Color discriminability makes over-specification efficient: Theoretical analysis and empirical evidence

A psychophysical analysis of referential communication establishes a causal link between a visual stimulus and a speaker’s perception of this stimulus, and between the speaker’s internal representation and their reference production. Here, I argue that, in addition to visual perception and language, social cognition plays an integral part in this complex process, as it enables successful speaker-listener coordination. This pragmatic analysis of referential communication tries to explain the redundant use of color adjectives. It is well documented that people use color words when it is not necessary to identify the referent; for instance, they may refer to “the blue star” in a display of shapes with a single star. This type of redundancy challenges influential work from cognitive science and philosophy of language, suggesting that human communication is fundamentally efficient. Here, I explain these seemingly contradictory findings by confirming the visual efficiency hypothesis: redundant color words can facilitate the listener’s visual search for a referent, despite making the description unnecessarily long. Participants’ eye movements revealed that they were faster to find “the blue star” than “the star” in a display of shapes with only one star. A language production experiment further revealed that speakers are highly sensitive to a target’s discriminability, systematically reducing their use of redundant color adjectives as the color of the target became more pervasive in a display. It is concluded that a referential expression’s efficiency should be based not only on its informational value, but also on its discriminatory value, which means that redundant color words can be more efficient than shorter descriptions.