The influence of visual flow and perceptual load on locomotion speed

Casimir J H Ludwig,Kate L Howard,Nicholas Alexander,Isha Mundkur,Alicja A Jedrzejewska,David Redmill

doi:10.3758/s13414-017-1417-3

Casimir J H Ludwig, Kate L Howard + Show 4 more

Open Access

https://doi.org/10.3758/s13414-017-1417-3

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Abstract

Visual flow is used to perceive and regulate movement speed during locomotion. We assessed the extent to which variation in flow from the ground plane, arising from static visual textures, influences locomotion speed under conditions of concurrent perceptual load. In two experiments, participants walked over a 12-m projected walkway that consisted of stripes that were oriented orthogonal to the walking direction. In the critical conditions, the frequency of the stripes increased or decreased. We observed small, but consistent effects on walking speed, so that participants were walking slower when the frequency increased compared to when the frequency decreased. This basic effect suggests that participants interpreted the change in visual flow in these conditions as at least partly due to a change in their own movement speed, and counteracted such a change by speeding up or slowing down. Critically, these effects were magnified under conditions of low perceptual load and a locus of attention near the ground plane. Our findings suggest that the contribution of vision in the control of ongoing locomotion is relatively fluid and dependent on ongoing perceptual (and perhaps more generally cognitive) task demands.

Highlights

Visual flow is an important perceptual cue that may be used in starting, stopping, and ongoing control of human and non-human locomotion (Gibson, 1958; Lappe et al, 1999; Srinivasan & Zhang, 2004)
The global rate of optical flow refers to the angular motion of features on the retina of an observer and varies with the distance and direction of those features relative to the observer
We developed a dual-task paradigm in which a simple locomotion task was combined with a demanding perceptual discrimination task at a different location from the visual flow

Summary

Introduction

Visual flow is an important perceptual cue that may be used in starting, stopping, and ongoing control of human and non-human locomotion (Gibson, 1958; Lappe et al, 1999; Srinivasan & Zhang, 2004). Visual flow provides information about the speed, direction, and distance of self-motion (Larish & Flach, 1990; Srinivasan et al, 1996; Redlick et al, 2001; Warren et al, 2001; Baird et al, 2005; Durgin et al, 2005), and may be used to calibrate the relation between biomechanical activity and perceived or anticipated speed of self-motion (Rieser et al, 1995; Harris et al, 2000; Proffitt et al, 2003; Durgin et al, 2005). The global rate of optical flow refers to the angular motion of features on the retina of an observer and varies with the distance and direction of those features relative to the observer.

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