The In-out Effect: Examining the Role of Perceptual Fluency in the Preference for Words with Inward-wandering Consonantal Articulation

Words whose consonantal articulation spots wander inward, simulating ingestion movements, are preferred to words featuring the opposite consonantal articulation direction, that is, resembling expectoration movements. The underlying mechanism of this so-called in-out effect is far from settled. Contrary to the original explanation proposing an oral approach-avoidance mechanism, recent evidence has been used to support an oral motor-fluency mechanism, suggesting that inward words are preferred because they may be more common and/or easier to pronounce. Across six experiments (n = 1123), we examined the impact of different fluency sources in the emergence of the in-out effect. The preference for inward-wandering words persisted both with classical font type and figure-ground contrast fluency manipulations, and no systematic additive effects were observed. The in-out effect was also replicated for the first time with a between-participant design. These results suggest that the in-out effect may be permeable to fluency manipulations, but it is not dependent upon a plain fluency mechanism.