Evidence against an ecological explanation of the jitter advantage for vection

Abstract

Visual-vestibular conflicts have been traditionally used to explain both perceptions of self-motion and experiences of motion sickness. However, sensory conflict theories have been challenged by findings that adding simulated viewpoint jitter to inducing displays enhances (rather than reduces or destroys) visual illusions of self-motion experienced by stationary observers. One possible explanation of this jitter advantage for vection is that jittering optic flows are more ecological than smooth displays. Despite the intuitive appeal of this idea, it has proven difficult to test. Here we compared subjective experiences generated by jittering and smooth radial flows when observers were exposed to either visual-only or multisensory self-motion stimulations. The display jitter (if present) was generated in real-time by updating the virtual computer-graphics camera position to match the observer’s tracked head motions when treadmill walking or walking in place, or was a playback of these head motions when standing still. As expected, the (more naturalistic) treadmill walking and the (less naturalistic) walking in place were found to generate very different physical head jitters. However, contrary to the ecological account of the phenomenon, playbacks of treadmill walking and walking in place display jitter both enhanced visually induced illusions of self-motion to a similar degree (compared to smooth displays).

Viewpoint oscillation improves the perception of distance travelled based on optic flow

“…The latter authors' original explanation for this effect, in line with our initial hypothesis, was that oscillations added to a linear flow may increase the sensation of vection because it triggers visual self-motion processing and is therefore more ''ecological.'' However, recent studies have challenged this rather simple hypothesis (Palmisano, Allison, Ash, Nakamura, & Apthorp, 2014) by showing that the ecological aspect of added oscillations did not affect the contribution of jitter to vection. Two alternative explanations have been put forward for these effects at a more basic motion perception level.…”

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

“…In line with the retinal motion hypothesis (Hypothesis 2), which suggests that an increase in the global retinal motion might strengthen the sensation of self-motion, the results of Experiments 1 and 2 show that the participants tended to estimate the distance traveled more accurately when they were exposed to LF and MF conditions than to the Linear condition, whereas when more retinal motion occurred in the HF condition, participants give less accurate distance traveled estimates. At this point, the third experiment was designed to test whether the benefits of simulated viewpoint oscillation might be restricted to a range of frequencies inducing in the participants similar visual effects to those of head movements triggered during walking, which might tap into the visual processes normally involved in the perception of self-motion (Bubka & Bonato, 2010;Lécuyer et al, 2006;Palmisano et al, 2014;Hypothesis 4). In Experiment 3, the two conditions of simulated viewpoint oscillation induced the same amount of visual motion (and hence the same amount of global retinal motion), but one of them was based on a pattern resembling the visual effects of natural walking (the bio-coherent condition) and the other on a biologically unrealistic pattern (the bioincoherent condition).…”

“…These visual oscillations are therefore naturally linked to the proprioceptive and vestibular information generated when we are walking, and they may therefore contribute importantly to the perception of our own movements. The authors of a few studies (Durgin, Gigone, & Scott, 2005;Kim, Chung, Nakamura, Palmisano, & Khuu, 2015;Kim & Khuu, 2014;Kim & Palmisano, 2008;Kim, Palmisano, & Bonato, 2012;Palmisano, Allison, Ash, Nakamura, & Apthorp, 2014;Palmisano et al, 2000) have examined how the visual effects of the head motion that occurs during walking contribute to selfmotion perception. Kim and his colleagues have shown that adding simulated head oscillations to a radial optic flow can increase the strength of the in-depth illusion of self-motion (i.e., linear vection), but the process underlying this enhancement still remains to be explained.…”

Perceiving jittering self-motion in a field of lollipops from ages 4 to 95

“…In other words, we found a similar enhancement from jittering flow regardless of age. This null finding is hard to interpret but could indicate that the jitter effect is not tuned to the fine details of ecological jitter as others have argued [ 38 ] or that any developmental effect is small relative to inter-subject variability.…”

“…Adding viewpoint jitter to visually simulated self-motion also improves the perception of distance travelled [ 36 , 37 ]. The underlying reason that jittering flow increases percepts of self-motion is currently unclear [ 35 , 38 , 39 ]. Palmisano et al [ 35 ] outlined several possible explanations including that jitter might improve the perception of 3D layout or scene rigidity, reduce motion adaptation, increase retinal slip, indirectly suppress (or stimulate) vestibular cortical areas, or provide a more ecological stimulus better matched to self-motion processing.…”