Vection Induction Research Articles

Vection induced by low-level motion extracted from complex animation films.

This study examined the contributions of low-, mid- and high-level visual motion information to vection. We compared the vection experiences induced by hand-drawn and computer-generated animation clips to those induced by versions of these movies that contained only their pure optic flow. While the original movies were found to induce longer and stronger vection experiences than the pure optic flow, vection onsets were not significantly altered by removing the mid- and high-level information. We conclude that low-level visual motion information appears to be important for vection induction, whereas mid- and higher-level display information appears to be important for sustaining and strengthening this vection after its initial induction.

The Shepard-Risset Glissando: Identifying the Origins of Metaphorical Auditory Vection and Motion Sickness.

We recently showed that auditory illusions of self-motion can be induced in the absence of physically accurate spatial cues (Mursic et al., 2017). The current study was aimed at identifying which features of this auditory stimulus (the Shepard-Risset glissando) were responsible for this metaphorical auditory vection, as well as confirming anecdotal reports of motion sickness for this stimulus. Five different types of auditory stimuli were presented to 31 blindfolded, stationary participants through a loudspeaker array: (1) a descending Shepard-Risset glissando; (2) a descending discrete Shepard scale; (3) a descending sweep signal; (4) a phase-scrambled version of (1) (auditory control type 1); and (5) white noise (auditory control type 2). We found that the auditory vection induced by the Shepard-Risset glissando was stronger than both types of auditory control, and the discrete Shepard scale stimulus. However, vection strength was not found to differ between the Shepard-Risset glissando and the sweep signal. This suggests that the continuous, gliding structure of both these auditory stimuli was integral to the induction of vection. Consistent with anecdotal reports that the Shepard-Risset glissando is also capable of generating motion sickness (as measured by the Fast Motion Sickness Scale and the Simulator Sickness Questionnaire), the likelihood and severity of sickness for these stimuli was found to increase with the strength of the auditory vection.

Vection strength increases with simulated eye-separation.

Research has previously shown that adding consistent stereoscopic information to self-motion displays can improve the vection in depth induced in physically stationary observers. In some past studies, the simulated eye-separation was always close to the observer's actual eye-separation, as the aim was to examine vection under ecological viewing conditions that provided consistent binocular and monocular self-motion information. The present study investigated whether large discrepancies between the observer's simulated and physical eye-separations would alter the vection-inducing potential of stereoscopic optic flow (either helping, hindering, or preventing the induction of vection). Our self-motion displays simulated eye-separations of 0 cm (the non-stereoscopic control), 3.25 cm (reduced from normal), 6.5 cm (approximately normal), and 13 cm (exaggerated relative to normal). The rated strength of vection in depth was found to increase systematically with the simulated eye-separation. While vection was the strongest in the 13-cm condition (stronger than even the 6.5-cm condition), the 3.25-cm condition still produced superior vection to the 0-cm control (i.e., it had significantly stronger vection ratings and shorter onset latencies). Perceptions of scene depth and object motion-in-depth speed were also found to increase with the simulated eye-separation. As expected based on the findings of previous studies, correlational analyses suggested that the stereoscopic advantage for vection (found for all of our non-zero eye-separation conditions) was due to the increase in perceived motion-in-depth.

Smoothness of stimulus motion can affect vection strength.

We examined the effect of the smoothness of motion on vection strength. The smoothness of stimulus motion was modulated by varying the number of frames comprising the movement. In this study, a horizontal grating translated through 360° of phase in 1s divided into steps of 3, 4, 6, 12, 20, 30, or 60 frames. We hypothesized that smoother motion should induce stronger vection because the smoother stimulus is more natural and contains more motion energy. We examined this effect of frame number on vection for both downward (Experiment 1) and expanding (Experiment 2) optical flow. The results clearly showed that vection strength increased with increasing frame rate, however, the rates of increase in the vection strength with frame rate are not constant, but rapidly increase in the low frame-rate range and appear to asymptote in the high range. The strength estimates saturated at lower frame rates for expanding flow than for downward flow. This might be related to the fact that to process expanding flow it is necessary to integrate motion signals across the visual field. We conclude that the smoothness of the motion stimulus highly affects vection induction.

Roles of Size, Position, and Speed of Stimulus in Vection with Stimuli Projected on a Ground Surface.

Although the induction of vection (perception of illusory self-motion) has been studied for some decades, the effect of ground surface properties on vection remains to be assessed quantitatively. This study will be helpful for designing helicopter or airplane flight simulation, because pilots often perceive optic flow on the ground surface and perceive self-motion from such flows. Vection stimuli of variable position, size, and optic flow speed were presented in a trapezoidal area on a ground surface. Body sway was also measured. Substantial vection was induced by stimuli on a ground surface. Increases in stimulus speed and size were each associated with stronger vection (e.g., the subjective strength increased by 50% as the speed increased from 0.375 m·s(-1) to 1.5 m·s(-1)). When the stimulus occupied a more distant section of the visual field, vection was more efficiently induced than when the nearer section was occupied (e.g., the subjective strength decreased by 50% when the nearer half section of optical flow was removed). These properties of vection were similar to vection induced by upright vertical stimuli. Speed, size, and position of vection stimuli modified both length and direction of body sway significantly. Vection and body sway showed some correlations (e.g., r=0.55). Stimuli on ground surfaces can induce substantial vection and vection strength can be modified by the stimulus properties of the ground surfaces.

Walking without optic flow reduces subsequent vection.

This experiment investigated the effect of walking without optic flow on subsequent vection induction and strength. Two groups of participants walked for 5 min (either wearing Ganzfeld goggles or with normal vision) prior to exposure to a vection-inducing stimulus. We then measured the onset latency and strength of vection induced by a radially expanding pattern of optic flow. The results showed that walking without optic flow transiently yielded later vection onsets and reduced vection strength. We propose that walking without optic flow triggered a sensory readjustment, which reduced the ability of optic flow to induce self-motion perception.

Surface qualities have little effect on vection strength.

We investigated the effects of different surface qualities of materials on vection strength. Previous studies have extensively examined the stimulus parameters for effective vection induction. However, the effects of surface qualities on vection induction have not been studied at all despite their importance in realistic perception of a scene. As a first step toward understanding the effects of surface qualities on vection, we investigated surface qualities derived from light-reflecting properties of nine material categories commonly encountered in daily life: bark, ceramic, fabric, fur, glass, leather, metal, stone and wood. To relate vection strength with low-level visual features and with subjective impression of materials, we analyzed spatial frequency and participants' ratings of adjective pairs that describe impressions of material categories. Although the nine material categories were perceived differently, there was no main effect of material condition on vection strength. However, multiple regression analyses revealed that vection was partially explained by both spatial frequency and principal components extracted from the subjective impression. These results indicate that although the effect of surface qualities of materials on vection is small, both low-level image-based and perceptual-level processing of surface qualities may influence vection1.

Attentional load inhibits vection

In this study, we examined the effects of cognitive task performance on the induction of vection. We hypothesized that, if vection requires attentional resources, performing cognitive tasks requiring attention should inhibit or weaken it. Experiment 1 tested the effects on vection of simultaneously performing a rapid serial visual presentation (RSVP) task. The results revealed that the RSVP task affected the subjective strength of vection. Experiment 2 tested the effects of a multiple-object-tracking (MOT) task on vection. Simultaneous performance of the MOT task decreased the duration and subjective strength of vection. Taken together, these findings suggest that vection induction requires attentional resources.

Inhibition of vection by red

We investigated the effects of colors on vection induction. Expanding optical flows during one's forward self-motion were simulated by moving dots. The dots and the background were painted in equiluminant red and green. Experiments 1 and 2 showed that vection was weaker when the background was red than when the background was green. In addition, Experiment 3 showed that vection was weaker when the moving dots were red than when the dots were green. Experiment 4 demonstrated that red dots on a red background induced very weak vection, as compared with green dots on a green background. In Experiments 5 and 6, we showed that the present results could not be explained by a luminance artifact. Furthermore, Experiment 7 showed that a moving red grating induced weaker vection than did a green one. We concluded that a red visual stimulus inhibits vection.

Vection induction is determined by the world coordinate

Vection induction is determined by the world coordinate

Positional and directional preponderances in vection

We examined the biases in vection strength caused by motion direction (temporonasal vs. nasotemporal motion) and position of stimulus presentation (nasal and temporal semi-retinas) to investigate a subcortical contribution to vection. These biases have been identified for optokinetic nystagmus (OKN) and are acknowledged as evidence for a subcortical origin of OKN. In experiments, subjects monocularly observed hemi-field motion stimuli and made magnitude estimations. The results indicated significant directional and positional biases when luminance modulated gratings were used as stimuli. Vection was stronger with nasotemporal motions and nasal retina presentations, but there were no interactions between the two factors. However, these biases disappeared for second-order motion stimuli (contrast modulation), which are presumably processed by the cortex. In addition, when subjects were asked to make subjective ratings of motion impression, there was no significant difference in subjective strength between the stimuli that induced the strongest vection and weakest vection. These results, together, suggest the involvement of the subcortical pathway in vection induction.

Dominance of ground stimuli in vection induction

Dominance of ground stimuli in vection induction

Galvanic Vestibular Stimulation Modifies Vection Paths in Healthy Subjects

The present study aimed at determining whether vestibular inputs contribute to the perception of the direction of self-motion. This question was approached by investigating the effects of binaural bipolar galvanic vestibular stimulation (GVS) on visually induced self-motion (i.e., vection) in healthy subjects. Stationary seated subjects were submitted to optokinetic stimulation inducing either forward or upward linear vection. While perceiving vection, they were administered trapezoidal GVS of different intensities and ramp durations. Subjects indicated the shape and direction of their perceived self-motion path throughout the experiment by a joystick, and after each trial by the manipulation of a 3D mannequin. Results show that: 1) GVS induced alterations of the path of vection; 2) these alterations occurred more often after GVS onset than after GVS offset; 3) the occurrence of vection path alterations after GVS onset depended on the intensity of GVS but not on the steepness of the GVS variation; 4) the vection path deviated laterally according to either an oblique or a curved path; and 5) the vection path deviated toward the cathode side after GVS onset. It is the first time that vestibular information, already known to contribute to the induction of vection, is shown to modify self-motion perception during the course of vection.