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

When speakers refer to objects in the world, they frequently overinform their listener. 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 Experiment One (N = 72), we borrow methods from psychophysics to evaluate this hypothesis across attributes (material, colour) and sensory modalities (audition, vision). We show that across attributes and modalities, speakers ground reference in perceptual attributes that facilitate their listeners’ referential search. In Experiment Two (N = 97), we find that search efficiency cannot account for speakers’ disproportionate use of colour in reference. We show that reference to colour remains disproportionate even when we control colours’ advantages in attention-capturing effects, modality, perceptual salience, word production and retrieval effort. We therefore conclude that the centrality of colour’s search efficiency in the immediate environment: Colour is special.