Linguistic typology in the past decades has questioned whether parts of speech such as nouns and verbs are universal across different languages (e.g., Haspelmath, 2001; Evans & Levinson, 2009). Similarly, there is an ongoing debate in theoretical linguistics and psycholinguistics as to whether (major) categories such as noun and verb (i) constitute lexical primitives, (ii) result from a combinatorial syntactic process, or (iii) emerge only in the context of language use (Halle & Marantz, 1993; Vigliocco et al., 2011). Our project starts from the observation that word class universals like noun and verb are not always clearly distinguished in sign language. Here we take German Sign Language (DGS) as an empirical testing ground. Similar to spoken languages, e.g., English (the book vs. to book), many signs in DGS seem to be ambiguous insofar as their lexical status depends on the (syntactic) context in which they are produced. Preliminary studies on sign languages, however, have observed that sign languages exhibit a tendency to mark nouns and verbs by manual and probably also by nonmanual phonological modifications of the root (e.g., Supalla & Newport, 1978).
Our project investigates the distinction between major word classes in DGS using different linguistic and neuroscientific methods focusing on language production as well as single sign and sentence processing. Furthermore, within the analysis of the overt realisation of the noun-verb-distinction in DGS, we investigate the linguistic and cognitive relevance of parts of speech and the impact of iconicity on sign languages. Our aim is therefore threefold: (i) We want to test the supposed universality of the noun-verb-distinction, by going beyond previous work done on spoken languages. We will explore differences in the distribution of the two lexical categories in DGS, a language in the visuo-spatial modality, using linguistic, behavioral, and neuroscientific experiments. (ii) We want to provide insights into the iconic properties of DGS and how these are perceived by deaf and hearing people, thereby identifying tendencies that are not necessarily linguistic but could – due to their iconic nature – be grounded in non-linguistic cognition. This will be explored using qualitative as well as data-driven approaches that will investigate iconic properties and motivations of signs in DGS and how iconicity is linked to the overt realisation of the noun-verb-distinction. (iii) We want to match the empirical findings of our studies with recent formal and functional analyses of parts of speech as lexical or syntactic categories thereby contributing to a better theoretical understanding of parts of speech and the impact of modality on parts of speech.