”

The interaction of eye blinks and other prosodic cues in German Sign Language

“…Furthermore, the two types of nonmanuals are processed in different neuronal areas. For a neuropsychological distinction of affective and grammatical nonmanual features see Corina et al (1999). and a few other sign languages that have been investigated so far (cf.…”

Mixed Signals: Combining Linguistic and Affective Functions of Eyebrows in Questions in Sign Language of the Netherlands

“…4 The Edinburgh non-manual coding system (ENCS) was developed by Colville, Denmark, Mason, Denmark, & Brennan (1984) in order to code for actions in signed communication that are not produced by the hands. Although the same muscles (AUs) are used in affective and linguistic use of eyebrows, it has been argued that they are distinct in their formal properties such as scope, onset, and apex (Corina, Bellugi, & Reilly, 1999;Wilbur, 2003). First of all, while linguistic facial signals are hypothesized to align with phrasal boundaries within the signed sentence, affective facial signals may spread over longer periods of conversation and not line up strictly with phrasal boundaries.…”