Influence of Visual Motion, Suggestion, and Illusory Motion on Self-Motion Perception in the Horizontal Plane.

Benjamin Thomas Crane,Marko Nardini,Steven David Rosenblatt

doi:10.1371/journal.pone.0142109

Abstract

A moving visual field can induce the feeling of self-motion or vection. Illusory motion from static repeated asymmetric patterns creates a compelling visual motion stimulus, but it is unclear if such illusory motion can induce a feeling of self-motion or alter self-motion perception. In these experiments, human subjects reported the perceived direction of self-motion for sway translation and yaw rotation at the end of a period of viewing set visual stimuli coordinated with varying inertial stimuli. This tested the hypothesis that illusory visual motion would influence self-motion perception in the horizontal plane. Trials were arranged into 5 blocks based on stimulus type: moving star field with yaw rotation, moving star field with sway translation, illusory motion with yaw, illusory motion with sway, and static arrows with sway. Static arrows were used to evaluate the effect of cognitive suggestion on self-motion perception. Each trial had a control condition; the illusory motion controls were altered versions of the experimental image, which removed the illusory motion effect. For the moving visual stimulus, controls were carried out in a dark room. With the arrow visual stimulus, controls were a gray screen. In blocks containing a visual stimulus there was an 8s viewing interval with the inertial stimulus occurring over the final 1s. This allowed measurement of the visual illusion perception using objective methods. When no visual stimulus was present, only the 1s motion stimulus was presented. Eight women and five men (mean age 37) participated. To assess for a shift in self-motion perception, the effect of each visual stimulus on the self-motion stimulus (cm/s) at which subjects were equally likely to report motion in either direction was measured. Significant effects were seen for moving star fields for both translation (p = 0.001) and rotation (p<0.001), and arrows (p = 0.02). For the visual motion stimuli, inertial motion perception was shifted in the direction consistent with the visual stimulus. Arrows had a small effect on self-motion perception driven by a minority of subjects. There was no significant effect of illusory motion on self-motion perception for either translation or rotation (p>0.1 for both). Thus, although a true moving visual field can induce self-motion, results of this study show that illusory motion does not.

Highlights

Visual field motion can ambiguously be perceived as either self-motion in a fixed environment or as external motion relative to a fixed observer
There is some consensus that the illusory motion effect results from timing differences between neuronal responses to different contrast and/or luminance elements, and that static repeated asymmetric patterns (RAPs) evoke a similar pattern of neural activity that occurs when objects are moving [10, 11]
For the illusory motion visual stimulus, we used a static repeated asymmetric pattern mapped onto a torus (Fig 1, top) that was rendered by Beau Dealy

Summary

Introduction

Visual field motion can ambiguously be perceived as either self-motion in a fixed environment or as external motion relative to a fixed observer. Like many studies of vection[17,18,19,20,21], the Seno et al study used a magnitude estimation technique,[22] which involved having observers give a subjective numeric value to their perception. Such subjective reporting makes it difficult to determine if differences in subject responses are due to the underlying perception or to the interpretation of the stimulus in relation to the reporting scale [23,24,25]. Because magnitude estimation techniques are often not standardized between studies, it makes it difficult to make comparisons

Methods

Results

Conclusion