Contributions of visual and embodied expertise to body perception

Recent research has demonstrated that our perception of the human body differs from that of inanimate objects. This study investigated whether the visual perception of the human body differs from that of other animate bodies and, if so, whether that difference could be attributed to visual experience and/or embodied experience. To dissociate differential effects of these two types of expertise, inversion effects (recognition of inverted stimuli is slower and less accurate than recognition of upright stimuli) were compared for two types of bodies in postures that varied in typicality: humans in human postures (human-typical), humans in dog postures (human-atypical), dogs in dog postures (dog-typical), and dogs in human postures (dog-atypical). Inversion disrupts global configural processing. Relative changes in the size and presence of inversion effects reflect changes in visual processing. Both visual and embodiment expertise predict larger inversion effects for human over dog postures because we see humans more and we have experience producing human postures. However, our design that crosses body type and typicality leads to distinct predictions for visual and embodied experience. Visual expertise predicts an interaction between typicality and orientation: greater inversion effects should be found for typical over atypical postures regardless of body type. Alternatively, embodiment expertise predicts a body, typicality, and orientation interaction: larger inversion effects should be found for all human postures but only for atypical dog postures because humans can map their bodily experience onto these postures. Accuracy data supported embodiment expertise with the three-way interaction. However, response-time data supported contributions of visual expertise with larger inversion effects for typical over atypical postures. Thus, both types of expertise affect the visual perception of bodies.     

The indispensability of precollision kinematics in the visual perception of relative mass

The visible kinematic pattern that occurs when objects collide contains information about the relative mass of the objects. Recently, Gilden and Proffitt (1989) have claimed that perceivers are limited to the use of simultaneous elemental cues and that therefore mass discrimination judgments are independent of whether the precollision epoch is visible or not. The present paper argues that their experimental results are irrelevant because crucial parameters were held constant, and that false conclusions were drawn because their data were not treated for what they are: threshold measurements obtained with the method of constant stimuli. Three experiments are reported, showingthat a high level of performance is attainable only when the whole event is visible, and thus that the effective information is extended over time. In addition, modified PROBIT analysis was used to determine what information observers use when the precollision epoch is occluded. Analytically complex invariants, based on vector components in the abstract collision-axis system, proved to have the best fit to the data. Thus the elementaristic premises in Gilden and Proffitt’s cue-heuristic model for relative mass perception are defeated.     

Contributions of oral and extraoral facial movement to visual and audiovisual speech perception

Seeing a talker's face influences auditory speech recognition, but the visible input essential for this influence has yet to be established. Using a new seamless editing technique, the authors examined effects of restricting visible movement to oral or extraoral areas of a talking face. In Experiment 1, visual speech identification and visual influences on identifying auditory speech were compared across displays in which the whole face moved, the oral area moved, or the extraoral area moved. Visual speech influences on auditory speech recognition were substantial and unchanging across whole-face and oral-movement displays. However, extraoral movement also influenced identification of visual and audiovisual speech. Experiments 2 and 3 demonstrated that these results are dependent on intact and upright facial contexts, but only with extraoral movement displays.     

The limits of visual mass perception

The theory of direct perception suggests that observers can accurately judge the mass of a box picked up by a lifter shown in a point-light display. However, accurate perceptual performance may be limited to specific circumstances. The purpose of the present study was to systematically examine the factors that determine perception of mass, including display type, lifting speed, response type, and lifter's strength. In contrast to previous research, a wider range of viewing manipulations of point-light display conditions was investigated. In Experiment 1, we first created a circumstance where observers could accurately judge lifts of five box masses performed by a lifter of average strength. In Experiments 2–5, we manipulated the spatial and temporal aspects of the lift, the judgement type, and lifter's strength, respectively. Results showed that mass judgement gets worse whenever the context deviates from ideal conditions, such as when only the lifted object was shown, when video play speed was changed, or when lifters of different strength performed the same task. In conclusion, observers' perception of kinetic properties is compromised whenever viewing conditions are not ideal.     

Identifying the information for the visual perception of relative phase

The production and perception of coordinated rhythmic movement are very specifically structured. For production and perception, 0 degree mean relative phase is stable, 180 degrees is less stable, and no other state is stable without training. It has been hypothesized that perceptual stability characteristics underpin the movement stability characteristics, which has led to the development of a phase-driven oscillator model (e.g., Bingham, 2004a, 2004b). In the present study, a novel perturbation method was used to explore the identity of the perceptual information being used in rhythmic movement tasks. In the three conditions, relative position, relative speed, and frequency (variables motivated by the model) were selectively perturbed. Ten participants performed a judgment task to identify 0 degree or 180 degrees under these perturbation conditions, and 8 participants who had been trained to visually discriminate 90 degrees performed the task with perturbed 90 degrees displays. Discrimination of 0 degree and 180 degrees was unperturbed in 7 out of the 10 participants, but discrimination of 90 degrees was completely disrupted by the position perturbation and was made noisy by the frequency perturbation. We concluded that (1) the information used by most observers to perceive relative phase at 0 degree and 180 degrees was relative direction and (2) becoming an expert perceiver of 90 degrees entails learning a new variable composed of position and speed.     

Categorical perception of relative orientation in visual object recognition

The purpose of the present investigation was to determine whether the orientation between an object's parts is coded categorically for object recognition and physical discrimination. In three experiments, line drawings of novel objects in which the relative orientation of object parts varied by steps of 30 degrees were used. Participants performed either an object recognition task, in which they had to determine whether two objects were composed of the same set of parts, or a physical discrimination task, in which they had to determine whether two objects were physically identical. For object recognition, participants found it more difficult to compare the 0 degrees and 30 degrees versions and the 90 degrees and 60 degrees versions of an object than to compare the 30 degrees and 60 degrees versions, but only at an extended interstimulus interval (ISI). Categorical coding was also found in the physical discrimination task. These results suggest that relative orientation is coded categorically for both object recognition and physical discrimination, although metric information appears to be coded as well, especially at brief ISIs.     

Contributions of parvocellular and magnocellular pathways to visual perception near the hands are not fixed,but can be dynamically altered

Visual perception is altered near the hands, and several mechanisms have been proposed to account for this, including differences in attention and a bias toward magnocellular-preferential processing. Here we directly pitted these theories against one another in a visual search task consisting of either magnocellular- or parvocellular-preferred stimuli. Surprisingly, we found that when a large number of items are in the display, there is a parvocellular processing bias in near-hand space. Considered in the context of existing results, this indicates that hand proximity does not entail an inflexible bias toward magnocellular processing, but instead that the attentional demands of the task can dynamically alter the balance between magnocellular and parvocellular processing that accompanies hand proximity.     

Asymmetries in categorization, cerceptual discrimination, and visual search for reference and nonreference exemplars

In two experiments, we examined the representation, treatment, and attention devoted to the members of reference (i.e., club members) and nonreference (i.e., not club members) categories. Consistent with prior work on category interrelatedness (e.g., Goldstone, 1996; Goldstone, Steyvers, and Rogosky, 2003), the findings reveal the existence of asymmetric representations for reference and nonreference categories, which, however, decreased as expertise and familiarity with the categories increased (Experiments 1 and 2). Participants also more readily judged two reference exemplars as being the same than they did two nonreference exemplars (Experiment 1) and were better at detecting reference than nonreference exemplars in a set of novel, category-unspecified exemplars (Experiment 2). These findings provide evidence for the existence of a feature asymmetry in the representation and treatment of exemplars from reference and nonreference categories. Membership in a reference category acts as a salient feature, thereby increasing the perceived similarity and detection of faces that belong in the reference, in comparison with the nonreference, category.     

Development of the perception of invariants: substance and shape

Three experiments investigated the perception of substance and shape as invariant properties of objects by three-month-old infants. In experiment 1, infants were habituated to two differently shaped objects undergoing a rigid motion. After habituation of the infants, the objects were presented undergoing a different rigid motion, or undergoing a deforming motion, or undergoing the same rigid motion. Habituation was maintained to the new rigid motion, indicating that the two rigid motions were perceived as sharing an invariant property. Dishabituation, on the other hand, occurred when a deforming motion followed a rigid one. In experiment 2, infants were habituated to one shape undergoing two different rigid motions. After habituation, the shape was changed but the same two motions continued. Dishabituation occurred, compared to a group with no shape change, indicating that shape is distinguished as an invariant property over two rigid motions. In experiment 3, habituation to a shape undergoing two rigid motions was followed by a new shape presented motionless, or the same shape presented motionless. Cessation of motion did not prevent recognition of shape as invariant. Two properties of an object, substance and shape, thus appear to be detectable as invariant in an event sequence, an instance of "phenomenal doubling" at an early age.     

Experience, context, and the visual perception of human movement

Why are human observers particularly sensitive to human movement? Seven experiments examined the roles of visual experience and motor processes in human movement perception by comparing visual sensitivities to point-light displays of familiar, unusual, and impossible gaits across gait-speed and identity discrimination tasks. In both tasks, visual sensitivity to physically possible gaits was superior to visual sensitivity to physically impossible gaits, supporting perception-action coupling theories of human movement perception. Visual experience influenced walker-identity perception but not gait-speed discrimination. Thus, both motor experience and visual experience define visual sensitivity to human movement. An ecological perspective can be used to define the conditions necessary for experience-dependent sensitivity to human movement.     

Relative clause structure, relative clause perception, and the change from SOV to SVO.

This study presents a view of diachronic change in language, according to which one of the fundamental factors motivating syntactic change is to be found in the conflicting interaction of principles determining the language organization. Specifically, it will be argued that principles of structural nature and principles of perceptual nature are in conflict in languages of the SOV type, because of the relative clause construction. The way in which a relative clause is structured in an SOV language is an obstacle to its effective perceptual processing. It will be argued that this conflict is one of the major factors determining the diachronic change of a language from an OV to a VO typology.     

Functional representations common to visual perception and imagination

Subjects determined whether probe dots appearing in component squares of a 5 X 5 grid fell on a figure that, depending on the condition, was (a) visually presented as a pattern of darkened squares, (b) only remembered from a preceding presentation of such a pattern, or (c) imaginally generated from a verbal code. The speed and accuracy of the responses to the probes as well as the functional dependencies of the reaction times on structural variables were essentially the same whether the figural pattern was imagined, remembered, or actually seen. Reaction times averaged between 400 and 500 msec and were consistently faster (a) for on-figure than for off-figure responses, (b) for simpler figures that had fewer squares, (c) for off-figure probes that were more distant from the figure, and (d) for on-figure probes that consisted either of more dots on the figure or of a dot at the intersection of a horizontal and a vertical bar. The reults were consistent with a model in which a subject's perceptual or imaginal representations of these forms contain barlike units that respond independently to the probes.     

Eye movements and the integration of visual memory and visual perception

Because visual perception has temporal extent, temporally discontinuous input must be linked in memory. Recent research has suggested that this may be accomplished by integrating the active contents of visual short-term memory (VSTM) with subsequently perceived information. In the present experiments, we explored the relationship between VSTM consolidation and maintenance and eye movements, in order to discover how attention selects the information that is to be integrated. Specifically, we addressed whether stimuli needed to be overtly attended in order to be included in the memory representation or whether covert attention was sufficient. Results demonstrated that in static displays in which the to-be-integrated information was presented in the same spatial location, VSTM consolidation proceeded independently of the eyes, since subjects made few eye movements. In dynamic displays, however, in which the to-be-integrated information was presented in different spatial locations, eye movements were directly related to task performance. We conclude that these differences are related to different encoding strategies. In the static display case, VSTM was maintained in the same spatial location as that in which it was generated. This could apparently be accomplished with covert deployments of attention. In the dynamic case, however, VSTM was generated in a location that did not overlap with one of the to-be-integrated percepts. In order to "move" the memory trace, overt shifts of attention were required.     

The minimum principle and the perception of absolute,common, and relative motions

Wheel-generated motions have served as a touchstone for discussion of the perception of wholes and parts since the beginning of Gestalt psychology. The reason is that perceived common motions of the whole and the perceived relative motions of the parts are not obviously found in the absolute motion paths of points on a rolling wheel. In general, two types of theories have been proposed as to how common and relative motions are derived from absolute motions: one is that the common motions are extracted from the display first, leaving relative motions as the residual; the other is that relative motions are extracted first leaving common motions as the residual. A minimum principle can be used to defend both positions, but application of the principle seems contingent on the particular class of stimuli chosen. We propose a third view. It seems that there are at least two simultaneous processes—one for common motions and one for relative motions—involved in the perception of these and other stimuli and that a minimum principle is involved in both. However, for stimuli in many domains the minimization of relative motion dominates the perception. In general, we propose that any given stimulus can be organized to minimize the complexity of either its common motions or its relative motions; that which component is minimized depends on which of two processes reaches completion first (that for common or that for relative motions); and that the similarity of any two displays depends on whether common or relative motions are minimized.     

The relative contribution of relative height, linear perspective, and texture gradients to pictorial depth perception in 7-month-old infants

In the current preferential-reaching experiments, 7-month-olds were tested for their ability to respond to a combination of relative height and texture gradients. The infants were presented with a display in which these pictorial depth cues specified that two toys were at different distances. The experimental displays differed from the textured surfaces employed in earlier studies in that linear perspective of the contours of the texture elements was omitted. Experiment A shows that the infants still preferred to reach for the apparently nearer toy under monocular, but not binocular, viewing conditions, indicating that they responded to the pictorial depth cues. In experiment B, relative height and texture provided the infants with conflicting information for depth. Here, relative height outperformed texture information. A statistical comparison between the experiments as well as systematic comparisons with experimental conditions from an earlier study (Hemker et al, 2010 Infancy 15 6-27) revealed that texture gradients, unlike linear perspective, neither enhanced nor weakened the effect exerted by relative height. In sum, 7-month-old infants are obviously more sensitive to relative height and to the linear perspective of the surface contours than to the texture gradients of compression, perspective, and density.