The Nature of Verbs in Sign Languages: A Role and Reference Grammar account of Irish Sign Language Verbs

This paper is concerned with the special nature of sign language verbs, in particular to this research, Irish Sign Language verbs. We use Role and Reference Grammar to provide a definition of the structure of lexical entries that are sufficiently rich and robust in nature to represent Irish Sign Language verbs. Role and Reference Grammar takes language to be a system of communicative social action, and accordingly, analysing the communicative functions of grammatical structures plays a vital role in grammatical description and theory from this perspective. This work is part of research on the development of a linguistically motivated computational framework for Irish Sign Language. In providing a definition of a linguistically motivated computational model for Irish Sign Language we must be able to refer to the various articulators (hands, fingers, eyes, eyebrows etc.), as these are what we use to articulate the various phonemes, morphemes and lexemes of an utterance. Irish Sign Language is a visual gestural language. The fact that Irish Sign Language has no written or oral form means that, for us to represent an Irish Sign Language utterance in computational terms we must implement the use of a humanoid avatar capable of movement within threedimensional space. Here, we provide an account of the grammatical information that can be found within Irish Sign Language verbs. We use the Signs of Ireland corpus to access the relevant linguistic data pertinent to Irish Sign Language. Further to this we use ELAN software as an application tool, which allows us to view the corpus and collate relevant linguistic phenomena pertinent to Irish Sign Language. We utilise the Event Visibility Hypothesis in the development of our proposed lexicon architecture. The computational phonological parameters for Irish Sign Language manual features and non manual features are defined within a framework, which we refer to as the Sign_A framework, where the “A” within this The Nature of Verbs in Sign Languages: A Role and Reference Grammar account of Irish Sign Language Verbs TEANGA, Special Issue 11, pp. 67–99 68 title refers to Articulatory Structure Level. We leverage the Sign_A framework, and in particular, Articulatory Structure Level, in the development of a linguistically motivated computational definition of lexicon entries that are sufficiently robust in nature to represent ISL verbs within the Role and Reference Grammar lexicon. Keywords: Role and Reference Grammar; Generative Lexicon Theory; Sign_A framework Articulatory Structure Level; Event Visibility Hypothesis; Irish Sign language; Irish Sign Language Verbs 1. Introduction This paper is concerned with the investigation of the nature of sign language verbs and the architecture of Role and Reference Grammar (RRG) lexicon entries for SL verbs, in particular Irish Sign Language (ISL) verbs. We investigate the nature of ISL verbs and the challenges involved in the development of a lexicon entry that is capable of representing lexical information pertinent to ISL verbs. Sign Languages (SLs) are visual gestural languages articulated within gestural space (Rathmann & Mathur, 2002). SLs have no written form. ISL (O Baoill & Matthews, 2000; Leeson & Saeed, 2012) is a linguistically complete and very complex language. Communication occurs using a visual-gestural modality, encompassing manual and non-manual gestures. Manual gestures make use of hand forms, hand locations, hand movements and orientations of the palm. Non-manual gestures include the use of eye gaze, facial expression, head and upper body movements. Within the field of spoken language linguistics, a wealth of research has been carried out in relation to verb categorisation and classification. Levin (1993) provides a comprehensive taxonomy of over 3000 verbs from spoken English based on the properties of shared meaning and behaviour. He takes the view that the meaning of a verb affects its syntactic behaviour and he provides us with numerous verb classes by distinguishing verbs with similar syntactic behaviour. In relation to SLs, verb classification is traditionally described according to Padden’s (1998) classical tripartite classification of verbs based on American Sign Language (ASL), which has more recently been revisited (Meir et al. 2007). However, the tri-partite verb theory has been, in most cases, universally accepted. The Nature of Verbs in Sign Languages: A Role and Reference Grammar account of Irish Sign Language Verbs TEANGA, Special Issue 11, pp. 67–99 69 In this paper we provide an account of the grammatical information that can be found within ISL verbs. We provide an analysis of the Signs of Ireland (SOI) corpus (Leeson et al., 2006) and of the literature within the field in relation to the linguistic phenomena associated with ISL. Johnston and Schembri (2007, pp. 163–169) outline the difficulties involved in the analysis of SLs. With regard to our analysis of ISL verbs and data used, we look initially to the SOI corpus for data examples which allows us to provide still images of the phenomena together with a glossed example and the English translation. Where we use data from the SOI corpus we also provide a reference to the participant, the data source number and also location information. All of this information is provided by the SOI corpus. With regard to glossing, Pizzutto and Pietrandres (2011) identify the difficulties that can occur when glossing SL data with English tags. Taking this into account, we provide as many images from the original SOI data source as is possible due to illustrate the signed examples directly. Like Leeson and Saeed (2012), we follow Johnston (2001) in our approach to glossing. In an attempt to limit imposing variable lexical and grammatical information on the data, sentences were glossed using an ID-gloss for all variations of a single form. Where certain examples are particularly relevant, we also use literature from the field in the development of this framework, referencing them appropriately. We utilise the Event Visibility Hypothesis (EVH) (Wilbur 2008) in the development of our proposed lexicon architecture. We leverage Articulatory Structure Level (Murtagh, 2018) in the development of a linguistically motivated computational definition of lexicon entries that are sufficiently robust in nature to represent ISL verbs within the RRG lexicon. We utilise this newly proposed level of lexical representation, which describes the essential (computational) phonological parameters of an object as defined by the lexical item to cater specifically for the computational linguistic phenomena consistent with signed languages. These parameters will be used to account for various linguistic phenomena pertaining to ISL manual features (MFs) non manual features (NMFs), which are necessary to adequately represent ISL within our computational framework. We refer to our newly developed framework as the Sign_A framework, with the “A” within this term representing Articulatory Structure Level. We leverage our proposed Articulatory Structure Level for lexical meaning to accommodate the linguistic phenomena consistent with ISL and to develop a lexicon architecture capable of accommodating ISL in computational linguistic terms. The Nature of Verbs in Sign Languages: A Role and Reference Grammar account of Irish Sign Language Verbs TEANGA, Special Issue 11, pp. 67–99 70 2. Irish Sign Language ISL is a linguistically complete, rich and complex language. Communication within a sign language community occurs using the visual-gestural modality, encompassing MFs and NMFs. MFs include hand shapes, hand locations, hand movements and orientation of the palm of the hands. NMFs include the use of eye gaze, facial expression, mouthing, head and upper body movements. The visual gestural realisation of a word in SL involves the simultaneous and parallel expression of a varied number of MFs and NMFs, each with their own duration, orientation and relative configuration and movement. As discussed previously, verb classification within SL is traditionally described according to Padden’s classical tripartite classification of American Sign Language (ASL) verbs (Padden, 1988). The original theory has subsequently been re-visited, but Padden’s observation, which was in most cases universally accepted, is that SL verbs fall into one of three categories: plain verbs, spatial verbs and agreeing verbs. Padden initially named agreeing verbs as inflecting verbs but subsequently changed the term to agreeing verb. SL verb classes can be differentiated between depending upon the arguments that they encode. Not all SL verbs use a phonological shift in orientation or direction of movement to reflect a change semantically. According to Padden (1988) plain verbs are verbs that constitute the default semantic class. Plain verbs do not encode any grammatical features of their arguments. They do not encode morphological information for person and number by movement and do not show agreement with either subject or object. Plain verbs are uninflected and do not take agreement affixes. Agreeing verbs, which agree with the subject and/or object, are a class of verbs that denote transfer and are said to encode the syntactic role of the arguments, as well as their person and number features, via the direction of the movement of the hands and the orientation of the palms. Agreeing verb affixes show agreement with person or location. Spatial verbs are verbs that denote motion and location in space. Spatial verbs encode the locations of locative arguments (the source and the goal), based on the direction of movement of the hands. The shape of the path movement the hands are tracing often depicts the shape of the path that an object traverses in space. Figure 1 illustrates the three verb categories proposed by Padden (1988) in the tripartite theory of verbs. The Nature of Verbs in Sign Languages: A Role and Reference Grammar account of