Representational Momentum Beyond Internalized Physics

Abstract— Prediction of future motion is necessary in order to successfully deal with moving objects. Implicit measures have been used to evaluate the sources of information used in this task. For instance, observers may be asked to localize the final position of a moving target. Judgments have been found to be displaced in the direction of motion (forward displacement), suggesting that observers have internalized a mental analogue of physical momentum. However, more recent studies have shown that forward displacement may not be caused by cognitive mechanisms alone. Rather, predictive mechanisms at the perceptual and motor levels may contribute to the forward error. Supporting the notion that mechanisms of anticipation may be embodied, the forward error was found to depend on the execution of eye and pointing movements. Also, forward displacement depended on the motion type that was presented (smooth vs. jerky or implied), which suggests that attention moves to the next expected target position to facilitate responses to this position.     

Environmental invariants in the representation of motion: Implied dynamics and representational momentum,gravity, friction,and centripetal force

Memory for the final position of a moving target is often shifted or displaced from the true final position of that target. Early studies of this memory shift focused on parallels between the momentum of the target and the momentum of the representation of the target and called this displacementrepresentational momentum, but many factors other than momentum contribute to the memory shift. A consideration of the empirical literature on representational momentum and related types of displacement suggests there are at least four different types of factors influencing the direction and magnitude of such memory shifts: stimulus characteristics (e.g., target direction, target velocity), implied dynamics and environmental invariants (e.g., implied momentum, gravity, friction, centripetal force), memory averaging of target and nontarget context (e.g., biases toward previous target locations or nontarget context), and observers’ expectations (both tacit and conscious) regarding future target motion and target/context interactions. Several theories purporting to account for representational momentum and related types of displacement are also considered.     

A matter of design: No representational momentum without predictability

When observers are asked to localize the final position of a moving target, a forward shift of the judged final position is observed. So far, the forward shift has been attributed to the influence of mental continuation of the final target position (representational momentum). However, studies investigating forward displacement have used highly predictable target motion. The direction of target motion and the final target position were often varied between subjects. Thus, observers may have expected the target to travel in a particular direction or vanish at a particular location before a given trial started. In this study, direction of motion and final position were treated as fixed or random factors. The forward shift and the reversal of the shift with time (memory averaging) were absent when both factors were randomized. Thus, the forward shift with implied motion is restricted to repeatedly observed motion sequences that allow for pre-trial motion prediction.     

Does representational momentum reflect a distortion of the length or the endpoint of a trajectory?

Observers viewed a moving target, and after the target vanished, indicated either the initial position or the final position of the target. In Experiment 1, an auditory tone cued observers to indicate either the initial position or the final position; in Experiment 2, different groups of observers indicated the initial position or the final position. Judgments of the initial position were displaced backward in the direction opposite to motion, and judgments of the final position were displaced forward in the direction of motion. The data suggest that the remembered trajectory is longer than the actual trajectory, and the displacement pattern is not consistent with the hypothesis that representational momentum results from a distortion of memory for the location of a trajectory.     

线索呈现的时空特性对表征动量的影响

为揭示注意对表征动量的影响机制,我们结合线索提示和表征动量范式,通过两个实验比较高、低相关线索分别在诱导期间与保持间隔呈现对表征动量的影响,结果发现：(1)高相关线索的时间特性主效应不显著,最终位置均发生边缘性的向前偏移。(2)低相关线索呈现在诱导期间时,表征动量显著;呈现在保持间隔时,发生向后偏移。这些表明,随着注意增大,表征动量减小;高相关线索更有利于定位,而低相关线索易受时间特性的影响。研究结果验证表征动量的双加工理论。     

Shifting the start: backward mislocation of the initial position of a motion

Participants asked to judge the final position of a moving target typically indicate a position shifted forward. In the 6 experiments reported here, participants were asked to indicate both the starting position (SP) and the vanishing position (VP) at the onset and offset of a moving target. Results confirmed the forward displacement of the VP and showed a backward displacement of the SP. To test whether perceptual estimation was influenced by curvature of the trajectory, curvilinear motions were also used. Results showed that apparent displacements are along the geometrical tangents to the SP and VP. Relationships between the results and other findings such as the flash-lag effect the representational momentum, and the Fr?hlich effect are discussed.     

线索提示对表征动量的影响

研究结合线索提示和表征动量范式,实验1、2均采用2有无线索(有线索,无线索)×4诱导期间时距(1250ms,1750ms,2250ms,2750ms)混合实验设计,探讨线索呈现的加工阶段和时距对表征动量的影响。实验1恒定保持间隔时距,在不同时距的诱导期间呈现线索,发现线索主效应不显著,但表征动量呈减小趋势;时距主效应不显著。实验2变化诱导时距,在恒定的保持间隔呈现线索,发生向后偏移现象,线索主效应显著;时距主效应不显著。研究结果表明,随着注意的增加,表征动量效应减小;注意时距不显著影响表征动量,而注意阶段显著影响表征动量。研究结果为表征动量的双加工理论提供了实证支持。     

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.     

Larger forward memory displacement in the direction of gravity

An observer's memory for the final position of a moving stimulus is shifted forward in the direction of its motion. Observers in an upright posture typically show a larger forward memory displacement for a physically downward motion than for a physically upward motion of a stimulus (representational gravity; Hubbard & Bharucha, 1988). We examined whether representational gravity occurred along the environmentally vertical axis or the egocentrically vertical axis. In Experiment 1 observers in either upright or prone postures viewed egocentrically upward and downward motions of a stimulus. Egocentrically downward effects were observed only in the upright posture. In Experiment 2 observers in either upright or prone postures viewed approaching and receding motions of a stimulus along the line of sight. Only in the prone posture did the receding motion produce a larger forward memory displacement than the approaching motion. These results indicate that representational gravity depends not on the egocentric axis but on the environmental axis.     

Attention maintains mental extrapolation of target position: irrelevant distractors eliminate forward displacement after implied motion

Observers' judgments of the final position of a moving target are typically shifted in the direction of implied motion ("representational momentum"). The role of attention is unclear: visual attention may be necessary to maintain or halt target displacement. When attention was captured by irrelevant distractors presented during the retention interval, forward displacement after implied target motion disappeared, suggesting that attention may be necessary to maintain mental extrapolation of target motion. In a further corroborative experiment, the deployment of attention was measured after a sequence of implied motion, and faster responses were observed to stimuli appearing in the direction of motion. Thus, attention may guide the mental extrapolation of target motion. Additionally, eye movements were measured during stimulus presentation and retention interval. The results showed that forward displacement with implied motion does not depend on eye movements. Differences between implied and smooth motion are discussed with respect to recent neurophysiological findings.     

质量表征和眼动过度追踪对表征动量的影响

人们对运动目标最终位置的记忆常常会向运动方向发生偏移, 这种偏移被称为“表征动量”。现有研究对表征动量的解释涉及从低水平的知觉加工到高水平的认知加工等多个方面。本研究采用不同材质和滚动声音的球体作为刺激材料, 考察高水平的质量表征对表征动量的影响以及知觉水平的眼动信息在其中的作用。实验1探讨了对目标质量的主观表征对眼动追踪和表征动量的影响。结果显示, 质量表征会同时影响眼动追踪和表征动量。实验2通过不同的提示线索控制眼动追踪, 进一步探讨眼动过度追踪对表征动量的影响。我们发现, 非自然追踪的条件下, 表征动量会减小, 且质量表征对表征动量的影响不再显著。本研究结果表明, 高水平的质量表征对表征动量的影响会通过知觉水平的眼动过度追踪起作用; 然而, 表征动量还受其它因素影响, 眼动信息并非决定表征动量的唯一因素。     

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。     

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.     

Spatial memory and explicit knowledge: an effect of instruction on representational momentum

Freyd (1987; Finke & Freyd, 1985) suggested that representational momentum (i.e., forward displacement in memory for the location of a moving target) is impervious to error feedback (i.e., is modular or cognitively impenetrable), but studies supporting this claim might not have allowed sufficient opportunity for learning to occur. In the experiment reported here, participants were (a) naive regarding representational momentum, (b) informed about representational momentum but not instructed to counteract it, or (c) informed about representational momentum and instructed to counteract it. All participants exhibited significant displacement. However, participants informed about representational momentum exhibited less forward displacement than did naive participants due to a greater tendency to respond same to probes behind the true--same position. Possible mechanisms of compensation and the notion that displacement reflects both modular (cognitively impenetrable) and nonmodular (cognitively penetrable) components are addressed.     

Spatial memory and explicit knowledge: An effect of instruction on representational momentum

Freyd (1987; Finke & Freyd, 1985) suggested that representational momentum (i.e., forward displacement in memory for the location of a moving target) is impervious to error feedback (i.e., is modular or cognitively impenetrable), but studies supporting this claim might not have allowed sufficient opportunity for learning to occur. In the experiment reported here, participants were (a) naïve regarding representational momentum, (b) informed about representational momentum but not instructed to counteract it, or (c) informed about representational momentum and instructed to counteract it. All participants exhibited significant displacement. However, participants informed about representational momentum exhibited less forward displacement than did naïve participants due to a greater tendency to respond same to probes behind the true–same position. Possible mechanisms of compensation and the notion that displacement reflects both modular (cognitively impenetrable) and nonmodular (cognitively penetrable) components are addressed.     

The locus of "memory displacement" is at least partially perceptual: effects of velocity,expectation, friction,memory averaging,and weight

When observers are asked to localize the final position of a moving target, the judged position is usually displaced from the actual position. It has been suggested that mental processes derived from a number of invariant and noninvariant principles produce the mislocalization in memory. In this study, the effects of velocity, expectation, friction, memory averaging, and weight were reconsidered, and evidence was accumulated that supports the alternative view that the distortions arise to a large degree at a perceptual level. Effects of velocity and expectation were present when observers still perceived a persisting image of the target. It is suggested that the active reorienting of the perceptual organs explains the distortions. Furthermore, distortions of the perceived center of a visible stimulus may explain effects that have previously been attributed to memory averaging and mental analogues of weight. Thus, the locus of memory displacement is at least partially perceptual.     

Localization of moving sound

The final position of a moving sound source usually appears to be displaced in the direction of motion. We tested the hypothesis that this phenomenon, termed auditory representational momentum, is already emerging during, not merely after, the period of motion. For this purpose, we investigated the localization of a moving sound at different points in time. In a dark anechoic environment, an acoustic target moved along the frontal horizontal plane. In the initial, middle, or final phase of the motion trajectory, subjects received a tactile stimulus and determined the current position of the moving target at the moment of the stimulus by performing either relative-judgment or pointing tasks. Generally, in the initial phase of the auditory motion, the position was perceived to be displaced in the direction of motion, but this forward displacement disappeared in the further course of the motion. When the motion stimulus had ceased, however, its final position was again shifted in the direction of motion. The latter result suggests that representational momentum in spatial hearing is a phenomenon specific to the final point of motion. Mental extrapolation of past trajectory information is discussed as a potential source of this perceptual displacement.     

A possible role of naïve impetus in Michotte's "launching effect": Evidence from representational momentum

In Michotte's (1946/1963) launching effect paradigm, a moving launcher contacts a stationary target, and then the launcher becomes stationary and the target begins to move. In the experiments reported here, observers were presented with modifications of a launching effect display, and displacement in memory for targets was measured. Faster launcher velocities resulted in larger displacements for moving targets, and the effect of launcher velocity was larger with faster target velocities. Launcher velocity did not influence displacement of targets that remained stationary after contact. Increases in the distance travelled by moving targets after contact from the launcher resulted in smaller displacements. Displacement appeared to result from an expectation that impetus would be imparted from the launcher rather than from contact between the launcher and the target. Displacement patterns were consistent with naïve impetus theory and with the hypothesis that observers believed impetus from the launcher was imparted to the target and dissipated with subsequent target motion.     

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.     

Displacement in depth: Representational momentum and boundary extension

Memory for targets moving in depth and for stationary targets was examined in five experiments. Memory for targets moving in depth was displaced behind the target with slower target velocities (longer ISIS and retention intervals) and beyond the target with faster target velocities (shorter ISIS and retention intervals), and the overall magnitude of forward displacement for motion in depth was less than the overall magnitude of forward displacement for motion in the picture plane. Memory for stationary targets was initially displaced away from the observer, but memory for smaller stationary targets was subsequently displaced toward the observer and memory for larger stationary targets was subsequently displaced away from the observer; memory for the top or bottom edge of a stationary target was displaced inside the target perimeter. The data are consistent with Freyd and Johnson's (1987) two-component model of the time course of representational momentum and with Intraub et al.'s (1992) two-component model of boundary extension.