Reference Production Facilitates Listener Search Across Modalities, but Colour is Special

When speakers refer to objects in the world, they frequently overinform their listener by providing redundant adjectives. Contrary to classical theories in linguistics, we hypothesise that overinformativeness is an efficient means of facilitating listener comprehension: Speakers use redundancy to provide their listener with search-efficient perceptual information. In two experiments (total N = 174), we borrow methods from psychophysics and the literature on visual search to evaluate this hy-pothesis across three attributes (material, orientation, colour) and two sensory modalities (auditon, vision). We show that across attributes and across modalities, speakers ground reference in perceptual attributes that are highly likely to facilitate their listeners’ referential search. Contrary to our expectations, we also find that search efficiency cannot completely account for speakers’ disproportionate use of colour in reference, even when we control colours’ potential advantages in modality, ease of discrimination, perceptual salience, and word production and retrieval effort. We therefore conclude that the centrality of colour in reference extends beyond colours’ perceptual salience, perceptual discriminability, and general search efficiency in the immediate environment: Colour is special.