Paradoxical perception of object identity in visual motion (original) (raw)
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Perceptual grouping in space and time: Evidence from the Ternus display
Perception & Psychophysics, 1997
We report three experiments investigating the effect of perceptual grouping on the appearance of a bistable apparent-motion (Ternus) display. Subjects viewed a Ternus display embedded in an array of context elements that could potentially group with the Ternus elements. In contrast to several previous findings, we found that grouping influenced apparent motion perception. In Experiment 1, apparent motion perception was significantly affected via grouping by shape similarity, even when the visible persistence of the elements was controlled. In Experiment 2, elements perceived as moving without context were perceived as stationary without context were perceived as moving when grouped with moving elements perceived as stationary without context were perceived as moving when grouped with moving context elements. We argue that grouping in the spatial and temporal domains interact to yield perceptual experience of apparent-motion displays.
Perceptual grouping in the Ternus display: evidence for an `association field' in apparent motion
Vision Research, 2002
We present psychophysical experiments designed to reveal the role of facilitative contour interactions (the so-called 'association field') in apparent motion. We use the Ternus display (a trio of horizontally aligned elements oscillating in apparent motion). This display is perceived in 'element' motion when interframe intervals (IFIs) are short, and in 'group' motion when IFIs are long. Using Gabor elements arranged collinearly or in parallel, IFI is varied to find group motion thresholds. Consistent with a role for collinearity in perceptual grouping, thresholds are lower for collinear displays. The collinear vs. parallel comparison is made while manipulating contrast, spatial frequency, eccentricity, phase, orientation jitter and element separation. Results show a clear effect of contrast not observed in lateral masking paradigms or in 'pathfinder' stimuli, with higher contrast promoting within-frame grouping, and evidence of facilitatory interactions among parallel elements (although over a smaller scale). The tendency for collinear displays to group more than parallel displays declined with eccentricity with no clear difference evident at 12 deg. These changes in group motion thresholds indicate changing association strengths among the elements and is accounted for in terms of an association field. Alternative accounts in terms of second-order collector units or visible persistence are considered but are not supported by the data. Ó
Motion perception induced by dynamic grouping: a probe for the compositional structure of objects
Vision research, 2012
A new method is described for determining how the visual system resolves ambiguities in the compositional structure of multi-surface objects; i.e., how the surfaces of objects are grouped together to form a hierarchical structure. The method entails dynamic grouping motion, a high level process in which changes in a surface (e.g., increases or decreases in its luminance, hue or texture) transiently perturb its affinity with adjacent surfaces. Affinity is determined by the combined effects of Gestalt and other grouping variables in indicating that a pair of surfaces forms a subunit within an object's compositional structure. Such pre-perturbation surface groupings are indicated by the perception of characteristic motions across the changing surface. When the affinity of adjacent surfaces is increased by a dynamic grouping variable, their grouping is transiently strengthened; the perceived motion is away from their boundary. When the affinity of adjacent surfaces is decreased, the...
A Failure of the Proximity Principle in the Perception of Motion
Humana.Mente. Journal of Philosophical Studies
The proximity principle is a fundamental fact of spatial vision. It has been a cornerstone of the Gestalt approach to perception, it is supported by overwhelming empirical evidence, and its utility has been proven in studies of the ecological statistics of optical stimulation. We show, however, that the principle does not generalize to dynamic scenes, i.e., no /spatiotemporal/ proximity principle governs the perception of motion. In other words, elements of a dynamic display separated by short spatiotemporal distances are not more likely to be perceived as parts of the same object than elements separated by longer spatiotemporal distances.
Perceptual organization and neural computation
Journal of Vision
Our present understanding of perceptual organization has its roots in the observations and qualitative principles of the Gestalt psychologists. Gestaltists and their associates identified and classified phenomena that reflect how perceptual systems derive representations of the environment based on fragmentary information and stimulus context. A broad range of phenomena was explored in this early work. The perceptual organization of visual motion was a major focus, involving both simple (Korte, 1915; Ternus, 1936; von Schiller, 1933; Wertheimer, 1912) and complex (Duncker, 1929; Musatti, 1924; Rubin, 1927; Wallach, 1935) motion patterns. The perceptual organization of static form was explored in studies of part–whole relationships in simple planar figures (Rubin, 1915; Wertheimer, 1923/1938) and later in studies of illusory contours and amodal completion (Kanizsa, 1955; Michotte, Thinès, & Crabbé, 1964). Additional topics included lightness and color phenomena (Benary, 1924; Gelb, 1929; Katz, 1935; Wallach, 1948) and the perception of events (Michotte, 1941). In brief, the research areas addressed by the first generations of Gestalt psychologists spanned much of what is now vision science. The broad impact of Gestalt ideas is reflected in the exceptional scope of this special issue.
Perceptual grouping impairs temporal resolution
Experimental Brain Research, 2007
Performance on multisensory temporal order judgment (TOJ) tasks is enhanced when the sensory stimuli are presented at diVerent locations rather than the same location. In our Wrst experiment, we replicated this result for spatially separated stimuli within the visual modality. In Experiment 2, we investigated the eVect of perceptual grouping on this spatial eVect. Observers performed a visual TOJ task in which two stimuli were presented in a conWguration that encouraged perceptual grouping or not (i.e., one-and two-object conditions respectively). Despite a constant spatial disparity between targets across the two conditions, a smaller just noticeable diVerence (i.e., better temporal resolution) was found when the two targets formed two objects than when they formed one. This eVect of perceptual grouping persisted in Experiment 3 when we controlled for apparent motion by systematically varying the spatial distance between the targets. Thus, in contrast to the putative same-object advantage observed in spatial discrimination tasks, these Wndings indicate that perceptual grouping impairs visual temporal resolution.
Attention, Perception, & Psychophysics, 2010
We investigated the combined effects of perceptual grouping cues (proximity and contour closure/proximity and orientation similarity) on object representation, using motion-induced blindness, a phenomenon in which salient visual stimuli perceptually disappear when surrounded by moving patterns. We presented as visual targets two stimuli in which a solid square was embedded in an outlined square. Participants reported whether the targets disappeared independently or simultaneously. The results showed that a relatively high proximity cue (with a 0.2-deg separation between the targets) modulated the perceptions of the independent or simultaneous disappearances of targets, regardless of other grouping cues. The contour closure cue modulated these disappearances in the 0.4-to 0.8-deg separations. Finally, the orientation similarity cue began to modulate these disappearances in the 0.6-to 0.8-deg separations. We suggest that the separation between the visual stimuli modulates the combined effects of perceptual grouping cues on complete object representation.
Spatial versus temporal grouping in a modified Ternus display
Vision research, 2007
The Ternus display can induce a percept of 'element motion' or 'group motion'. Conventionally, this has been attributed to two different motion processes, with different spatial and temporal ranges. In contrast, recent studies have emphasised spatial and temporal grouping principles as underlying the apparent motion percepts in the Ternus display. The present study explored effects of spatial and temporal grouping on the apparent motion percept in a novel Ternus display of oriented Gabor elements with no inter-frame interval. Each frame of this stimulus could be further divided into 'sub-frames', and the orientation of the carriers was changed across these sub-frames. In four experiments transitions were found between the motion percepts with changes in orientation across time (Experiment 1) and space (Experiment 2), and with a temporal offset in the orientation change of the outer element (Experiment 3) to the extent that group motion was not perceived even with large orientation changes over time that previously led to group motion (Experiment 4). Collectively, these results indicate that while spatial properties have an influence in determining the percept of the Ternus display, temporal properties also have a strong influence, and can override spatial grouping. However, these temporal effects cannot be attributed to spatiotemporal limits of low-level motion processes. Some aspects of the observed spatial grouping effects can be accounted for in terms of a modified association field, which may occur through connectivity of orientation selective units in V1. The temporal effects observed are considered in terms of temporal integration, the transitional value at a temporal offset of 40 ms being remarkably similar to psychophysical and neurophysiological estimates of the peak temporal impulse response. These temporal responses could be detected at a higher level in the system, providing a basis for apparent motion perception.
Motion accumulates while movement disappears: spatial interactions in visual motion
2014
When objects move, they change position over time. However, the mechanisms in human vision that could be capable of tracking these changes in position are not well understood. I constructed stimuli that combined a first-order carrier motion with a position-defined envelope movement. When viewed in the periphery, the appearance of motion was very sensitive to changes in position of its envelope, regardless the amount of carrier motion. However, when multiple motion elements were placed close together, the appearance of the stimulus came to be dominated by its carrier motion. When elements were added, sensitivity to position-defined motion decreased at the same time as the sensitivity to first-order motion increased; visual clutter thus favors first-order motion over position-defined motion. These effects are modeled in terms of two mechanisms that each contribute to motion appearance. The first-order mechanism sums motion over larger areas of space without regard to their position; in the presence of clutter, it sums all signals together. The position-defined mechanism tracks the change in location of isolated features; it cannot pool signals over space and works best with salient, uncluttered objects. This mechanism suffers crowding when flankers are introduced. While first-order motion is understood in terms of spatiotemporal filtering, position-defined motion might be viewed as a feature integration problem, involving the comparison of successive positions over time. These systems have a subtractive interaction that may serve to locate objects that are moving differently from their background. Complementary characteristics and limitations of the two systems each play roles in the perception of moving objects.