Abstract

Language endangerment and extinction are phenomena that affect millions of people across the world. However, since academics began acknowledging them about 100 years ago, by and large only spoken languages were considered. The notion of sign language endangerment was almost entirely absent. Addressing this gap, this synoptic commentary draws together four articles that examine the possible causes of sign languages’ vigour and/or decline. The articles refer to these potential causes as ‘factors’, for example governmental policies, generational language use, and the community's attitudes toward their own sign language. This ‘factor approach’ is drawn from research into spoken languages. This synoptic commentary reflects on the implications of quantifying language vitality in this manner. It highlights the tension between the practical need to assess endangerment levels for policy advocacy and the dangers of oversimplifying or misunderstanding language vitality. The factor approach is explored in terms of how it has shaped the trajectory of research into sign language vitality. Its possible future is highlighted in view of the increased prevalence of artificial intelligence, which was not yet in common use when the papers were written. Overall, this PhD by Published Work has resulted in an original contribution to knowledge by showing for the first time how to adapt a model that was developed for spoken languages to assess the vitality of sign languages, and deploying new methodological innovations such as a system of averaged scores devised by an international committee with both deaf and hearing members. It also presents components of a deaf-centred approach to language vitality research in a theoretical model. Finally, the PhD gives the first peer-reviewed, published account of the utility of an interactive atlas for assessing sign language vitality.