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

The eyebrows are used as conversational signals in face-to-face spoken interaction (Ekman, 1979). In Sign Language of the Netherlands (NGT), the eyebrows are typically furrowed in content questions, and raised in polar questions (Coerts, 1992). On the other hand, these eyebrow positions are also associated with anger and surprise, respectively, in general human communication (Ekman, 1993). This overlap in the functional load of the eyebrow positions results in a potential conflict for NGT signers when combining these functions simultaneously. In order to investigate the effect of the simultaneous realization of both functions on the eyebrow position we elicited instances of both question types with neutral affect and with various affective states. The data were coded using the Facial Action Coding System (FACS: Ekman, Friesen, & Hager, 2002) for type of brow movement as well as for intensity. FACS allows for the coding of muscle groups, which are termed Action Units (AUs) and which produce facial appearance changes. The results show that linguistic and affective functions of eyebrows may influence each other in NGT. That is, in surprised polar questions and angry content question a phonetic enhancement takes place of raising and furrowing, respectively. In the items with contrasting eyebrow movements, the grammatical and affective AUs are either blended (occur simultaneously) or they are realized sequentially. Interestingly, the absence of eyebrow raising (marked by AU 1+2) in angry polar questions, and the presence of eyebrow furrowing (realized by AU 4) in surprised content questions suggests that in general AU 4 may be phonetically stronger than AU 1 and AU 2, independent of its linguistic or affective function.