Rating the vitality of sign languages

The Expanded Graded Intergenerational Disruption Scale (EGIDS), developed by Lewis and Simons and based on work by Fishman, provides a means of rating 'language vitality' - the level of development or endangerment - where 'development' is understood as adding or preserving functions and 'endangerment' as loss of function. In its original form, it did not take sign languages into account. This paper explains what adjustments are needed to accommodate signed and spoken languages on an equal basis, recognising and generalising over the sociolinguistic differences in the two types of language communities. Besides minor wording changes made to avoid giving the impression that EGIDS applied only to spoken languages, we offer substantive changes to accommodate different patterns of intergenerational transmission; to better reflect the role of literacy, education, literature, institutional support, and standardisation in language development; and to reflect factors other than classic language shift which can undermine a language's vitality. Clarifications are made to the role of interpreters in rating a language's vitality, and in the definition of a language of wider communication. Several of these changes provide further insights into factors that affect the vitality of spoken languages.