This paper investigates the occurrence of inflected predicative adjectives, an optional yet distinguishing feature of German dialects spoken in southern Switzerland. We provide an in-depth analysis of the patterns of change of this morphosyntactic marker with a particular focus on extralinguistic factors. Historical records from 1950 were compared to contemporary data collected from 192 speakers across 49 localities in 2020–21. Our results corroborate previous reports indicating a substantial, real-time decline in inflected forms. Logistic mixed-effects modeling suggests that the inflection of predicative adjectives occurs more frequently among speakers who report tight social networks, have a strong local dialect identity, and regularly use one or more Romance languages. These findings support the claim that tight social networks and local dialect identity construction may lead to the preservation of conservative grammatical forms. Additionally, the effect of Romance languages highlights the role of transfer phenomena induced by language contact.
