Decomposing unaccusativity: a statistical modelling approach.

While the two types of intransitive verbs, i.e., unergative and unaccusative, are hypothesised to be syntactically represented, many have proposed a semantic account where abstract properties related to agentivity and telicity, often conceptualised as binary properties, determine the classification. Here we explore the extent to which graded, embodied features rooted in neurobiological systems contribute to the distinction, representing verb meanings as continuous human ratings over various experiential dimensions. Unlike prior studies that classified verbs based on categorical intuition, we assessed the degree of unaccusativity by acceptability of the prenominal past participle construction, one of the unaccusativity diagnostics. Five models were constructed to explain these data: categorical syntactic/semantic, feature-based event-semantic, experiential, and distributional models. The experiential model best explained the diagnostic test data, suggesting that the unaccusative/unergative distinction may be an emergent phenomenon related to differences in underlying experiential content. The experiential model's advantages, including interpretability and scalability, are also discussed.