The evolution of morphosyntactic categorization: Formal typology, diachrony, and comparative reconstruction of the mental lexicon

Linguistic categories serve as cognitive tools for humans to organize, understand, and navigate the complex world around them. Categorizers - elements that formally mark lexical categories such as nouns, verbs, and adjectives - belong to the core building blocks of the mental lexicon. However, it is still unclear how and why new categories and categorizers arise and how their function changes over time. Bridging the gap between disciplines, the EVOCAT project aims to unravel this puzzle by uncovering the underlying principles that govern the formation, representation, and evolution of linguistic categories. Based on a large-scale quantitative and qualitative analysis of categorization morphology in the ancient Indo-European (IE) languages and their descendants, EVOCAT’s goal is to uncover how categorizers shape the mental lexicon, how they change over time, and how their evolution can be exploited for the purposes of phylogenetic reconstruction. The project's core hypothesis is that the rise and development of new categorizers proceeds via strictly directional reanalysis of morphological material, which predicts that categorizers develop in a uniform manner cross-linguistically and that this development gives rise to meaningful isoglosses that distinguish different subbranches of related languages from one another. This hypothesis will moreover be tested against data from non-IE languages with a comparable time span of attestation to show that it truly holds cross-linguistically. Discovering regularities and establishing universals in the domain of the mental lexicon will lead to ground-breaking insights into the nature of the categorial building blocks of human grammar. This ambitious project will provide the crucial empirical and theoretical basis for further research at the interface of language change, comparative reconstruction, linguistic theory, and psycholinguistics, and ultimately for our understanding of a core aspect of the human language faculty.