An ecological Theory of Motion Sickness and Postural Instability

In this article we present a new theory of motion sickness. In the sensory conflict theory, changes in stimulation of perceptual systems are believed to be responsible for motion sickness. We discuss the fact that these changes in stimulation are not independent of the animal-environment interaction, but are determined by corresponding changes in the constraints operating on the control of action. Thus, provocative situations may be characterized by novel demands on the control of action as well as by novel patterns of stimulation. Our hypothesis is that animals become sick in situations in which they do not possess (or have not yet learned) strategies that are effective for the maintenance of postural stability. We identify a broad range of situations over which the occurrence of motion sickness is related to factors that should influence postural stability. This allows us to establish a logical link between motion sickness and postural stability. Our analysis implies that an understanding of stability should be an important part of the agenda in research on perception and action in general. We suggest that postural instability could be related to the concept of dynamical disease which has been developed in the literature on nonlinear physiological control systems. We conclude with suggestions for research based on the new approach.     

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.     

An Experimental Evaluation of Sensory Conflict Versus Postural Control Theories of Motion Sickness

Riccio and Stoffregen (1991) presented a radical alternative to the widely accepted sensory conflict theory of motion sickness. Essentially, they argued that motion sickness is caused not by sensory conflict, but by postural instability. The current experiment was designed to evaluate three aspects of the two theories. Participants were exposed to two levels of sensory conflict while being partially restrained to reduce the possibility of postural instability. The results were that (1) motion sickness was widespread although there were few signs of postural instability, (2) difference in motion sickness were associated with differences in sensory conflict rather than with differences in postural stability, and (3) the frequency range of movements that preceded symptoms of motion sickness was not in the 4 to 8 Hz band, contrary to the prediction of Riccio and Stoffregen. Although these results must be treated with caution due to the limits of the resolving power of the analysis of participants' movements, we conclude that although the postural instability explanation has more ecological validity, it is not correct in its current form and deserves further empirical investigation.     

The sickening rug: a repeating static pattern that leads to motion-sickness-like symptoms

The nauseogenic properties of a patterned rug that reputedly caused motion-sickness-like symptoms in those who viewed it was the topic of this study. Naive observers viewed a 1:1 scale image of the black-and-white patterned rug and a homogeneous gray region of equivalent luminance in a counterbalanced within-subjects design. After 5 min of viewing, symptoms were assessed with the simulator sickness questionnaire (SSQ), yielding a total SSQ score and sub-scores for nausea, oculomotor symptoms, and disorientation. All four scores were significantly higher in the rug condition. Observers also reported significantly more self-motion perception in the rug condition, even though they were seated during the experiment. Results are consistent with findings that suggest that neurologically normal individuals who view a repeating static pattern can experience unpleasant symptoms, some of which are similar to motion sickness.     

Expanding and contracting optic-flow patterns and vection

When stationary observers view an optic-flow pattern, visually induced self-motion perception (vection) and a form of motion sickness known as simulator sickness (SS), can result. Previous results suggest that an expanding flow pattern leads to more SS than a contracting pattern. Sensory conflict, a possible cause of SS, may be more salient when an expanding optic-flow pattern is viewed. An experiment was conducted to test if a more salient sensory conflict accompanying expanding flow patterns might inhibit vection. Participants (n = 15) viewed a pattern of blue squares, either steadily expanded or contracted, on a large rear-projection screen. Vection onset and magnitude were measured for 30 s with a computer-interfaced slide device. Vection onset was significantly faster, and vection magnitude stronger, when a contracting pattern was viewed. We propose that our extensive experience with forward self-motion may form a neural expectancy (exposure-history) about the sensory inputs which typically accompany expanding flow. However, since backward self-motion is less common, there may be a weaker exposure-history for contracting flow, and as a result these patterns generate less salient sensory conflict and subsequently less vection.     

Effect of a novel motion desensitization training regime and controlled breathing on habituation to motion sickness

To study whether controlled breathing, known to ameliorate motion sickness, speeds habituation to nauseogenic motion when used in a novel accelerated training regime, 30 participants (13 men, 17 women, ages 18-51 years) were randomized to either a Breathing group or a Control group. Randomization was balanced for rotation tolerance measured during a first exposure to off-vertical axis rotation (OVAR 72 degrees sec.(-1)). Participants subsequently received four exposures to OVAR in 1-hr. (accelerated training). The Breathing group followed taped instructions to control their breathing during training and when retested the next day. There was overall habituation with stimulus repetition, shown by an increase in tolerance for motion, a reduction in symptoms, and speeded recovery times on retesting. There was a tendency for greater habituation with controlled breathing.     

Control of a virtual vehicle influences postural activity and motion sickness

Everyday experience suggests that drivers are less susceptible to motion sickness than passengers. In the context of inertial motion (i.e., physical displacement), this effect has been confirmed in laboratory research using whole body motion devices. We asked whether a similar effect would occur in the context of simulated vehicles in a visual virtual environment. We used a yoked control design in which one member of each pair of participants played a driving video game (i.e., drove a virtual automobile). A recording of that performance was viewed (in a separate session) by the other member of the pair. Thus, the two members of each pair were exposed to identical visual motion stimuli, but the risk of behavioral contagion was minimized. Participants who drove the virtual vehicle (drivers) were less likely to report motion sickness than participants who viewed game recordings (passengers). Data on head and torso movement revealed that drivers tended to move more than passengers, and that the movements of drivers were more predictable than the movements of passengers. Before the onset of subjective symptoms of motion sickness movement differed between participants who (later) reported motion sickness and those who did not, consistent with a prediction of the postural instability theory of motion sickness. The results confirm that control is an important factor in the etiology of motion sickness and extend this finding to the control of noninertial virtual vehicles.     

Comparing simulator sickness in younger and older adults during simulated driving under different multisensory conditions

Driving simulators are valuable tools for traffic safety research as they allow for systematic reproductions of challenging situations that cannot be easily tested during real-world driving. Unfortunately, simulator sickness (i.e., nausea, dizziness, etc.) is common in many driving simulators and may limit their utility. The experience of simulator sickness is thought to be related to the sensory feedback provided to the user and is also thought to be greater in older compared to younger users. Therefore, the present study investigated whether adding auditory and/or motion cues to visual inputs in a driving simulator affected simulator sickness in younger and older adults. Fifty-eight healthy younger adults (age 18–39) and 63 healthy older adults (age 65+) performed a series of simulated drives under one of four sensory conditions: (1) visual cues alone, (2) combined visual + auditory cues (engine, tire, wind sounds), (3) combined visual + motion cues (via hydraulic hexapod motion platform), or (4) a combination of all three sensory cues (visual, auditory, motion). Simulator sickness was continuously recorded while driving and up to 15 min after driving session termination. Results indicated that older adults experienced more simulator sickness than younger adults overall and that females were more likely to drop out and drove for less time compared to males. No differences between sensory conditions were observed. However, older adults needed significantly longer time to fully recover from the driving session than younger adults, particularly in the visual-only condition. Participants reported that driving in the simulator was least realistic in the visual-only condition compared to the other conditions. Our results indicate that adding auditory and/or motion cues to the visual stimulus does not guarantee a reduction of simulator sickness per se, but might accelerate the recovery process, particularly in older adults.     

From Blind to Creative: In Defense of Donald Campbell's Selectionist Theory of Human Creativity

Both Perkins and Sternberg recognize Campbell's selectionist theory of knowledge generation as accounting for certain types of learning and human creativity. However, they argue that his theory cannot account for the full spectrum of human creativity, with Sternberg having more serious reservations than Perkins. I argue in this commentary that while blind variation and selective retention (BVSR) may not be involved in all forms of human behavior and thought, Campbell has made a compelling (if often misunderstood) case that all genuine forms of human creativity and invention involve BVSR. To support this broad application of Campbell's theory, I argue for the complementarity of among-organism and within-organism BVSR as well as for the complementarity of prior and current BVSR in all forms of creative human endeavor.     

Control of a Virtual Avatar Influences Postural Activity and Motion Sickness

The influence of vehicular control on motion sickness has implications for theories of motion sickness etiology. We asked whether motion sickness susceptibility might also be related to the control of non-vehicular locomotion. Participants were exposed to a console video game that featured ambulatory locomotion of a virtual avatar. In a yoked control design, individuals either played the game (players) or watched another participant's recorded game play (viewers). Viewers were more likely than players to report motion sickness. During exposure to the video game players moved more than viewers, and the movement of players was more predictable or self-similar than the movement of viewers. Coupling of movement within player-viewer pairs was greater for pairs in which the viewer later reported motion sickness than for pairs in which both participants stated that they were not motion sick. The results reveal that motion sickness incidence can be influenced by the control of stimulus motion, in general, and is not limited to control of vehicular motion. We discuss implications of these findings for theories of motion sickness etiology.     

Advancing a family perspective in health research: models and methods

In this essay we review and respond to four problems that have impeded the application of family theory to health research: the difficulty in translating family concepts to empirical health research; the confusion and uncertainty in measuring "wholes" and "parts" of a family in a single health project; the apparent conflict between circular-causal and linear perspectives in model building; and the putative, implicit "violation" of a family perspective by the employment of certain data management and design strategies. We argue that current, complex conceptualizations of the family have to be matched with equally complex research designs and methods, and that techniques are available to reach these goals. We distinguish between theoretical models and research methods, and review several strategies, design issues, and alternatives for data analysis. Throughout, we point to 1) the need to maintain consistency among theory, construct, and indicator, 2) the employment of multidimensional family assessment in health research, and 3) the use of readily available but infrequently used methods and procedures for appreciating the richness of multivariate family data.     

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.     

Papier Mâché Problems in Epistemology: A Defense of Strong Internalism*

I attempt to persuade the reader that externalism admits of no plausible interpretation. I argue that reliability is a concept with very different contours from epistemic justification, and that attempts to explicate justification in terms of reliability must fail. I address several other forms of externalism, and also mixed forms of justification. I then argue that externalist theories of justification cannot close the gap between mere true belief and knowledge. I suggest that a fourth condition on knowledge is required, regardless of whether justification is internalist or externalist. I argue that with such a fourth condition a strong internalist theory of justification is adequate to the task that remains in making true belief knowledge. Additionally, strong internalism is more satisfying to our intuitions than externalism and mixed forms of justification. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Senses Considered as One Perceptual System

ABSTRACT

J. J. Gibson (1966) rejected many classical assumptions about perception but retained 1 that dates back to classical antiquity: the assumption of separate senses. We suggest that Gibson's retention of this assumption compromised his novel concept of perceptual systems. We argue that lawful, 1:1 specification of the animal–environment interaction, which is necessary for perception to be direct, cannot exist in individual forms of ambient energy, such as light, or sound. We argue that specification exists exclusively in emergent, higher order patterns that extend across different forms of ambient energy. These emergent, higher order patterns constitute the global array. If specification exists exclusively in the global array, then direct perception cannot be based upon detection of patterns that are confined to individual forms of ambient energy and, therefore, Gibson's argument for the existence of several distinct perceptual systems cannot be correct. We argue that the senses function as a single, irreducible perceptual system that is sensitive exclusively to patterns in the global array. That is, rather than distinct perceptual systems there exists only 1 perceptual system.     

Perceiving object motion using vision and touch

In a previous experiment, we showed that bistable visual object motion was partially disambiguated by tactile input. Here, we investigated this effect further by employing a more potent visuotactile stimulus. Monocular viewing of a tangible wire-frame sphere (TS) rotating about its vertical axis produced bistable alternations of direction. Touching the TS biased simultaneous and subsequent visual perception of motion. Both of these biases were in the direction of the tactile stimulation and, therefore, constituted facilitation or priming, as opposed to interference or adaptation. Although touching the TS biased visual perception, tactile stimulation was not able to override the ambiguous visual percept. This led to periods of sensory conflict, during which visual and tactile motion percepts were incongruent. Visual and tactile inputs can sometimes be fused to form a coherent percept of object motion but, when they are in extreme conflict, can also remain independent.     

Patterns of Conflict Resolution Within Relationships and Coercive Sexual Behavior of Men and Women

Conflict tactics within relationships and coercive sexual behavior are separate phenomena that are empirically related. To answer why they should be related, we drew upon two theoretical frameworks: an individualized form of cultural spillover and feminist control theory. Using an ANOVA framework, we constructed hypotheses through which we could (1) test for relations among constructs and (2) discriminate between the predictions of cultural spillover and feminist theory. We hypothesized that the severity of individuals' coercive sexual behavior would be related to the violence level of conflict tactics in relationships and also to a pattern of generalized psychological abuse within relationships. We also hypothesized that men, compared to women, would engage in more physically coercive sexual behavior and use more violence in conflict tactics. University students (50% women, 93% <23 years old, from a school with 73% White students) responded to the measures. With the exception of the last hypothesis, these predictions were supported by the overall data, although not universally within levels of gender. Based on the pattern of hypothesis confirmation and inconsistencies, we discuss the mix of support and potential moderators that would resolve inconsistencies for each theory.     

Stance Width Influences Postural Stability and Motion Sickness

We examined the influence of stance width (the distance between the feet) on postural sway and visually induced motion sickness. Stance width influences the magnitude of body sway, and changes in sway precede the subjective symptoms of motion sickness. Thus, manipulation of stance width may influence motion sickness incidence. Participants (healthy young adults) were exposed to complex, low-frequency oscillation of a moving room. Participants stood with their feet 5 cm, 17 cm, or 30 cm apart. During exposure to visual motion, the widest stance (30 cm) was associated with reduced incidence of motion sickness. For all stance widths, motion sickness was preceded by significant changes in motion of the head and torso. The results support the postural instability theory of motion sickness and suggest practical implications for the prevention of motion sickness. Adoption of wider stance may decrease the risk of motion sickness in operational situations.     

New perspectives in temperament/personality research: The “Behavioral” model of the Warsaw group

This paper reviews the theory and research of the Warsaw school of differential psychophysiology, which has modified and extended the typologic model constructed by Teplov and Nebylitsyn. While Soviet theory still favors a relatively inflexible structure of nervous system properties as the biologic basis of individual differences in personality, Strelau and colleagues, in line with the action/activity model of Vygotsky and Tomaszewski, begin with the premise that for every individual there is a specific, genetically determined optimal level of arousal, a necessary background for fullest emotional and intellectual development. The person strives to create this optimal climate through an active process of stimulation control, achieved primarily through enhancement or dampening of reactivity—which describes innate responsivity in the reacting systems to both sensory and emotional stimuli—through various hormonal ‘tuning’ mechanisms and through “appropriate” activity, reflected in different cognitive styles and preference for certain work conditions. Such activities aim to ensure comfortable physical and psychologic environments, in which the individual can avoid conflict and stress. The system regulating and integrating such control mechanisms is the core of personality. Investigations of the Warsaw group on relationships between reactivity and different forms of stimulation seeking/control—risk-taking, work style preferences, cognitive style, defense mechanisms, for example—and between reactivity and tolerance of stress and conflict and their speculations about the neurophysiologic and endocrinologic mechanisms of stimulation control are described, as are a number of questionnaires developed by this group to measure reactivity, the temporal parameters of response, and stimulation-seeking in a variety of occupational and social contexts.     

On the interpretation of the CHC factor Gc

On the one hand, the factors Gf and Gc in the Cattell-Horn-Carroll (CHC) model of intelligence are hypothesized to represent individual differences in unique psychological or biological capacities. On the other hand, they are interpreted as representing the theoretical variables fluid and crystallized intelligence in investment theory. With respect to Gc, this leads to a theoretical conflict because in investment theory crystallized intelligence is not a capacity but purely a statistical entity. We contend that if CHC factor Gc represents a capacity, it cannot represent crystallized intelligence, and if Gc represents crystallized intelligence, it does not represent a capacity. In addition, from our discussion of Gc, we conclude that in investment theory the factors Gf and g represent one and the same capacity. In support of our theoretical conclusions, we implemented the CHC model in a confirmatory factor analysis of a HCA (Human Cognitive Abilities project) data set. As expected, Gf and g were statistically indistinguishable. Gc was effectively absent, because it was statistically equivalent to verbal comprehension. Factors Gc and g could be removed from the model without any reduction in model fit. We argue that in the CHC taxonomy the factors Gc and g are redundant as explanatory variables.