Influences of posture on gravity perception in the audiovisual bounce inducing effect

Abstract

Visual perception is influenced by many factors including naturalistic motion that adheres to Newtonian principles of gravity. Previous research has examined perceptual interpretations of a classic cross-modal phenomenon – the audiovisual bounce-inducing effect (ABE) – and how it is influenced by gravity congruent motion. The ABE presents two identical objects with opposite trajectories moving in a downwards motion uniformly along diagonals where participants make stream vs bounce perceptual judgments. Perceptual interpretations of ABE vary depending on whether a sound is introduced at the point of coincidence of the two objects’ trajectories (i.e., sound increases ‘bounce’ percepts). These perceptual interpretations are also influenced by factors such as its congruency with Newtonian principles. The present study repeated a previous experiment that examined the effects of gravitational congruency on visual motion perception showing motion dynamics and congruency shift perceptual interpretations for accelerating motion events. In addition, our study altered the body’s posture (sitting/laying) so that the visual perception of movement was either congruent (sitting) or incongruent (laying) with Newtonian principles. We hypothesized that perceptual interpretations following gravity congruent perception would show a difference in the ‘bounce’ percept if the visual perception of downward motion is in the horizontal or vertical plane. Two identical discs moving in downward directions were presented to observers where the discs moved in uniform motion, acceleration, or deceleration. Sound was presented synchronously with point of coincidence or was absent, and each observer viewed these cross-modal events in both a sitting position and a laying position. Participants indicated via button press whether they perceived the discs to be streaming through or bouncing off each other. Our results show the impact of posture congruency with gravitational expectations on visual motion perception while observing different visual motion dynamics. These findings provide evidence of the complexity of factors that influence visual motion perception.