Study title

Grammatical meaning is expressed by changes in word form (inflection): for example, in English, the ending -s is added to a verb form to show that it has a third person singular subject in the present tense. This is fairly simple. In other languages the systems are more intricate. In Spanish, the ending for 'we' in 'we sing' (cant-amos) differs from the one in 'we want' (quer-emos), which in turn differs from the one in 'we open' (abr-imos). Such inflectional classes are apparently useless: the variation is independent of meaning, and must simply be memorised. But these systems are widely found, highly structured, and remarkably resilient over time. They represent a unique sort of complexity with implications for theories of language and mind. Our knowledge of inflectional classes is largely limited to European languages. We move beyond this, focusing on the Oto-Manguean languages of Mexico, numbering about 200, many of which are threatened. They have a rich array of suffixes, prefixes, complex tonal patterns and stem alternations, co-occurring in a single word form. This results in the interaction of multiple layered inflectional classes, drastically increasing complexity. They provide important evidence of the degree of inflectional complexity a language can tolerate.