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Biomedical subjects

T A Stoffregen

Publications and source records attributed to T A Stoffregen.

15 recordsLinked to original sources
PubMed2001

On specification and the senses.

In this target article we question the assumption that perception is divided into separate domains of vision, hearing, touch, taste, and smell. We review implications of this assumption for theories of perception and for our understanding of ambient energy arrays (e.g., the optic and acoustic arrays) that are available to perceptual systems. We analyze three hypotheses about relations between ambient arrays and physical reality: (1) that there is an ambiguous relation between ambient energy arrays and physical reality, (2) that there is a unique relation between individual energy arrays and physical reality, and (3) that there is a redundant but unambiguous relation, within or across arrays, between energy arrays and physical reality. This is followed by a review of the physics of motion, focusing on the existence and status of referents for physical motion. Our review indicates that it is not possible, in principle, for there to be a unique relation between physical motion and the structure of individual energy arrays. We argue that physical motion relative to different referents is specified only in the global array, which consists of higher-order relations across different forms of energy. The existence of specificity in the global array is consistent with the idea of direct perception, and so poses a challenge to traditional, inference-based theories of perception and cognition. However, it also presents a challenge to much of the ecological approach to perception and action, which has accepted the assumption of separate senses.

Auditory Perception↗
PubMed2000

Postural instability and motion sickness in a fixed-based flight simulator.

We evaluated the prediction that postural instability would precede the subjective symptoms of motion sickness in a fixed-base flight simulator. Participants sat in a cockpit in a video projection dome and were exposed to optical flow that oscillated in the roll axis with exposure durations typical of flight simulation. The frequencies of oscillation were those that characterize spontaneous postural sway during stance. Head motion was measured prior to and during exposure to imposed optical flow. Of 14 participants, 6 were classified as motion sick, either during or after exposure to the optical oscillation. Prior to the onset of subjective symptoms, head motion among participants who later became sick was significantly greater than among participants who did not become motion sick. We argue that the results support the postural instability theory of motion sickness. Actual or potential applications include the prevention or mitigation of motion sickness in virtual environments.

Adult↗
PubMed1999

Perceiving affordances for another person's actions.

The perception of affordances for the actions of other people (actors) was examined. Observers judged the maximum and preferred sitting heights of tall and short actors. Judgments were scaled in centimeters, as a proportion of the observer's leg length, and as a proportion of each actor's leg length. In Experiment 1 observers viewed live actors standing next to a chair. When judgments were scaled by actor leg length, they reflected the actual ordinal relation between the capabilities of the actors. The perception of affordances from kinematic displays was then evaluated. Observers differentiated tall and short actors, but only when the displays contained direct information about relations between the actors and the chair. It is concluded that observers can perceive affordances for the actions of actors and that kinematic displays can be enough to support such percepts if they preserve actor-environment relations that define affordances.

Adult↗
PubMed1999

Postural coordination modes considered as emergent phenomena.

The coordination of multiple body segments (torso and legs) in the control of standing posture during a suprapostural task was studied. The analysis was motivated by dynamical theories of motor coordination. In 2 experiments it was found that multisegment postural coordination could be described by the relative phase of rotations around the hip and ankle joints. The effective length of the feet, the height of the center of mass, and the amplitude of head motions in a visual tracking task were varied. Across these variations, 2 modes of hip-ankle coordination were observed: in-phase and anti-phase. The emergence of these modes was influenced by constraints imposed by the suprapostural tracking task, supporting the idea that such tasks influence postural control in an adaptive manner. Results are interpreted in terms of a dynamical approach to coordination in which postural coordination modes can be viewed as emergent phenomena.

Adult↗
PubMed1998

Postural instability precedes motion sickness.

We evaluated the hypothesis that postural instability precedes the onset of motion sickness. Subjects standing in a "moving room" were exposed to nearly global oscillating optical flow. In the experimental condition, the optical oscillations were a complex sum-of-sines between 0.1 and 0.3 Hz, with an excursion of 1.8 cm. This optical motion was of such low frequency and magnitude that it was sometimes not noticed by subjects. However, in two experiments, exposure to the moving room produced significant increases in scores on a standard motion sickness questionnaire. In addition, approximately half of subjects reported motion sickness. Analysis of postural motion during exposure to the moving room revealed increases in postural sway before the onset of subjective motion sickness symptoms. This confirms a key prediction of the postural instability theory of motion sickness.

Adaptation, Physiological↗
PubMed1998

Self-induced motion sickness in unperturbed stance.

Motion sickness typically occurs when the body is subjected to externally imposed motions, but there are situations in which sickness occurs in the absence of imposed motion. We report a new and unanticipated instance of the latter. Subjects in a study of spontaneous standing postural sway sometimes reported dizziness and motion sickness. Reports of sickness were correlated with changes in postural sway. We consider possible implications of these findings for two current theories of motion sickness etiology: the sensory conflict theory and the postural instability theory.

Adaptation, Physiological↗
PubMed1993

Noticing of unexpected events by adults with and without mental retardation.

Adults without mental retardation commonly fail to notice nominally obvious aspects of naturalistic scenes (Becklen & Cervone, 1983). We replicated and extended this effect to adults with mild mental retardation. Adults with and without retardation viewed a 60-second videotape of an amateur basketball game. They were instructed to press a button whenever the ball was passed. At one point, a woman carrying an open umbrella walked bodily through the ongoing action. Becklen and Cervone found that only 35% of adults without retardation noticed this unexpected event and that noticing was not predicted by task performance prior to the woman's appearance. In the present study noticing rates for subjects without retardation were similar to those reported by Becklen and Cervone and noticing by subjects with mental retardation was at least as high. Task performance for subjects with mental retardation was significantly lower than that of subjects without retardation, but noticing was not predicted by task performance (prior to the unexpected event) for either group. Results were interpreted in the context of an ecological approach to attention.

Adolescent↗
PubMed1992

The role of balance dynamics in the active perception of orientation.

The Stoffregen and Riccio (1988) hypothesis that perceived orientation is determined primarily by balance dynamics was tested. Perception of orientation was evaluated in the context of a task that required Ss to control the roll orientation of a device in which they were seated. The device's direction of balance was manipulated across trials and thus was independent of gravity. Eighteen Ss participated in the investigation. After each trial, Ss estimated their mean tilt with respect to upright. Correlations of perceived tilt with tilt from balance were consistently higher than the correlations with gravity tilt. The dominance of balance over gravity depended on the magnitude of tilt from balance.

Adult↗
PubMed1990

Gravitoinertial force versus the direction of balance in the perception and control of orientation.

Curthoys and Wade (1990) appeal to land-based data in defending the traditional view that stimulation of the otolith organs leads to perception of the direction of gravitoinertial force. However, such data do not permit rejection of the hypothesis that the perception of orientation is based on the dynamically defined direction of balance, which is qualitatively different from the kinetically defined direction of gravitoinertial force. Furthermore, the approach of Curthoys and Wade is compromised by their failure to consider relations between the perception and control of orientation. Such relations must be considered in developing a general theory of orientation.

Gravitation↗
PubMed1989

Dual attention to dynamically structured naturalistic events.

Videotapes of two naturalistic events, a basketball-like game and a vocalizing human face, were presented in a dual-task situation, with subjects responding to target events in individual episodes. The fact that the stimulus episodes consisted of natural motions permitted subjects to base their attention on the partially determinate structure that characterizes such motions. Simultaneous visual presentations were in full transparent overlap. the auditory presentations were overlapped spatially. Performance on the dual task improved significantly in all experimental conditions over two days of practice. Performance approached control-group ceiling levels for events available to different modalities (hearing and sight). When information was available only in a single modality, performance was lower over-all, but practice effects were still significant. The results are discussed in the context of a cognitive skills approach to attention.

Adult↗
PubMed1987

Detection of the traversability of surfaces by crawling and walking infants.

In four studies we investigated the perception of the affordance for traversal of a supporting surface. The surface presented was either rigid or deformable, and this property was specified either optically, haptically, or both. In Experiment 1A, crawling and walking infants were presented with two surfaces in succession: a standard surface that both looked and felt rigid and a deforming surface that both looked and felt nonrigid. Latency to initiate locomotion, duration of visual and haptic exploration, and displacement activity were coded from videotapes. Compared with the standard, the deforming surface elicited longer latency, more exploratory behavior, and more displacement in walkers, but not in crawlers, suggesting that typical mode of locomotion influences perceived traversability. These findings were replicated in Experiment 1B, in which the infant was presented with a dual walkway, forcing a choice between the two surfaces. Experiments 2, 3A and B, and 4A and B investigated the use of optical and haptic information in detecting traversability of rigid and nonrigid surfaces. Patterns of exploration varied with the information presented and differed for crawlers and walkers in the case of a deformable surface, as an affordance theory would predict.

Attention↗
PubMed1987

Use of central and peripheral optical flow in stance and locomotion in young walkers.

Young walkers (up to 5 years of age) were presented with optical flow in a moving room. Flow was global or was restricted to either the center or the periphery of the visible optic array. On standing trials the response rate was greatest when peripheral flow was available. The availability of central flow had a smaller effect on standing, and the younger children showed greater response rates to frontal flow than did the older ones. There was a strong negative correlation between age and response rate for all conditions. Flow also affected stability during locomotion. Response rate was again related to the location of the available flow. It is concluded that children show the same relative sensitivity for flow in the periphery of the dynamic structure of the optic array as has been observed in adults, but that this differentiation of different areas of optical structure is not yet fully developed when children learn to stand.

Age Factors↗
PubMed1985

Flow structure versus retinal location in the optical control of stance.

In four experiments I examined the importance of the retinal center and periphery in the pickup of optical information for controlling stance as a function of the dynamic geometrical structure of the optical flow. All experiments were performed in a moving room so that the magnitude of compensatory sway in response to room movements could be measured. In Experiments 1 and 2 I found stronger sway response to flow having a largely lamellar structure that was presented to the retinal periphery than to more radially structured flow in the center. In Experiment 3 observers turned their heads to face the right wall of the room, placing radial flow in the periphery and lamellar flow in the center of the visual field. Radial flow presented to the retinal periphery induced no compensatory sway. Lamellar flow in the center of the retina produced some sway. Flow structure apparently interacts with the exposed retinal area in controlling stance.

Biophysical Phenomena↗