Evidence for Availability Effects on Speaker Choice in the Russian Comparative Alternation

When a language offers multiple options for expressing the same meaning, what principles govern a speaker's choice? Two well-known principles proposed for explaining wide-ranging speaker preference are Uniform Information Density and Availability-Based Production. Here we test the predictions of these theories in a previously uninvestigated case of speaker choice. Russian has two ways of expressing the comparative: an \textsc{explicit} option (\textit{Ona bystree chem ja}/She fast{\sc-comp} than me{\sc-nom}) and a \textsc{genitive} option (\textit{Ona bystree menya/She fast{\sc-comp} me{\sc-gen}}). We lay out several potential predictions of each theory for speaker choice in the Russian comparative construction, including effects of post-comparative word predictability, phrase length, syntactic complexity, and semantic association between the comparative adjective and subsequent noun. In a corpus study, we find that the explicit construction is used preferentially when the post-comparative noun phrase is longer, has a relative clause, and is less semantically associated with the comparative adjective. A follow-up production experiment using visual scene stimuli to elicit comparative sentences replicates the corpus finding that Russian native speakers prefer the explicit form when post-comparative phrases are longer. These findings offer no clear support for the predictions of Uniform Information Density, but are broadly supportive of Availability-Based Production, with the explicit option serving as an unreduced form that eases speakers' planning of complex or low-availability utterances. Code for this study is available at https://github.mit.edu/thclark/russian_ui