Abstract
This paper discusses the role of cognitive factors in language change; specifically, it investigates the potential impact of argument ambiguity avoidance on the emergence of one of the most well-studied syntactic alternations in English, viz. the dative alternation (We gave them cake vs We gave cake to them). Linking this development to other major changes in the history of English like the loss of case marking, I propose that morphological as well as semantic-pragmatic ambiguity between prototypical agents (subjects) and prototypical recipients (indirect objects) in ditransitive clauses plausibly gave a processing advantage to patterns with higher cue reliability such as prepositional marking, but also fixed clause-level (SVO) order. The main hypotheses are tested through a quantitative analysis of ditransitives in a corpus of Middle English, which (i) confirms that the spread of the PP-construction is impacted by argument ambiguity and (ii) demonstrates that this change reflects a complex restructuring of disambiguation strategies.