Timothy L. Hubbard

Representational momentum and related displacements in spatial memory: A review of the findings

Memory for the final location of a moving target is often displaced in the direction of target motion, and this has been referred to asrepresentational momentum. Characteristics of the target (e.g., velocity, size, direction, and identity), display (e.g., target format, retention interval, and response method), context (landmarks, expectations, and attribution of motion source), and observer (e.g., allocation of attention, eye movements, and psychopathology) that influence the direction and magnitude of displacement are reviewed. Specific conclusions regarding numerous variables that influence displacement (e.g., presence of landmarks or surrounding context), as well as broad-based conclusions regarding displacement in general (e.g., displacement does not reflect objective physical principles, may reflect aspects of naive physics, does not solely reflect eye movements, may involve some modular processing, and reflects high-level processes) are drawn. A possible computational theory of displacement is suggested in which displacement (1) helps bridge the gap between perception and action and (2) plays a critical part in localizing stimuli in the environment.

Judged displacement in apparent vertical and horizontal motion

The judged vanishing point of a target traveling along a vertical or horizontal trajectory at uniform velocity was examined. In Experiments 1 and 2, subjects indicated the vanishing point by positioning a cross hair. Judged vanishing point was displaced forward in the direction of motion, and the magnitude of the displacement increased with the apparent velocity of the target. Displacement was greater for horizontal than for vertical motion. In Experiment 3, similar patterns were found using a forced-choice paradigm. Experiments 4 and 5 assessed the role of knowledge of the target’s likely behavior. In Experiment 4, the target bounced within the confines of a square frame. Judged vanishing point was displaced in the anticipated direction, even 9 when the anticipated direction was opposite to the current path of motion. Experiment 5 was a control experiment that ruled out the presence of the frame as the sole cause for displacement. The results suggest that displacement from the true vanishing point is due to a high-level cognitive mechanism capable of utilizing knowledge about probable target location.

Auditory Imagery: Empirical Findings.

The empirical literature on auditory imagery is reviewed. Data on (a) imagery for auditory features (pitch, timbre, loudness), (b) imagery for complex nonverbal auditory stimuli (musical contour, melody, harmony, tempo, notational audiation, environmental sounds), (c) imagery for verbal stimuli (speech, text, in dreams, interior monologue), (d) auditory imagerys relationship to perception and memory (detection, encoding, recall, mnemonic properties, phonological loop), and (e) individual differences in auditory imagery (in vividness, musical ability and experience, synesthesia, musical hallucinosis, schizophrenia, amusia) are considered. It is concluded that auditory imagery (a) preserves many structural and temporal properties of auditory stimuli, (b) can facilitate auditory discrimination but interfere with auditory detection, (c) involves many of the same brain areas as auditory perception, (d) is often but not necessarily influenced by subvocalization, (e) involves semantically interpreted information and expectancies, (f) involves depictive components and descriptive components, (g) can function as a mnemonic but is distinct from rehearsal, and (h) is related to musical ability and experience (although the mechanisms of that relationship are not clear).

Cognitive representation of linear motion: Possible direction and gravity effects in judged displacement

The judged vanishing point of a target undergoing apparent motion in a horizontal, vertical, or oblique direction was examined. In Experiment 1, subjects indicated the vanishing point by positioning a crosshair. Judged vanishing point was displaced forward in the direction. of motion, with the magnitude of displacement being largest for horizontal motion, intermediate for oblique motion, and smallest for vertical motion. In addition, the magnitude of displacement increased with faster apparent velocities. In Experiment 2, subjects judged whether a stationary probe presented after the moving target vanished was at the same location where the moving target vanished. Probes were located along the axis of motion, and probes located beyond the vanishing point evidenced a higher probability of asame response than did probes behind the vanishing point. In Experiment 3, subjects judged whether a stationary probe presented after the moving target vanished was located on a straight-line extension of the path of motion of the moving target. Probes below the path of motion evidenced a higher probability of asame response than did probes above the path of motion for horizontal and ascending oblique motion; probes above the path of motion evidenced a higher probability for asame response than did probes below the path of motion for descending oblique motion. Overall, the pattern of results suggests that the magnitude of displacement increases as proximity to a horizontal axis increases, and that in some conditions there may be a component analogous to a gravitational influence incorporated into the mental representation.

Target Size and Displacement Along the Axis of Implied Gravitational Attraction: Effects of Implied Weight and Evidence of Representational Gravity

Effects of target size on displacements between the actual and remembered vanishing points of moving and stationary targets were examined. For horizontally or vertically moving targets, target size influenced displacement only along the axis aligned with the direction of implied gravitational attraction; larger targets exhibited greater downward displacement when targets moved horizontally, greater forward displacement when targets descended, and smaller forward displacement when targets ascended. For stationary targets, target size did not influence displacement along the axis aligned with the direction of implied gravitational attraction. The data are consistent with the hypothesis that mental representation incorporates an analogue of weight. It is proposed that weight, rather than mass, influences displacement because the representational system incorporates subjective or experiential aspects of physical principles rather than physical principles per se. An observer who perceives a target that is moving in a consistent direction will usually remember that target as having traveled slightly further than it actually did; in other words, memory for the final orientation or location of a target will be slightly displaced in the direction of anticipated target motion (for a review, see Hubbard, 1995b).

Representational Momentum and Michotte's (1946/1963) "Launching Effect" Paradigm

In A. Michottes (1946/1963) launching effect, a moving launcher contacts a stationary target, and then the launcher becomes stationary and the target begins to move. In this experiment, observers viewed modifications of a launching effect display, and displacement in memory for the location of targets was measured. Forward displacement of targets in launching effect displays was decreased relative to that of targets (a) that were presented in isolation and either moved at a constant fast or slow velocity or decelerated or (b) that moved in a direction orthogonal to previous motion of the launcher. Possible explanations involving a deceleration of motion or landmark attraction effects were ruled out. Displacement patterns were consistent with naive impetus theory and the hypothesis that observers believed impetus from the launcher was imparted to the target and then dissipated.

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

In Michottes (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.

Is judged displacement a modular process

Memory for the final position of a circular target undergoing apparent motion in a horizontal, vertical, or oblique direction (Hubbard, 1990) or for the final orientation of a rectangle undergoing implied rotation in a consistent clockwise or counterclockwise direction (Freyd & Finke, 1984; Kelly & Freyd, 1987) is shifted forward in the direction of anticipated motion. Furthermore, the magnitude of the memory shift is related to the apparent or implied velocity of the stimulus (Freyd & Finke, 1985; Hubbard & Bharucha, 1988), direction of motion of both the stimulus (Hubbard, 1990) and the context (Hubbard, 1993b), constancy of stimulus shape (Kelly & Freyd, 1987), duration of the retention interval (Freyd & Johnson, 1987), coherence of inducing sequence (Freyd & Finke, 1984), similarity of the final stimulus to a prototypical member of a category (Kelly & Freyd, 1987) or sche-

The effect of context on visual representational momentum

Effects of background context on representational momentum -were examined in six experiments. In each experiment, three orientations of a target rectangle undergoing implied rotation (i.e., the inducing stimuli) were presented, and subjects judged whether the orientation of a fourth rectangle (i.e., the probe) was the same as or different from that of the third inducing stimulus. Target rectangles were enclosed within a larger square frame context during induction (i.e., presentation of the inducing stimuli), judgment (i.e., presentation of the probe), or both induction and judgment. If context during induction moved in the same direction as the inducing stimuli or if context during judgment was rotated slightly forward from the orientation of the final inducing stimulus, representational momentum was increased. If context during induction moved in the direction opposite to the inducing stimuli or if context during judgment was rotated slightly backward from the orientation of the final inducing stimulus, representational momentum was decreased or reversed. If context was present during both induction and judgment, direction of representational momentum was biased toward the context at judgment Implications of context for accounts of representational momentum are discussed, and a tentative model is proposed.

Representational momentum, centripetal force, and curvilinear impetus

In 3 experiments, observers witnessed a target moving along a circular orbit and indicated the location at which the target vanished. The judged vanishing point was displaced forward in the direction of implied momentum and inward in the direction of implied centripetal force. In general, increases in either the angular velocity of the target or the radius length of the orbit increased the magnitude of forward displacement. If both angular velocity and radius length were varied, then increases in either angular velocity or radius length also increased the magnitude of inward displacement. The displacement patterns were consistent with hypotheses that analogues of momentum and centripetal force were incorporated into the representational system. A framework is proposed that accounts for (a) the forward and inward displacements and (b) naive-physics data on the spiral tube problem previously interpreted as suggesting a belief in a naive curvilinear-impetus principle.