The relative contributions of various viewpoint oscillation frequencies to the perception of distance traveled

Abstract

Humans and most animals are able to navigate in their environment, which generates sensorial information of various kinds, such as proprioceptive cues and optic flow. Previous research focusing on the visual effects of walking (bob, sway, and lunge head motion) has shown that the perception of forward self-motion experienced by static observers can be modulated by adding simulated viewpoint oscillations to the radial flow. In three experimental studies, we examined the effects of several viewpoint oscillation frequencies on static observers' perception of the distance traveled, assuming the assessment of distance traveled to be part of the path integration process. Experiment 1 showed that observers' estimates depended on the frequency of the viewpoint oscillations. In Experiment 2, increasing the viewpoint oscillation frequency actually led to an increase in the global retinal flow. It also emerged that simulated viewpoint oscillations enhance the sensation of self-motion: In a specific low-frequency range (<4 Hz), they improved subjects' estimates of the distances traveled. Lastly, in Experiment 3, observers were presented with two different simulated viewpoint oscillation patterns, both involving the same amount of global retinal motion, but in one case, the pattern simulated the visual effects of natural walking, and in the other case, the pattern was not biologically realistic. Contrary to the predictions of a previous ecological hypothesis, the subjects gave similar responses under both conditions. The global retinal motion may be mainly responsible for these effects, which were found to be optimal in a specific fairly low-oscillation frequency range.

Viewpoint oscillation improves the perception of distance travelled in static observers but not during treadmill walking

“…In the first experiment, static observers had to carry out a distance travelled estimation task while facing either a purely linear visual simulation of self-motion (in depth) or one to which viewpoint oscillations directly based on their own head oscillations previously recorded during treadmill walking were added. Results confirm that the benefits of viewpoint oscillation are maintained in an HMD, as established as in our previous studies conducted in a CAVE system (Bossard et al 2016;Bossard and Mestre 2018). The second experiment was designed to test whether the absence of viewpoint oscillations during treadmill walking (when visual consequences of the head translations generated by walking are deleted; non-oscillatory condition) affects subjects' perception of self-motion in comparison with a more complete pattern of visual feedback other dynamic cues.…”

“…Based on the use of an HMD, Experiment 1 showed the reproducibility of the results obtained in our previous studies (Bossard et al 2016;Bossard and Mestre 2018) conducted in a CAVE system as regards the benefits to distance travelled perception of viewpoint oscillations in comparison with a purely linear simulation of self-motion. At this point, it was proposed to address the question as to whether the benefits of viewpoint oscillations are maintained during multisensory perception of self-motion or more specifically, whether or not the perception of distance travelled is affected when the visual consequences of head movements are removed from the visual simulation of forward self-motion during treadmill walking.…”

“…They tended to respond too early during the first few blocks, and their assessments tended to stabilize during the subsequent trials. As in our previous studies (Bossard et al 2016;Bossard and Mestre 2018), further analyses were conducted on the last 4 blocks alone, to determine at what point the Block factor effect disappeared (F (3, 51) = 0.87, p > 0.05; see Fig. 2a).…”

“…On the tunnel floor, the subject could see a target, a "roadworks" beacon of the usual size (height: 70 cm). This target was placed at initial virtual distances of 6, 12, 18, 24 or 30 m relative to the observer, depending on the trial (Bossard et al 2016;Bossard and Mestre 2018;Plumert et al 2005).…”

“…The main conclusion reached on the basis of these experiments was that this effect may be due to an increase in the global retinal motion. However, the possible contribution of an "ecological" factor cannot be ruled out: a second series of experiments (Bossard and Mestre 2018) in which the viewpoint oscillation frequency was made to vary showed that the optimal performances were recorded in a similar range of frequencies to those of the head motion which occurs during natural walking.…”