Representational momentum contributes to motion induced mislocalization of stationary objects

The influence of a moving target on memory for the location of a briefly presented stationary object was examined. When the stationary object was aligned with the final portion of the moving target's trajectory, memory for the location of the stationary object was displaced forward (i.e., in the direction of motion of the moving target); the magnitude of forward displacement increased with increases in the velocity of the moving target, decreased with increases in the distance of the stationary object from the final location of the moving target, and increased and then decreased with increases in retention interval. It is suggested that forward displacement in memory for a stationary object aligned with the final portion of a moving target's trajectory reflects an influence of representational momentum of the moving target on memory for the location of the stationary object. Implications of the data for theories of representational momentum and motion induced mislocalization are discussed.     

The effect of body posture on long-range time-to-contact estimation

On Earth, gravity accelerates freely moving objects downward, whereas upward-moving objects are being decelerated. Do humans take internalised knowledge of gravity into account when estimating time-to-contact (TTC, the time remaining before the moving object reaches the observer)? To answer this question, we created a motion-prediction task in which participants saw the initial part of an object's trajectory moving on a collision course prior to an occlusion. Observers had to judge when the object would make contact with them. The visual scene was presented with a head-mounted display. Participants lay either supine (looking up) or prone (looking down), suggestive of the ball either rising up or falling down toward them. Results showed that body posture had a significant effect on time-to-contact estimation, but only when occlusion times were long (2.5 s). The effect was also rather small. This lack of immediacy in the posture effect suggests that TTC estimation is initially robust toward the effect of gravity, which comes to bear only as more time is allowed for post-processing of the visual information.     

Time-to-contact judgments of an approaching object that is partially concealed by an occluder

Prior studies of time-to-contact (TTC) focused on judgments of unoccluded approaching objects. P. R. DeLucia, M. K. Kaiser, J. M. Bush, L. E. Meyer, and B. T. Sweet (2003) showed that partial occlusion decreases an object's optical size and expansion rate and that the value of tau derived from the reduced optical size (relative rate of accretion; RRA) does not necessarily correspond to TTC. In the present study, a computer-generated object approached the observer while unoccluded or partially concealed by a stationary or moving occluder. In some scenes, the occluder's motion nullified the object's optical expansion. Results indicated that stationary and moving occluders affected TTC judgments. RRA predicted directional changes in TTC judgments but predicted larger changes in such judgments than were observed. Tau did not predict effects of occlusion. When developing models of perceived collision, it is important to consider effects of partial occlusion on optical TTC information and on TTC judgments.     

The pointedness effect on representational momentum

An observer's memory for the final position of a moving object is shifted forward in the direction of that object's motion. It is called representational momentum (RM). This study addressed stimulus-specific effects on RM. In Experiment 1, participants showed larger memory shift for an object moving in its typical direction of motion than when it moved in a nontypical direction of motion. In Experiment 2, participants indicated larger memory shift for a pointed pattern moving in the direction of its point than when it moved in the opposite direction. In Experiment 3, we again examined the influences of knowledge about objects' typical motions and the pointedness of objects, because we did not control the shape (pointedness) of objects in Experiment 1. The results showed that only pointedness affected the magnitude of memory shift and that the effect was smaller than the momentum effect.     

Comparing mislocalizations with moving stimuli: The Fröhlich effect,the flash-lag,and representational momentum

When observers are asked to localize the onset or the offset position of a moving target, they typically make localization errors in the direction of movement. Similarly, when observers judge a moving target that is presented in alignment with a flash, the target appears to lead the flash. These errors are known as the Fröhlich effect, representational momentum, and flash-lag effect, respectively. This study compared the size of the three mislocalization errors. In Experiment 1, a flash appeared either simultaneously with the onset, the mid-position, or the offset of the moving target. Observers then judged the position where the moving target was located when the flash appeared. Experiments 2 and 3 are exclusively concerned with localizing the onset and the offset of the moving target. When observers localized the position with respect to the point in time when the flash was presented, a clear mislocalization in the direction of movement was observed at the initial position and the mid-position. In contrast, a mislocalization opposite to movement direction occurred at the final position. When observers were asked to ignore the flash (or when no flash was presented at all), a reduced error (or no error) was observed at the initial position and only a minor error in the direction of the movement occurred at the final position. An integrative model is proposed, which suggests a common underlying mechanism, but emphasizes the specific processing components of the Fröhlich effect, flash-lag effect, and representational momentum.     

Size-arrival effects: the potential roles of conflicts between monocular and binocular time-to-contact information, and of computer aliasing.

With computer simulations of self-motion, participants approached a floating object and tried to "jump" over it without collision. Participants "jumped" significantly later over small objects than they did over larger objects. This occurred when the displays were viewed monocularly or binocularly, a finding that suggests that such size-arrival effects (DeLucia & Warren, 1994) were not due to a conflict between monocular and binocular cues to time-to-contact (TTC) information (Tresilian, 1994, 1995). Moreover, the results further suggest that size-arrival effects are not due to irregularities in TTC information that can occur from computer aliasing and that the latter does not always affect TTC estimation; visual information used in such judgments does not seem to be extracted on a frame-by-frame basis.     

Size-arrival effects: The potential roles of conflicts between monocular and binocular time-to-contact information, and of computer aliasing

With computer simulations of self-motion, participants approached a floating object and tried to “jump” over it without collision. Participants “jumped” significantly later over small objects than they did over larger objects. This occurred when the displays were viewed monocularly or binocularly, a finding that suggests that such size-arrival effects (DeLucia & Warren, 1994) were not due to a conflict between monocular and binocular cues to time-to-contact (TTC) information (Tresilian, 1994,1995). Moreover, the results further suggest that size-arrival effects are not due to irregularities in TTC information that can occur from computer abasing and that the latter does not always affect TTC estimation; visual information used in such judgments does not seem to be extracted on a frame-by-frame basis.     

Threatening pictures induce shortened time-to-contact estimates

The ability to estimate the time remaining until collision occurs with an approaching object (time-to-collision, TTC) is crucial for any mobile animal. In the present study, we report three experiments examining whether higher level cognitive factors, represented by affective value of approaching objects, could affect judgments of TTC. A theory of TTC estimates based purely on the optical variable tau does not predict an influence of the affective value of an approaching object. In Experiments 1 and 2, we compared TTC estimates of threatening and neutral pictures that approached our participants on a screen and disappeared from view before a collision would have occurred. Images were taken from the International Affective Picture System. Threatening pictures??in particular, the picture of a frontal attack??were judged to collide earlier than neutral pictures. In Experiment 3, the approaching stimuli were faces with different emotional expressions. TTC tended to be underestimated for angry faces. We discuss these results, considering the roles of affective and cognitive mechanisms modulating TTC estimation and general time perception.     

Perceptual information and attentional constraints in visual search of collision events

This study examined the detection of collision events when multiple moving objects were present in the scene. Observers were presented with displays simulating a 3-D environment with multiple moving objects. The authors examined the ability of observers to detect collisions using a signal-detection paradigm and a visual search paradigm. The results indicated that, overall, observers were quite accurate at detecting collisions. Observers used both expansion information and static position to detect collisions, with expansion information being the more important source. Singleton search conditions were not processed in parallel, and conjunction search conditions had poorer performance than singleton search conditions. In addition, reaction times were greater for target-present trials as compared with target-absent trials. The results are interpreted in terms of 4 visual search hypotheses for collision detection when multiple moving objects are present.     

Anticipating action in complex scenes

In four experiments we explored the accuracy of memory for human action using displays with continuous motion. In Experiment 1, a desktop virtual environment was used to visually simulate ego‐motion in depth, as would be experienced by a passenger in a car. Using a task very similar to that employed in typical studies of representational momentum we probed the accuracy of memory for an instantaneous point in space/time, finding a consistent bias for future locations. In Experiment 2, we used the same virtual environment to introduce a new “interruption” paradigm in which the sensitivity to displacements during a continuous event could be assessed. Thresholds for detecting displacements in ego‐position in the direction of motion were significantly higher than those opposite the direction of motion. In Experiments 3 and 4 we extended previous work that has shown anticipation effects for frozen action photographs or isolated human figures by presenting observers with short video sequences of complex crowd scenes. In both experiments, memory for the stopping position of the video was shifted forward, consistent with representational momentum. Interestingly, when the video sequences were played in reverse, the magnitude of this forward bias was larger. Taken together, the results of all four experiments suggest that even when presented with complex, continuous motion, the visual system may sometimes try to anticipate the outcome of our own and others' actions.     

Intuitive physics: the straight-down belief and its origin

This study examines the nature and origin of a common misconception about moving objects. We first show through the use of pencil-and-paper problems that many people erroneously believe that an object that is carried by another moving object (e.g., a ball carried by a walking person) will, if dropped, fall to the ground in a straight vertical line. (In fact, such an object will fall forward in a parabolic arc.) We then demonstrate that this "straight-down belief" turns up not only on pencil-and-paper problems but also on a problem presented in a concrete, dynamic fashion (Experiment 1) and in a situation in which a subject drops a ball while walking (Experiment 2). We next consider the origin of the straight-down belief and propose that the belief may stem from a perceptual illusion. Specifically, we suggest that objects dropped from a moving carrier may be perceived as falling straight down or even backward, when in fact they move forward as they fall. Experiment 3, in which subjects view computer-generated displays simulating situations in which a carried object is dropped, and Experiment 4, in which subjects view a videotape of a walking person dropping an object, provide data consistent with this "seeing is believing" hypothesis.     

Object-based anisotropies in the flash-lag effect

The relative visual position of a briefly flashed stimulus is systematically modified in the presence of motion signals. We investigated the two-dimensional distortion of the positional representation of a flash relative to a moving stimulus. Analysis of the spatial pattern of mislocalization revealed that the perceived position of a flash was not uniformly displaced, but instead shifted toward a single point of convergence that followed the moving object from behind at a fixed distance. Although the absolute magnitude of mislocalization increased with motion speed, the convergence point remained unaffected. The motion modified the perceived position of a flash, but had little influence on the perceived shape of a spatially extended flash stimulus. These results demonstrate that motion anisotropically distorts positional representation after the shapes of objects are represented. Furthermore, the results imply that the flash-lag effect may be considered a special case of two-dimensional anisotropic distortion.     

表征动量的朝向效应

本研究通过4个实验探索运动物体的朝向对表征动量的影响。4个实验均使用了2(朝向：正向vs.倒向)×2(运动方向：左vs.右/上vs.下)两因素实验设计。前3个实验使用不同的刺激材料进行水平方向的诱导运动, 结果发现, 正向运动的前移量大于倒向运动的前移量, 但这种朝向效应仅仅作用于水平向右方向, 即运动方向水平向左时朝向效应消失。实验4将运动方向改为垂直运动, 结果发现, 正向运动的前移量大于倒向运动的前移量, 但这种朝向效应仅仅作用于垂直向下方向, 即运动方向垂直向上时朝向效应消失。结论：朝向影响表征动量, 但仅作用于水平向右和垂直向下方向上, 前者可能和阅读习惯有关, 后者可能和重力作用有关。     

飞行场景中表征动量的地标吸引效应和排斥效应

设置了安全和危险两种地标, 采用诱导运动范式考察了飞行场景中运动目标和关联地标的相对关系、目标运动方向及关联地标的意义特征和呈现时间对运动目标位置判断的影响。结果显示: (1)飞行场景中飞机的表征动量较强; (2) 趋近安全地标的表征动量大于远离安全地标的表征动量, 趋近危险地标的表征动量小于远离危险地标的表征动量, 安全地标呈现出地标吸引效应, 而危险地标呈现出地标排斥效应; (3) 高关联的安全和危险地标使飞机的表征动量不受运动方向影响; (4) 保持间隔期间呈现的安全和危险地标使飞机的表征动量增加。结论 :表征动量的地标效应受制于地标意义特征, 表征动量受到目标和地标之间的因果关系和情景意义的影响。     

The onset-repulsion effect and motion-induced mislocalization of a stationary object

The influence of a moving target on memory for the location of a briefly presented stationary object aligned with the initial location of that moving target was examined. Memory for the location of the stationary object was displaced backward (ie in the direction opposite to target motion), and memory for the initial location of the moving target was also displaced backward (consistent with an onset-repulsion effect); displacement of the stationary object did not differ from displacement of the moving target. Displacement in memory for the initial location of a moving target was not influenced by whether or not a stationary object aligned with that initial location was also presented. The results demonstrate that motion-induced mislocalization can occur in a direction other than the direction of motion, and are consistent with the hypothesis that dynamics of a moving target can influence memory for a nearby stationary object.     

Measuring causal perception: connections to representational momentum?

In a collision between two objects, we can perceive not only low-level properties, such as color and motion, but also the seemingly high-level property of causality. It has proven difficult, however, to measure causal perception in a quantitatively rigorous way which goes beyond perceptual reports. Here we focus on the possibility of measuring perceived causality using the phenomenon of representational momentum (RM). Recent studies suggest a relationship between causal perception and RM, based on the fact that RM appears to be attenuated for causally 'launched' objects. This is explained by appeal to the visual expectation that a 'launched' object is inert and thus should eventually cease its movement after a collision, without a source of self-propulsion. We first replicated these demonstrations, and then evaluated this alleged connection by exploring RM for different types of displays, including the contrast between causal launching and non-causal 'passing'. These experiments suggest that the RM-attenuation effect is not a pure measure of causal perception, but rather may reflect lower-level spatiotemporal correlates of only some causal displays. We conclude by discussing the strengths and pitfalls of various methods of measuring causal perception.     

The influence of spatial context and the role of intentionality in the interpretation of animacy from motion

We present three experiments investigating how spatial context influences the attribution of animacy to a moving target. Each of our displays contained a moving object (the target) that might, depending on the way it moved, convey the impression that it was alive (animate). We investigated the mechanisms underlying this attribution by manipulating the nature of the spatial context surrounding the target. In Experiment 1, the context consisted of a simple static dot (the foil), whose position relative to the target's trajectory was manipulated. With some foil positions--for example, when the foil was lying along the path traveled by the target--animacy judgments were elevated relative to control foil locations, apparently because this context supported the impression that the target was "reacting to" or was in some other way mentally influenced by the foil. In Experiment 2, contexts consisted of a static oriented rectangle (the "paddle"). On some trials, the target collided with the paddle in a way that seemed to physically account for the target's motion pattern (in the sense of having imparted momentum to it); this condition reduced animacy ratings. Experiment 3 was similar, except that the paddles themselves were in motion; again, animacy attribution was suppressed when the target's motion seemed to have been caused by a collision with the paddle. Hence, animacy attributions can be either elevated or suppressed by the nature of the environment and the target's interaction with it. Animacy attribution tracks intentionality attribution; contrary to some earlier proposals, we conclude that attributing animacy involves, and may even require, attributing to the target some minimal mental capacity sufficient to endow the target with intentionality.     

Illusory motion and representational momentum

When a moving target vanishes abruptly, participants judge its final position as being ahead of its actual final position, in the direction of motion (representational momentum; Freyd & Finke, 1984). In the present study, we presented illusory motion and examined whether or not forward displacement was affected by the perceived direction and speed of the target. Experiments 1A and 1B showed that an illusory direction of movement of a target was perceived, and Experiment 2 showed that an illusory speed of a moving target was observed. However, neither the direction nor the magnitude of forward displacement was affected by these illusions. Therefore, it was suggested that the mechanism underlying forward displacement (or some extrapolation processing) uses different motion signals than does the perceptual mechanism.     

时间结构和速度线索对碰撞时间估计的影响

估计被遮挡的运动物体何时到达某一特定位置被称为碰撞时间估计,本研究利用遮挡范式,通过控制时间结构、物理速度及运动过程是否可见设计两个2（物理速度）×3（时间结构）实验来探究三者对碰撞时间估计的影响。结果：当时间结构一致时,不论物理速度快慢及是否存在视觉速度线索,被试的绩效都没有显著差异;当时间结构不一致时,不论物理速度快慢,存在视觉速度条件下被试的绝对偏差小于无视觉速度条件。结论：时间结构一致时,被试主要使用时间线索进行碰撞时间估计;时间结构不一致时,被试通过整合时间结构和视觉速度线索进行估计。     

Optical Specification of Time-to-Contact for a Spectator

In the article, we provide an account of the informational basis underlying judgments of time-to-contract (TTC) under the conditions examined in Kim, Effken, and Carello (1998), in which observers watched collisions between 2 objects from various vantage points, over varying collision paths, and with additional observer movement. First, we examine the informational candidates proposed by Bootsma and his colleagues (e.g., Bootsma & Oudejans, 1993) and by Tresilian (1990). Simulation results showed that these models do not accurately describe TTc for such varying conditions. We present an alternative model, emphasizing the advantages of body scaling. Our model applied this scaling to the vertical gap between edges of the opposing surfaces of each object. Because all model terms are expressed in eyeheight units, distortions that occurred in the other models due to polar injection are eliminated. The proposed model provided veridical estimates of TTC for straight-line collision cases over a variety of viewing angles and with the addition of observer movement, but not for collisions along circular paths, in which the model only approximated TTC values.