Behavioural evidence for implicative paradigmatic relations

Form predictability has long been known to influence speaker behaviour in language learning and use. However, this observation has largely remained dissociated from the question of the most apt theoretical framing of the effects observed. We set out to seek evidence that speakers' relationship to form predictability is best characterised in paradigmatic terms: in an experimental task comparable to prediction of one word form from a related one, speakers appear sensitive to the probabilistic, implicative relations that make up a morphological paradigm. We find this effect to be omnidirectional, from any paradigm cell to any paradigm cell. Form predictability does not impact speaker behaviour in a vacuum, but instead works together with aspects of memory and learning to organise the mental lexicon and inform language use. In a corpus study, we map out the complex relationships that exist between paradigmatic form predictability, lexeme frequency and cell frequency in the context of naturalistic language use. Speakers appear to exploit all available probabilistic relationships between the word forms of a language in a way that is predicted by Word and Paradigm theories of morphology, with memory and predictive processing playing a mediating role in all aspects of language use.