Multiplicative effects of intention on the perception of bistable apparent motion

When viewing ambiguous displays, observers can, via intentional efforts, affect which perceptual interpretation they perceive. Specifically, observers can increase the probability of seeing the desired percept. Little is known, however, about how intentional efforts interact with sensory inputs in exerting their effects on perception. In two experiments, the current study explored the possibility that intentional efforts might operate by multiplicatively enhancing the stimulus-based activation of the desired perceptual representation. Such a possibility is suggested by recent neurophysiological research on attention. In support of this idea, when we presented bistable apparent motion displays under stimulus conditions differentially favoring one motion percept over the other, observers' intentional efforts to see a particular motion were generally more effective under conditions in which stimulus factors favored the intended motion percept.     

Symmetry and elongation of objects influence perceived direction of translational motion

Five experiments were conducted to examine how perceived direction of motion is influenced by aspects of shape of a moving object such as symmetry and elongation. Random polygons moving obliquely were presented on a computer screen and perceived direction of motion was measured. Experiments 1 and 2 showed that a symmetric object moving off the axis of symmetry caused motion to be perceived as more aligned with the axis than it actually was. However, Experiment 3 showed that motion did not influence perceived orientation of symmetry axis. Experiment 4 revealed that symmetric shapes resulted in faster judgments on direction of motion than asymmetric shapes only when the motion is along the axis. Experiment 5 showed that elongation causes a bias in perceived direction of motion similar to effects of symmetry. Existence of such biases is consistent with the hypothesis that in the course of evolution, the visual system has been adapted to regularities of motion in the animate world.     

Audiovisual bounce-inducing effect: When sound congruence affects grouping in vision

Two disks moving from opposite points in space, overlapping, and stopping at one another’s starting point can be seen as either bouncing off one another or streaming through one another. With silent displays, observers report streaming, whereas, if a sound is played when the disks are in the overlap region, observers report bouncing. The change in perception is thought to be modulated by a lack of attention that inhibits the integration of the motion signal when disks overlap and by the sound that increases the congruence of the display, in comparison with a real elastic bounce. Here, we accompanied the disks’ motion with either a bounce-congruent sound (a billiard ball) or with bounce-incongruent sounds (a water drop, a firework). When the sound was switched on 200 msec before the disks’ overlap, (1) all the audiovisual displays induced more bounce responses than did the silent display, but (2) the bounce-congruent sound induced more bounce responses than did the bounceincongruent sounds. However, when the sound was switched on at the disks’ overlap, only the first result was observed. These results highlight both the role of attention and that of sound congruence.     

Tachistoscopic display using color-lookup-table display devices

In this article, I describe a method for presenting multiple bit-mapped images on video displays under precise temporal control. The method makes use of the color-table animation technique that can be used with color-lookup-table display devices. The principal challenge in applying this technique to the display of multiple stimuli lies in dealing efficiently with the problem of overlapping displays. The solution described here is to allocate separate bit slices of screen memory to stimuli that overlap and to allocate sequential color-table indices to stimuli that are disjoint. Software is described that automatically computes the location of a stimulus on the screen, allocates color indices appropriately, transfers bit images to screen memory efficiently, and manipulates the color lookup table to present a given stimulus to the viewer. These operations are handled transparently; the user simply draws the stimuli and then turns them on or off under program control.     

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.     

Attentional Tracking in the Perception of Apparent Motion: Evidence from Sequential Blanking Displays

Perception of sequential blanking displays was studied in a series of three experiments investigating factors that influence whether “shadow motion” or “item motion” is seen in a display. In addition to the duration of the blanking interval (BI) itself, three other such factors were identified: the eccentricity at which the display is viewed, the spacing of items in the display, and the type of motion that subjects are instructed to try to see. It is argued that these and other previously reported results are explicable without the need to invoke any kind of visual integration period. Instead, they are interpreted in terms of a first-order system of automatic luminance detectors and a second-order tracking system involving both voluntary and involuntary attention. The relationship of these findings to other recent work in apparent motion and visual attention and to other bistable motion displays is discussed.     

Illusory figures based on local kinematics.

A new type of motion-induced illusory figure determined by local kinematic information is investigated. The new figure is induced by radial line patterns subjected to either figure motion (the lines change as if they were stationary and a triangle was rotating in front of them) or background motion (the lines change as if they were being rotated behind a stationary triangle). Although the two kinds of motion are equivalent from the viewpoint of relative displacements, perceptually they yield very different results. With background motion, observers tend to perceive rigid figures that have a triangular shape. With figure motion, observers report seeing deforming figures with shapes that vary depending on the number of lines in the display. We consider two alternative accounts for this asymmetry which we term the background superiority effect (BSE). The first account proposes that the effect is due to retinal persistence and to figure stability. Against this line of explanation, we demonstrate that observers also see rigid triangular shapes in displays where both the figure and the radial lines rotate (double motion displays). The second account proposes that the effect depends on the availability of local kinematic information constraining contour orientation. This second line of explanation is consistent with observers' reports of bowed edges in double motion displays rotating in phase or in counterphase. Candidate mechanisms for extracting local kinematic information are discussed.     

Perception of animacy from the motion of a single object

We demonstrate that a single moving object can create the subjective impression that it is alive, based solely on its pattern of movement. Our displays differ from conventional biological motion displays (which normally involve multiple moving points, usually integrated to suggest a human form) in that they contain only a single rigid object moving across a uniform field. We focus on motion paths in which the speed and direction of the target object change simultaneously. Naive subjects' ratings of animacy were significantly influenced by (i) the magnitude of the speed change, (ii) the angular magnitude of the direction change, (iii) the shape of the object, and (iv) the alignment between the principal axis of the object and its direction of motion. These findings are consistent with the hypothesis that observers classify as animate only those objects whose motion trajectories are otherwise unlikely to occur in the observed setting.     

时序知觉重复启动效应的作用机制

先前研究发现,时序判断任务在启动的靶刺激先出现时出现了重复启动效应的反转,这是以往的理论所不能单独解释的。通过两个实验对我们提出的双加工表征匹配调节假说加以实证检验,实验结果支持了该假说。因此,双加工表征匹配调节假说能较完整地综合解释时序知觉重复启动效应的作用机制     

Demonstrations of spatiotemporal integration and what they tell us about the visual system

Five sets of displays are presented on the journal website to be viewed in conjunction with the text. We concentrate on the factors that give rise to the integration and disruption of the direction of apparent motion in two-dimensional and three-dimensional space. In the first set of displays we examine what factors contribute to the integration and disruption of apparent motion in the Ramachandran/Anstis clustered bistable quartets. In the second set we examine what factors give rise to the perception of the direction of motion in rotating two-dimensional wheels and dots. In the third and fourth sets we examine how the depth cues of shading and disparity contribute to the perception of apparent motion of opaque displays, and to the perception of rotating unoccluded displays, respectively. In the fifth set we examine how the depth cue of motion parallax influences the perception of apparent motion. Throughout, we make inferences about the roles which various parallel pathways and cortical areas play in the perceptions produced by the displays shown.     

Attentional modulation in perception of visual motion events.

Identical visual targets moving across each other with equal and constant speed can be perceived either to bounce off or to stream through each other. This bistable motion perception has been studied mostly in the context of motion integration. Since the perception of most ambiguous motion is affected by attention, there is the possibility of attentional modulation occurring in this case as well. We investigated whether distraction of attention from the moving targets would alter the relative frequency of each percept. During the observation of the streaming/bouncing motion event in the peripheral visual field, visual attention was disrupted by an abrupt presentation of a visual distractor at various timings and locations (experiment 1; exogenous distraction of attention) or by the demand of an additional discrimination task (experiments 2 and 3; endogenous distraction of attention). Both types of distractions of attention increased the frequency of the bouncing percept and decreased that of the streaming percept. These results suggest that attention may facilitate the perception of object motion as continuing in the same direction as in the past.     

Perception of elliptic biological motion

We tested the ability of the mature visual system for discrimination between types of elliptic biological motion on the basis of event kinematics. Healthy adult volunteers were presented with point-light displays depicting elliptic motion when only a single dot, a moving point-light arm, or a whole point-light human figure was visible. The displays were created in accordance with the two-thirds power kinematic law (natural motion), whereas the control displays violated this principle (unnatural motion). On each trial, participants judged whether the display represented natural or unnatural motion. The findings indicate that adults are highly sensitive to violation of the two-thirds power kinematic law. Notably, participants can easily discriminate between natural and unnatural motions without recognising the stimuli, which suggests that people implicitly use kinematic information. Most intriguing, event recognition seems to diminish the capacity to judge whether event kinematics is unnatural. We discuss possible ways for a cross-talk between perception and production of biological movement, and the brain mechanisms involved in biological motion processing.     

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 onglobal 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 alocal ensemble of overlapping detectors). Thresholds depending on luminance contrast were measured for a generalized singleelement 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.     

Eye movement Responses of Repressors and Sensitizers to a stressful film

Groups scoring high, intermediate or low on the Byrne R-S Scale viewed an industrial accident film while horizontal eye movements were assessed by means of infrared corneal reflection. Neutral and stressful film segments were scored in terms of deviations from the center of the perceptual field (point of looking scores), and the standard deviations of these scores were calculated as an index of perceptual scanning. A stressful segment was also dichotically scored as to whether the point of looking was on or off dominant elements of the scene. Results indicated that Repressors and Sensitizers had equivalent levels of perceptual scanning (and both significantly higher than Intermediates' level) independent of film segment content, but that they differed in on/off and average point of looking for the stressful segment such that Repressors were avoiding stressful content. These data suggest that relatively high perceptual scanning can be an avoidant defensive style of attending to dynamic stimulus displays. The issue of adaptiveness of responding is considered.     

3-D graphics animation program for the Apple II

A graphics design program for creating point-light displays of transforming 3-D objects is presented. This program was written for an Apple II microcomputer interfaced to a Texas Instruments TMS 9918A video display processor. In contrast to other 3-D design programs, it uses individual point-lights undergoing circular trajectories as a design primitive. An editor enables the user to enter and edit specific motion parameters for defining the parallel projection of as many as 16 point-lights on the screen. These parameters are then used to calculate and store in an animation list the screen positions of each point-light for each frame. Number of frames to be displayed and display rate are user defined.     

Infants' representations of three-dimensional occluded objects

Infants' ability to represent objects has received significant attention from the developmental research community. With the advent of eye-tracking technology, detailed analysis of infants' looking patterns during object occlusion have revealed much about the nature of infants' representations. The current study continues this research by analyzing infants' looking patterns in a novel manner and by comparing infants' looking at a simple display in which a single three-dimensional (3D) object moves along a continuous trajectory to a more complex display in which two 3D objects undergo trajectories that are interrupted behind an occluder. Six-month-old infants saw an occlusion sequence in which a ball moved along a linear path, disappeared behind a rectangular screen, and then a ball (ball-ball event) or a box (ball-box event) emerged at the other edge. An eye-tracking system recorded infants' eye-movements during the event sequence. Results from examination of infants' attention to the occluder indicate that during the occlusion interval infants looked longer to the side of the occluder behind which the moving occluded object was located, shifting gaze from one side of the occluder to the other as the object(s) moved behind the screen. Furthermore, when events included two objects, infants attended to the spatiotemporal coordinates of the objects longer than when a single object was involved. These results provide clear evidence that infants' visual tracking is different in response to a one-object display than to a two-object display. Furthermore, this finding suggests that infants may require more focused attention to the hidden position of objects in more complex multiple-object displays and provides additional evidence that infants represent the spatial location of moving occluded objects.     

Contrast configuration influences grouping in apparent motion

We investigated whether the same principles that influence grouping in static displays also influence grouping in apparent motion. Using the Ternus display, we found that the proportion of group motion reports was influenced by changes in contrast configuration. Subjects made judgments of completion of these same configurations in a static display. Generally, contrast configurations that induced a high proportion of group motion responses were judged as more 'complete' in static displays. Using a stereo display, we then tested whether stereo information and T-junction information were critical for this increase in group motion. Perceived grouping was consistently higher for same contrast polarity configurations than for opposite contrast polarity configurations, regardless of the presence of stereo information or explicit T-junctions. Thus, while grouping in static and moving displays showed a similar dependence on contrast configuration, motion grouping showed little dependence on stereo or T-junction information.     

The case of the magic bones: Dogs’ memory of the physical properties of objects

Dogs’ memory for properties of occluded objects was assessed using a looking-time procedure. The looking-time procedure has been used to indicate that a change in expectation has been observed, with longer looking times associated with change as compared with no change. In our experiments, a bone-shaped dog biscuit (bone) was placed behind a horizontal screen that then rotated up to occlude the object before the screen returned to its horizontal position. Dogs were shown one of two test events. In one (congruent) event, the screen rotated up to obscure the bone and then rotated back down to reveal the unchanged bone. In the other (incongruent) event, the screen rotated up to obscure the bone and then rotated back down to reveal a bone that had changed in size (Experiment 1) or color (Experiment 2). Looking times were measured to assess which events represented the detection of a change. Increased looking time on incongruent trials indicated that the dogs remembered the size and color of the occluded object.     

Why anamorphoses look as they do: an experimental study

The aim of this research was to understand why anamorphic images break up until they are unrecognizable when the observer's eye moves away from the regularization point. An experimental device was set up allowing the anamorphic deformation of images, consisting of a rotating screen on which figures were projected. The point from which subjects observed the screen was far from the projecting point. The projected figures lengthened equally when the screen rotated either clockwise or counterclockwise. On the other hand, the perceptual result was the opposite: in the former case, a rigid figure was seen rotating around its own vertical axis; in the latter case, the same figure was seen elongating or shortening in a non-rigid manner, without rotating. Since we were in a projective condition, the invariance of the cross-ratio was maintained. Therefore, we were in a situation of non-rigidity, in spite of the invariance of the cross-ratio. Three stimuli, white on a black background, were used in experiment 1. They were a segment, three aligned points, and four aligned points. Subjects had to rotate the screen at will and stop it at the point when they saw the transformation of movement from rigid rotation to non-rigid elongation. The results showed that: (i) in spite of being a projective invariant, the cross-ratio is not always a perceptual invariant too; (ii) the threshold screen position between the two motions was located at the position where the modifications of the solid angle subtended to the stimulus assumed a different trend from that of a sinusoid. Two stimuli were used in experiment 2: a continuous segment and one intersected by four vertical lines. The aim was the same as for experiment 1, but subjects had to repeat it from five different points of observation. The results showed that: (1) there was no significant difference depending on type of stimulus, indicating that the computability of the cross-ratio is not a necessary condition for the execution of the task; (2) the more the observer moved away from the projection axis, the more evident the distortion of the stimulus appeared, in accordance with what happens when observing an anamorphosis; (3) when the metamorphosis from rigid motion to elastic motion was seen the visual angle subtended to the stimulus was constant for all distances from the projection axis, in accordance with the hypothesis of rigidity.