RESUMO
This study tested the influence of mood on the perception of the sitting affordance in two experiments. The objective of Experiment 1 was to evaluate participants' perception of the sitting affordance, without mood induction. Forty-three participants assessed their maximum sitting height (SHmax) from different seat heights (perceptual SHmax) before performing the action (motor SHmax). They accurately perceived the sitting affordance, in body-scaled intrinsic units. Indeed, participants all perceived they could sit as long as the seat height did not exceed 82% (perceptual πc) of their total leg length (L), while the actual value of this intrinsic relationship was 83% (motor πc). In Experiment 2, forty participants were subjected to a mood induction procedure before performing the task employed in Experiment 1. Neutral participants accurately perceived the sitting affordance, as their perceptual πc was equivalent to their motor πc. However, both joyful and sad participants had their perceptual πc significantly lower than their motor πc. These differences between mood groups were not explained by a variation in maximal effective action capabilities. Indeed, participants had equivalent motor πc, whatever their mood. Two interpretations are offered to explain how joyful and sad moods could influence the accuracy of affordance perception. The first is based on their potential effect on organism's energy level. The second is related to the disruption of participants' attunement to optical variables relevant for action guidance and/or to perceptual-motor calibration.