Investigating the Uniform Information Density hypothesis with complex nominal compounds

The Uniform Information Density (UID) hypothesis proposes that speakers communicate by transmitting information close to a constant rate. When choosing between two syntactic variants, it claims that speakers prefer the variant distributing information most evenly, avoiding signal peaks and troughs. If speakers prefer transmitting information uniformly, then comprehenders should also prefer a uniform signal, experiencing difficulty whenever confronted with informational peaks. However, the literature investigating this hypothesis has focused mostly on production, with only a few studies considering comprehension. In this study, we investigate comprehension in two eye-tracking experiments. Participants read sentences of two different lengths, reflecting different degrees of density, containing either a dense structure (a nominal compound, NC) or a structure that spreads the information through more words (a noun followed by a prepositional phrase, PP). Favoring the UID hypothesis, participants gazed longer at text segments following the critical structure when it was an NC than when it was a PP. They also regressed more in sentences containing longer structures. However, the pattern of results was not as clear as expected, potentially reflecting participants’ experience with the denser structure or task differences between production and comprehension. These aspects should be taken into account in future research investigating the UID hypothesis for comprehension.