Configural processing in the perception of apparent biological motion.

In classic demonstrations of apparent motion, observers typically report seeing motion along the shortest possible path between 2 sequentially presented objects. However, when realistic photographs of a human body are sequentially presented at slow temporal rates, observers report paths of apparent motion that arc consistent with the movement limitations of the human body even when those paths are not the shortest possible. The current set of experiments examined those aspects of the human form that lead to the perception of biomechanically consistent paths of motion. The authors' findings suggest that the perception of apparent biological motion extends to human movements that involve inanimate objects. The authors also report that observers can perceive apparent motion of nonbiological objects in a manner similar to apparent motion of human bodies. However, a global hierarchy of orientation and position cues resembling the human form is required for the perception of these paths. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical dynamics of visual motion perception: Short-range and long-range apparent motion.

Describes further evidence for a new neural network theory of biological motion perception. The theory clarifies why parallel streams V1→V2, V1→MT, and V1→V2→MT exist for static form and motion form processing among the areas V1, V2, and MT of visual cortex. It also suggests that the static form system generates emergent boundary segmentations whose outputs are insensitive to direction-of-contrast and to direction-of-motion, whereas the motion form system generates emergent boundary segmentations whose outputs are insensitive to direction-of-contrast but sensitive to direction-of-motion. Data on short- and long-range apparent motion percepts are explained including beta, split, gamma and reverse-contrast gamma, and delta motions, as well as visual inertia. Also included are the transition from group motion to element motion in response to a Ternus display as the interstimulus interval (ISI) decreases; group motion in response to a reverse-contrast Ternus display even at short ISIs; speed-up of motion velocity as interflash distance increases or flash duration decreases dependence of the transition from element motion to group motion on stimulus duration and size, various classical dependencies between flash duration, spatial separation, ISI, and motion threshold known as Korte's laws; dependence of motion strength on stimulus orientation and spatial frequency; short-range and long-range form–color interactions; and binocular interactions of flashes to different eyes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Counter-changing luminance: A non-Fourier, nonattentional basis for the perception of single-element apparent motion.

Motion perception was studied for generalized apparent motion stimuli composed of 2 simultaneously visible elements whose luminance alternated between 2 values (only 1 element is visible at a time for standard apparent motion). It was demonstrated that 1st-order motion energy is neither necessary nor sufficient for the perception of apparent motion. Instead, it was found that counter-changing luminance--simultaneous luminance changes at 2 element locations--is the informational basis for perceiving luminance-defined apparent motion: Motion starts where luminance changes toward the background luminance value and ends where luminance changes away from the background luminance. The results were not attributable to either 2nd-order motion mechanisms (for which rectification precedes the computation of motion energy) or attention-based, 3rd-order motion mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object continuity in apparent motion and attention.

Presents 2 experiments that show that the continuity property may underlie 2 seemingly unrelated perceptual phenomena: attentional capture by abrupt visual onset and the appearance of bistable apparent motion displays. In Exp 1, 30 Ss reported the appearance of a bistable apparent-motion (or Ternus) display and engaged in visual search for a prespecified target; on each trial 1 element was briefly flickered off and back on. The time course of the gap duration effect in the visual search task was very similar to that for the Ternus display. In Exp 2, with 15 Ss, the possibility that the presence of an abrupt offset caused the results of Exp 1 was ruled out, since the reactions times (RTs) for the single- and double-offset conditions were similar. Results suggest that the interruption of spatiotemporal continuity may be the underlying mechanism that produces these 2 seemingly unrelated perceptual phenomena. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamic, state-dependent thresholds for the perception of single-element apparent motion: bistability from local cooperativity

Previous studies have indicated that the formation of coherent patterns for multielement motion displays depends on global cooperative interactions among large ensembles of spatially distributed motion detectors. These interactions enhance certain motion directions and suppress others. It is reported here that perceiving one element moving between two nearby locations likewise is subject to cooperative influences (possibly facilitating and inhibiting interactions within a local ensemble of overlapping detectors). Thresholds depending on luminance contrast were measured for a generalized single-element apparent-motion stimulus, and evidence for spontaneous switching and hysteresis effects indicated that motion perception near the 50% threshold was bistable. That is, for conditions in which motion and nonmotion were perceived half the time, the two percepts were distinct; when one was perceived, it clearly was discriminable from the other. These results indicated that (1) single-element apparent-motion thresholds depended on the immediately preceding state of the ensemble of motion detectors responding to the stimulus, and (2) the stimulus activation of individual motion detectors always might be influenced by recurrent, cooperative interactions resulting from the detectors' being embedded within interconnected ensembles.     

The two-process distinction in apparent motion.

Traces the historical development of the notion that two processes mediate apparent motion percepts, examines evidence regarding their existence, and summarizes associated characteristics. The short-range process is assumed to reflect the activity of low-level directionally selective motion detectors, have a relatively small spatial integration range, and be favored by short stimulus durations and interstimulus intervals. The long-range process is thought to reflect higher order perceptual activity, match stimulus elements over relatively large retinal distances, and be favored by longer stimulus durations and interstimulus intervals. Criteria for associating different percepts with functionally different processes are advanced and applied. The theoretical status of the two-process distinction is examined, and a heuristic model of motion perception is presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bistability and hysteresis in the organization of apparent motion patterns.

In a paradigm for which 2 distinct patterns are perceived for the same stimulus, perceptual hysteresis (persistence of a percept despite parameter change to values favoring the alternative pattern) and temporal stability (persistence despite intrinsic propensities toward spontaneous change) are interdependent. Greater persistence during parameter change reduces temporal stability, slowing the rate of parameter change reduces hysteresis by increasing opportunity for spontaneous change, and increasing temporal stability (by enlarging the stimulus) increases hysteresis. Hysteresis results in the perception of parametrically disfavored patterns; a parameter can influence a percept without specifying it. The visual system thus exhibits time-dependent behavior analogous to dynamical behavior observed in other systems, both physical and biological, for which there is competition among alternative patterns that vary in relative stability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial attention and audiovisual interactions in apparent motion.

In this study, the authors combined the cross-modal dynamic capture task (involving the horizontal apparent movement of visual and auditory stimuli) with spatial cuing in the vertical dimension to investigate the role of spatial attention in cross-modal interactions during motion perception. Spatial attention was manipulated endogenously, either by means of a blocked design or by predictive peripheral cues, and exogenously by means of nonpredictive peripheral cues. The results of 3 experiments demonstrate a reduction in the magnitude of the cross-modal dynamic capture effect on cued trials compared with uncued trials. The introduction of neutral cues (Experiments 4 and 5) confirmed the existence of both attentional costs and benefits. This attention-related reduction in cross-modal dynamic capture was larger when a peripheral cue was used compared with when attention was oriented in a purely endogenous manner. In sum, the results suggest that spatial attention reduces illusory binding by facilitating the segregation of unimodal signals, thereby modulating audiovisual interactions in information processing. Thus, the effect of spatial attention occurs prior to or at the same time as cross-modal interactions involving motion information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The perception of depth through motion.

Motion perspective is the phenomenon that as an object moves, the projections of its surface features and of its contours undergo certain regular transformations. The retinal image undergoes similar transformations. This aspect of depth perception has received comparatively little attention. Theory has been primarily based on gestalt formulations, and, more recently, an empirical approach has been suggested which is based on the use of high speed computers. The latter approach appears quite promising. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depth perception in motion parallax and stereokinesis.

Perceived depth in the stereokinetic effect (SKE) illusion and in the monocular derivation of depth from motion parallax were compared. Motion parallax gradients of velocity can be decomposed into 2 components: object- and observer-relative transformations. SKE displays present only the object-relative component. Observers were asked to estimate the magnitude and near–far order of depth in motion parallax and SKE displays. Monocular derivation of depth magnitude from motion parallax is fully accounted for by the perceptual response to the SKE, and observer-relative transformations absent in the SKE are of perceptual utility only as determinants of the near–far signing of perceived sequential depth. The amount of depth and rigidity perceived in motion parallax and SKE displays covaries with the projective size of the stimuli. The monocular derivation of depth from motion is mediated by a perceptual heuristic of which the SKE is symptomatic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned stimulation in space and motion perception.

Argues that in the perception of distance, depth, and visual motion, a single property is often represented by 2 or more stimuli. Two instances of such redundant stimulation are discussed: (a) the various stimuli that represent visual motion and (b) the 2 forms of stimulation by which binocular parallax evokes stereoscopic depth perception. In the case of visual motion, simultaneous operation of redundant stimulation has raised questions concerning the basis of experienced motion and the conditions under which different motion processes are combined. Experiments are described that suggest that some redundant stimuli owe their existence to simple associative learning. Evidence is reviewed that shows that binocular parallax causes stereoscopic depth by means of 2 different perceptual processes. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pulfrich effect and the filling in of apparent motion

In the stroboscopic version of the Pulfrich effect a filter is able to induce depth shifts in a target as if the latter were moving continuously, rather than merely occupying a series of discrete positions. This was examined in a further series of experiments, in which a visual alignment technique was used to measure the perceived visual direction of an apparently moving target in intervals between its presentations. Results showed that the target has approximately the visual direction that it would have if it were moving continuously. This "filling in" of apparent motion was shown to occur before the level of stereopsis. The possible influence of tracking eye movements is discussed.     

Models of stimulus uncertainty in motion perception.

Proposed a model to account for the loss in visibility of moving targets that occurs when an observer is uncertain about the target's direction of motion. In response to uncertainty about 2 possible directions of motion, the observer is assumed to use a mechanism whose peak sensitivity is to a direction midway between the 2 possible directions. Seven experiments (observers were 7 naive Ss and the 1st author), using both reaction time and forced-choice data, demonstrate the predictive advantages of this midway model over competing single-band and multiple-band models. The experiments reveal several new properties of human motion perception: (a) direction and velocity information have orthogonal representations in the visual system; (b) although motion sensitivity does not vary with direction, the precision with which small changes in direction can be recognized does, reflecting differential breadth of tuning for directionally selective mechanisms sensitive to various directions; and (c) motion-analyzing mechanisms are broadly tuned for direction as well as speed. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of short- and long-range apparent motion in visual search.

The visual search paradigm was used in four experiments to investigate apparent motion perception. The addition of distractor items led to a linear increase in reaction time (RT) under long-range (LR) conditions (>35 min of arc displacement), whereas RT was independent of display size under short-range (SR) conditions (     

Orientation-dependent priming effects in the perception of biological motion.

In a serial 2-choice reaction time (RT) task, Ss discriminated between a biological motion walker and a similar distractor. The point-light walker appeared in 1 of 2 possible in-depth orientations: The figure was walking either to the right or to the left in the sagittal plane. Reliable priming effects were established in consecutive trials but only when priming and primed walkers had the same in-depth orientation. This orientation-dependent priming effect was not tempered when priming and primed figures had different directions of articulatory motion (Exps 1–6), different starting positions in the step cycle (Exp 2), different point-light localizations (Exp 3), or when the figures were translating (Exps 4–6). The data converge with neurophysiological findings that suggest that object recognition is accomplished by accessing high-level, orientation-dependent representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vector analysis and process combination in motion perception.

Conducted 3 experiments with 102 undergraduates that support an altered explanation of the vector analysis that occurs in certain motion displays discovered by G. Johansson (1950). What seemed the result of a perceptual vector analysis is ascribed to the outcome of 2 independent stimulus conditions—configural change and S-relative—to which such displays can give rise because of external vector analysis. In 2 of Johansson's displays, conditions for configurational change were altered by adding stationary reference points in the surround of the displays. Veridical perception of the displays resulted in a majority of instances. It was also found that the different motions that resulted from configurational change and from S-relative stimulation could combine to form unitary perceived motions and that this happened frequently under some conditions. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Accuracy and precision of binocular 3-D motion perception.

In principle, information for 3-D motion perception is provided by the differences in position and motion between left- and right-eye images of the world. It is known that observers can precisely judge between different 3-D motion trajectories, but the accuracy of binocular 3-D motion perception has not been studied. The authors measured the accuracy of 3-D motion perception. In 4 different tasks, observers were inaccurate, overestimating trajectory angle, despite consistently choosing similar angles (high precision). Errors did not vary consistently with target distance, as would be expected had inaccuracy been due to misestimates of viewing distance. Observers appeared to rely strongly on the lateral position of the target, almost to the exclusion of the use of depth information. For the present tasks, these data suggest that neither an accurate estimate of 3-D motion direction nor one of passing distance can be obtained using only binocular cues to motion in depth. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The visual perception of objective motion and subjective movement.

(This reprinted article originally appeared in Psychological Review, 1954, Vol 61, 304–314. The following abstract of the original article appeared in PA, Vol 29:5103.) The question of movement involves at least 3 closely related questions: How do we see the motion of an object? How do we see the stability of the environment? How do we perceive ourselves as moving in a stable environment? The author draws together the experimental evidence on the 3 questions and draws out its implications, including a hypothesis for research. The article concludes with a discussion of the requirements for a psychophysics of kinetic impressions. 19 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object and observer motion in the perception of objects by infants.

Sixteen-week-old human infants distinguish optical displacements given by their own motion from displacements given by moving objects, and they use only the latter to perceive the unity of partly occluded objects. Optical changes produced by moving the observer around a stationary object produced attentional levels characteristic of stationary observers viewing stationary displays and much lower than those shown by stationary observers viewing moving displays. Real displacements of an object with no subject-relative displacement, produced by moving an object so as to maintain a constant relation to the moving observer, evoked attentional levels that were higher than with stationary displays and more characteristic of attention to moving displays, a finding suggesting detection of the real motion. Previously reported abilities of infants to perceive the unity of partly occluded objects from motion information were found to depend on real object motion rather than on optical displacements in general. The results suggest that object perception depends on registration of the motions of surfaces in the three-dimensional layout. (PsycINFO Database Record (c) 2010 APA, all rights reserved)