Spatiotemporal influences on the recognition of two-dimensional vibrotactile patterns on the abdomen.

Spatial and temporal factors are known to highly influence tactile perception, but their role has been largely unexplored in the case of two-dimensional (2D) pattern recognition. We investigated whether recognition is facilitated by the spatial and/or temporal separation of pattern elements, or by conditions known to favor perceptual integration, such as the ones eliciting apparent movement. 2D vibrotactile patterns were presented to the abdomen of novice participants. In Experiment 1, we manipulated the spatial (inter-tactor distance) and temporal (burst duration and inter-burst interval) parameters applied to the tracing mode (sequential activation of pattern elements). In Experiment 2, we compared display modes differing in their level of temporal overlap in the presentation of pattern elements: the static mode (simultaneous activation of pattern elements), the slit-scan mode (pattern revealed line by line), and the tracing mode. The results of both experiments reveal that (a) recognition performance increases with the isolation of pattern elements in space and/or in time, (b) spatial and temporal factors interact in pattern recognition, and (c) conditions leading to apparent movement tend to be associated with lower recognition accuracy. These results further our understanding of tactile perception and provide guidance for the design of future vibrotactile communication systems. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Head Stability and Head-Trunk Coordination in Horseback Riders: The Contribution of Visual Information According to Expertise.

Maintaining equilibrium while riding a horse is a challenging task that involves complex sensorimotor processes. We evaluated the relative contribution of visual information (static or dynamic) to horseback riders' postural stability (measured from the variability of segment position in space) and the coordination modes they adopted to regulate balance according to their level of expertise. Riders' perceptual typologies and their possible relation to postural stability were also assessed. Our main assumption was that the contribution of visual information to postural control would be reduced among expert riders in favor of vestibular and somesthetic reliance. Twelve Professional riders and 13 Club riders rode an equestrian simulator at a gallop under four visual conditions: (1) with the projection of a simulated scene reproducing what a rider sees in the real context of a ride in an outdoor arena, (2) under stroboscopic illumination, preventing access to dynamic visual cues, (3) in normal lighting but without the projected scene (i.e., without the visual consequences of displacement) and (4) with no visual cues. The variability of the position of the head, upper trunk and lower trunk was measured along the anteroposterior (AP), mediolateral (ML), and vertical (V) axes. We computed discrete relative phase to assess the coordination between pairs of segments in the anteroposterior axis. Visual field dependence-independence was evaluated using the Rod and Frame Test (RFT). The results showed that the Professional riders exhibited greater overall postural stability than the Club riders, revealed mainly in the AP axis. In particular, head variability was lower in the Professional riders than in the Club riders in visually altered conditions, suggesting a greater ability to use vestibular and somesthetic information according to task constraints with expertise. In accordance with this result, RFT perceptual scores revealed that the Professional riders were less dependent on the visual field than were the Club riders. Finally, the Professional riders exhibited specific coordination modes that, unlike the Club riders, departed from pure in-phase and anti-phase patterns and depended on visual conditions. The present findings provide evidence of major differences in the sensorimotor processes contributing to postural control with expertise in horseback riding.

Evaluation of heading performance with vibrotactile guidance: the benefits of information-movement coupling compared with spatial language.

This study quantified the effectiveness of tactile guidance in indicating a direction to turn to and measured its benefits compared to spatial language. The device (CAYLAR), which was composed of 8 vibrators, specified the requested direction by a vibration at the corresponding location around the waist. Twelve participants were tested in normal light and in total darkness with 3 guidance conditions: spatial language, a long tactile rhythm (1 s on/4 s off vibrations) providing a single stimulation before movement, and a short rhythm (200 ms on/200 ms off vibrations) allowing information-movement coupling during body rotation. We measured response time, heading error, and asked participants to rate task easiness, intuitiveness and perceived accuracy for each guidance mode. Accuracy was higher and participants' ratings were more positive with the short tactile mode than with the 2 other modes. Compared to spatial language, tactile guidance, regardless of the vibration rhythm, also allowed faster responses and did not impair accuracy in the absence of vision. These findings quantitatively demonstrate that tactile guidance is particularly effective when it is reciprocally related to movement. We discuss implications of the benefits of perception-action coupling for the design of tactile navigation devices.

(De)stabilization of required and spontaneous postural dynamics with learning.

The present research examined how learning a new ankle-hip coordination influenced the preexisting postural repertoire. Standing participants learned a new ankle-hip coordination mode (relative phase of 90'). Before and after practice, postural patterns were evaluated in two different tasks. In the required task, specific ankle-hip patterns were requested (12 relative phases in multiples of 30'). In the spontaneous task, participants performed a tracking task in which no instructions about ankle-hip coordination were given. Learning induced changes in both required and spontaneous coordination dynamics. When ankle-hip patterns were required, learning led to improvement and homogenization in performance over the entire postural repertoire. When ankle-hip patterns emerged spontaneously, in-phase and antiphase preexisting patterns destabilized and changed toward the learned pattern of 90'. These findings demonstrate that learning a new coordination pattern can induce modifications of patterns that have not been practiced. The results also suggest that the consequences of learning do not generalize across different types of tasks, even when similar coordination modes are involved. We discuss implications of these findings for the generality of learning mechanisms.

Motion sickness and postural sway in console video games.

OBJECTIVE: We tested the hypotheses that (a) participants might develop motion sickness while playing "off-the-shelf" console video games and (b) postural motion would differ between sick and well participants, prior to the onset of motion sickness. BACKGROUND: There have been many anecdotal reports of motion sickness among people who play console video games (e.g., Xbox, PlayStation). METHOD: Participants (40 undergraduate students) played a game continuously for up to 50 min while standing or sitting. We varied the distance to the display screen (and, consequently, the visual angle of the display). RESULTS: Across conditions, the incidence of motion sickness ranged from 42% to 56%; incidence did not differ across conditions. During game play, head and torso motion differed between sick and well participants prior to the onset of subjective symptoms of motion sickness. CONCLUSION: The results indicate that console video games carry a significant risk of motion sickness. APPLICATION: Potential applications of this research include changes in the design of console video games and recommendations for how such systems should be used.

Motion sickness, console video games, and head-mounted displays.

OBJECTIVE: We evaluated the nauseogenic properties of commercial console video games (i.e., games that are sold to the public) when presented through a head-mounted display. BACKGROUND: Anecdotal reports suggest that motion sickness may occur among players of contemporary commercial console video games. METHODS: Participants played standard console video games using an Xbox game system. We varied the participants' posture (standing vs. sitting) and the game (two Xbox games). Participants played for up to 50 min and were asked to discontinue if they experienced any symptoms of motion sickness. RESULTS: Sickness occurred in all conditions, but it was more common during standing. During seated play there were significant differences in head motion between sick and well participants before the onset of motion sickness. CONCLUSION: The results indicate that commercial console video game systems can induce motion sickness when presented via a head-mounted display and support the hypothesis that motion sickness is preceded by instability in the control of seated posture. APPLICATION: Potential applications of this research include changes in the design of console video games and recommendations for how such systems should be used.

Motion sickness, body movement, and claustrophobia during passive restraint.

Standing participants were passively restrained and exposed to oscillating visual motion. Thirty-nine percent of participants reported motion sickness. Despite passive restraint, participants exhibited displacements of the center of pressure, and prior to the onset of motion sickness the evolution of these displacements differed between participants who later became sick and those who did not. Claustrophobia occurred during restraint, but only among participants who became motion sick. The results are consistent with the postural instability theory of motion sickness. We discuss the possible relation between claustrophobia symptoms, postural movements and motion sickness incidence.

Dynamics of learning new postural patterns: influence on preexisting spontaneous behaviors.

In stance, rotations around the hips and ankles typically exhibit a relative phase close to 20 degrees or 180 degrees . In 2 experiments, the authors studied the reciprocal influence of those coordination tendencies with learning an ankle-hip relative phase of 135 degrees . Before, during, and after learning a new mode of coordination, they assessed participants' (N = 24 in each experiment) spontaneous postural patterns with a tracking task in which no specific coordination was required. Learning the 135 degrees phase relation led to persistent modifications of the spontaneous in-phase and antiphase modes. Contrary to the theoretical predictions of the dynamical approach, the initial stability of the preexisting patterns did not influence the difficulty of producing the new mode or the improvement in performance during learning. Initial stability did, however, influence the rate and type of modification of spontaneous patterns. The authors discuss the results in relation to conclusions drawn from bimanual studies.

Motion sickness preceded by unstable displacements of the center of pressure.

We exposed standing participants to optic flow in a moving room. Motion sickness was induced by motion that simulated the amplitude and frequency of standing sway. We identified instabilities in displacements of the center of pressure among participants who became sick; these instabilities occurred before the onset of subjective motion sickness symptoms. Postural differences between Sick and Well participants were observed before exposure to the nauseogenic stimulus. During exposure to the nauseogenic stimulus, sway increased for participants who became sick but also for those who did not. However, at every point during exposure sway was greater for participants who became motion sick. The results reveal that motion sickness is preceded by instabilities in displacements of the center of pressure.

Exploring coordination dynamics of the postural system with real-time visual feedback.

Differential performance over a wide range of possible postural coordination modes was investigated using 16 ankle-hip relative phase patterns from 0 degrees to 337.5 degrees. Participants were instructed to produce each coordination mode with and without real time visual feedback. Feedback consisted of a Lissajous figure indicating the discrepancy between actual and requested ankle-hip relative phase. The results showed: (1) the presence of a unique attractor around the anti-phase pattern (relative phase approximately 180 degrees); (2) performance was similar with and without visual feedback; (3) the absence of an attractor for the in-phase pattern (relative phase approximately 20 degrees). The third result is not consistent with previous research in which both in-phase and anti-phase patterns emerged when they were not imposed [B.G. Bardy, L. Martin, T.A. Stoffregen, R.J. Bootsma, Postural coordination modes considered as emergent phenomena, J. Exp. Psychol. Hum. Percept. Perform. 25 (1999) 1284-1301; B.G. Bardy, O. Oullier, R.J. Bootsma, T.A. Stoffregen, Dynamics of human postural transitions, J. Exp. Psychol. Hum. Percept. Perform. 28 (1999) 499-514]. This finding indicates the strong dependency to task variation and instructions of postural pattern formation.