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PubMed1987

The Ames window illusion: perception of illusory motion by human infants.

The sensitivity of human infants, 5 1/2-9 months of age, to the illusory oscillation of the Ames window was assessed in three experiments that employed some variant of the habituation-dishabituation and forced-choice preferential looking paradigms. In Experiment 1, three groups--5 1/2, 7 1/2, and 9 months of age--were given a visual choice between rotating rectangular and Ames windows after exposure to a rotating circular form. The two older groups preferred the Ames window. The results of Experiment 2 showed that this preference is not based on structural differences between the two windows. In Experiment 3, familiarization with an Ames window produced a preference for rotary motion while familiarization with a rectangular window produced a preference for oscillatory motion. These results suggest that sensitivity to the illusion emerges around 7 1/2 months of age, an outcome consistent with the emergence, at this time, of sensitivity to pictorial cues to depth.

Child Development↗
PubMed1987

Eye movement as a cue to figure motion in anorthoscopic perception.

When a figure moves behind a narrow aperture in an opaque surface, if it is perceived as a figure, its shape will often appear distorted. Under such anorthoscopic conditions, the speed or direction of the object's motion is ambiguous. However, when the observer simultaneously tracks a moving target, a figure is always perceived, and its precise shape is a function of the speed or direction of tracking. The figure is seen as moving with the speed or in the direction of the target. Thus, it is argued that eye movement serves as a cue to the figure's motion, which, in turn, determines its perceived length or orientation.

Cues↗
PubMed2006

The bar-cross-ellipse illusion: alternating percepts of rigid and nonrigid motion based on contour ownership and trackable feature assignment.

We present a new multistable stimulus generated by continuously rotating an ellipse behind four fixed occluders. Despite the stimulus remaining constant, observers can alternate between one of four percepts: (1) a continuously morphing cross; (2) two independent perpendicular bars oscillating in depth; (3) a rigidly rotating ellipse observed behind the occluders; (4) a fixed cross observed through a continuously rotating, elliptical aperture. Interestingly, the initial percept naive observers tend to see is percept 1, which is the only nonrigid motion percept. This appears to be a violation of the hypothesized 'rigidity heuristic' in which rigid motion percepts tend to be perceived over retinally equivalent nonrigid ones. Here, we describe the relationships between each of the percepts and the assignment of contour ownership and figure/ground segmentation.

Form Perception↗
PubMed1998

The effect of complex motion pattern on speed perception.

We recently reported a new motion illusion where dots in expanding random dot patterns appear to move faster than those in rotation patterns despite having the same physical speed distributions. In the current paper, we compared expansion and rotation motion to translational motion and found that the perceived dot speed in translation patterns was between that of expansion and rotation. We also explored contraction motion and found subjects perceived dots in contracting patterns as moving slightly faster than those in expanding patterns and much faster than those in rotating patterns. Finally, we found that stimulus presentation order in a trial plays an important role in determining the magnitude of the speed illusion--the effect is greater when the subjectively faster stimulus is viewed second (e.g., expansion after rotation). The dependence on stimulus order is greatest when comparing complex motion patterns with large subjective speed differences. This phenomenon is unlikely to be explained in terms of channel fatigue or adaptation.

Humans↗
PubMed2005

The relative importance of spatial versus temporal structure in the perception of biological motion: an event-related potential study.

We investigated how the spatiotemporal structure of animations of biological motion (BM) affects brain activity. We measured event-related potentials (ERPs) during the perception of BM under four conditions: normal spatial and temporal structure; scrambled spatial and normal temporal structure; normal spatial and scrambled temporal structure; and scrambled spatial and temporal structure. As in a previous study, we identified two negative components at both occipitotemporal regions: N210 reflected general motion processing while N280 reflected the processing of BM. We analyzed the averaged ERPs in the 200-300 ms response time window and found that spatial structure had a substantial effect on the magnitude of the averaged response amplitude in both hemispheres. This finding suggests that spatial structure of point-lights elicits a stronger response in the occipitotemporal region than temporal structure for the BM perception.

Adolescent↗
PubMed2007

Perception of human motion.

Humans, being highly social creatures, rely heavily on the ability to perceive what others are doing and to infer from gestures and expressions what others may be intending to do. These perceptual skills are easily mastered by most, but not all, people, in large part because human action readily communicates intentions and feelings. In recent years, remarkable advances have been made in our understanding of the visual, motoric, and affective influences on perception of human action, as well as in the elucidation of the neural concomitants of perception of human action. This article reviews those advances and, where possible, draws links among those findings.

Animals↗
PubMed1996

The visual perception of rigid motion from constant flow fields.

Four experiments investigated observers' judgments of rigidity for different types of optical motion. The depicted structural deformations were of two types: (1) those with nonparallel image trajectories that are detectable from the first-order spatiotemporal relations between pairs of views; and (2) those with parallel image trajectories that can only be detected from higher order relations among three or more views. Patterns were composed of smooth flow fields in Experiments 1 and 3, and of wire frame figures in Experiments 2 and 4. For both types of display, the nonrigidity detectable from the first-order spatiotemporal structure of the motion sequence was much more salient than the deformation detectable only from the higher order spatiotemporal structure. These results indicate that observers' judgments of rigidity are based primarily on a two-view analysis, but that some useful information can be obtained under appropriate circumstances from higher order spatiotemporal relations among three or more views.

Adult↗
PubMed1996

Perception of apparent motion of colored stimuli after commissurotomy.

One subject with complete forebrain commissurotomy (L.B.), another with posterior callosotomy (D.K.), and eight normal controls were presented with successive pairs of red and/or green lights, on either side of the retinal midline and within the left and right visual fields. All of the subjects could discriminate the direction of apparent motion in all three locations, although L.B. was poorer on bilateral than unilateral presentations. Moreover, on bilateral presentations, L.B. was significantly poorer at identifying the color of the first light than the color of the second light. In contrast, D.K., like the control subjects, was equally good at identifying the color of either light. These and other results provide evidence that a subcortical shift in attention enables L.B. to discriminate the direction of apparent motion across the midline. On the other hand, a more robust mechanism involving the middle temporal area of the cortex must be responsible for tracking motion in D.K. and the control subjects. On the basis of these findings, it is suggested that the superior colliculus may contribute to direction sensitivity in the middle temporal area by mediating shifts in spatial attention.

Adult↗
PubMed1981

Adaptive processing of visual motion.

Three studies relating perception of motion to stimulus uncertainty are reported. Generally, detectability declines when the observer is uncertain about the direction in which a target will move, but the visibility loss associated with direction uncertainty can be attenuated if the observer has adequate practice. This attenuation seems to depend upon the observer's ability to switch among directionally selective visual mechanisms in an adaptive fashion. The implications of these findings for models of motion detection are discussed.

Adaptation, Ocular↗
PubMed1990

Eccentricity, contrast, and angular extent as factors in the perception of peripheral apparent motion.

Two experiments were performed to investigate the perception of peripherally presented apparent motion as a function of eccentricity of the stimulus, ambient illumination, sex, stimulus pattern, and angular extent of stimulus presentation. The experimental task for both studies was to judge the direction of apparent motion for a stimulus target lighter than the background and presented on a Braumbach perimeter. The results from Exps. 1 and 2 indicated main effects for subjects and eccentricity. The combined results of Exps. 1 and 2 indicated main effects for eccentricity and angular separation of the apparent motion, however, the interaction between the two was not significant.

Adult↗
PubMed1995

The perception of color from motion.

We introduce and explore a color phenomenon which requires the prior perception of motion to produce a spread of color over a region defined by motion. We call this motion-induced spread of color dynamic color spreading. The perception of dynamic color spreading is yoked to the perception of apparent motion: As the ratings of perceived motion increase, the ratings of color spreading increase. The effect is most pronounced if the region defined by motion is near 1 degree of visual angle. As the luminance contrast between the region defined by motion and the surround changes, perceived saturation of color spreading changes while perceived hue remains roughly constant. Dynamic color spreading is sometimes, but not always, bounded by a subjective contour. We discuss these findings in terms of interactions between color and motion pathways.

Color Perception↗
PubMed1994

Visual perception of intentional motion.

A series of experiments were performed to investigate how motion sequences provide information about the intentional structure of moving figures or actors. Observers had to detect simulations of biologically meaningful motion within a set of moving letters. In the first two experiments a factorial design was used, with type of instruction as a between-subject factor and six movement parameters (number of items, speed and directness of target and distractors, and 'relentlessness' of target movement) as within-subject factor; in the final two experiments, the visibility of the goal towards which the target moved and the use of a tracking movement to distinguish the target were varied. In such displays search time increases with increasing number of stimuli. It was found that (a) the more direct the motion, the more likely it was to be interpreted as intentional; (b) intentional motion was much easier to detect when the target moved faster than the distractors than when it moved more slowly; (c) recognition of intentionality was impaired but not abolished if the goal towards which the target was moving was invisible; and (d) participants did not report intentional movement when the target was distinguished by brightness rather than the manner in which it moved. We argue that the perception of intentionality is strongly related to observers' use of conceptual knowledge, which in turn is activated by particular combinations of features. This supports a process model, in which intentionality is seen as the result of a conceptual integration of objective visual features.

Animals↗
PubMed2002

Isotropic integration of binocular disparity and relative motion in the perception of three-dimensional shape.

Richards (1985) showed that veridical three-dimensional shape may be recovered from the integration of binocular disparity and retinal motion information, but proposed that this integration may only occur for horizontal retinal motion. Psychophysical evidence supporting the combination of stereo and motion information is limited to the case of horizontal motion (Johnston et al., 1994), and has been criticised on the grounds of potential object boundary cues to shape present in the stimuli. We investigated whether veridical shape can be recovered under more general conditions. Observers viewed cylinders that were defined by binocular disparity, two-frame motion or a combination of disparity and motion, presented at simulated distances of 30 cm, 90 cm or 150 cm. Horizontally and vertically oriented cylinders were rotated about vertical and horizontal axes. When rotation was about the cylinder's own axis, no boundary cues to shape were introduced. Settings were biased for the disparity and two-frame motion stimuli, while more veridical shape judgements were made under all conditions for combined cue stimuli. These results demonstrate that the improved perception of three-dimensional shape in these stimuli is not a consequence of the presence of object boundary cues, and that the combination of disparity and motion is not restricted to horizontal image motion.

Cues↗
PubMedDate not supplied

Segregation of pathways leading from area V2 to areas V4 and V5 of macaque monkey visual cortex.

V5 and V4 are areas of macaque monkey prestriate visual cortex that are specialized for involvement in different aspects of visual perception, namely motion for V5 (refs 1-4) and colour vision, with other possible functions, for V4 (refs 2, 5-9). Thus, it is unlikely that they should be fed the same information for further processing, yet both receive a strong input from patches of the upper layers of V2 (refs 10, 11), the area immediately adjoining the primary visual cortex, V1. V2, however, seems to comprise functionally distinct subregions, which can be revealed by staining the tissue for the mitochondrial enzyme cytochrome oxidase. Here we report that V4 and V5 are connected with separate cytochrome oxidase-defined subregions of V2, suggesting that cortical pathways dealing with motion and colour perception are segregated in their passage through V2, and reinforcing evidence for functional specialization in the visual cortex.

Animals↗
PubMed1990

Image statistics and the perception of apparent motion.

The short- and long-range apparent motion processes are discussed in terms of the statistical properties of images. It is argued that the short-range process, exemplified by the random-dot kinematogram, is primarily sensitive to the dipole statistics, whereas the long-range process, exemplified by illusory occlusion, is treated by the visual system primarily in terms of the tripole and higher statistical correlation functions. The studies incorporate the balanced dot, which is a unique stimulus element that permits high pass filtering while preserving detailed positional information. Low spatial frequencies are shown to be critical for texture segregation in random-dot kinematograms, independent of the grain size or number density of texture elements. Illusory path perception in the long-range process is shown not to require low spatial frequencies, but is sensitive rather to global temporal phase coherency. These results are interpreted in terms of the respective roles of the power and phase spectra in perceptual organization. The construction of balanced dots is discussed in detail.

Attention↗
PubMed2002

Motion illusions as optimal percepts.

The pattern of local image velocities on the retina encodes important environmental information. Although humans are generally able to extract this information, they can easily be deceived into seeing incorrect velocities. We show that these 'illusions' arise naturally in a system that attempts to estimate local image velocity. We formulated a model of visual motion perception using standard estimation theory, under the assumptions that (i) there is noise in the initial measurements and (ii) slower motions are more likely to occur than faster ones. We found that specific instantiation of such a velocity estimator can account for a wide variety of psychophysical phenomena.

Contrast Sensitivity↗
PubMed2005

Mechanisms of face perception in humans: a magneto- and electro-encephalographic study.

We have been studying the underlying mechanisms of face perception in humans using magneto- (MEG) and electro-encephalography (EEG) including (1) perception by viewing the static face, (2) differences in perception by viewing the eyes and whole face, (3) the face inversion effect, (4) the effect of gaze direction, (5) perception of eye motion, (6) perception of mouth motion, and (7) the interaction between auditory and visual stimuli related to the vowel sounds. In this review article, we mainly summarize our results obtained on 3, 5, and 6 above. With the presentation of both upright and inverted unfamiliar faces, the inferior temporal cortex (IT) centered on the fusiform gyrus, and the lateral temporal cortex (LT) near the superior temporal sulcus were activated simultaneously, but independently, between 140 and 200 ms post-stimulus. The right hemisphere IT and LT were both active in all subjects, and those in the left hemisphere in half of the subjects. Latencies with inverted faces relative to those with upright faces were longer in the right hemisphere, and shorter in the left hemisphere. Since the activated regions under upright and those under inverted face stimuli did not show a significant difference, we consider that differences in processing upright versus inverted faces are attributable to temporal processing differences rather than to processing of information by different brain regions. When viewing the motion of the mouth and eyes, a large clear MEG component, 1M (mean peak latency of approximately 160 ms), was elicited to both mouth and eye movement, and was generated mainly in the occipito-temporal border, at human MT/V5. The 1M to mouth movement and the 1M to eye movement showed no significant difference in amplitude or generator location. Therefore, our results indicate that human MT/V5 is active in the perception of both mouth and eye motion, and that the perception of movement of facial parts is probably processed similarly.

Adult↗
PubMed2001

Mental imagery of visual motion modifies the perception of roll-vection stimulation.

When viewing a wide-angle visual display, which rotates in the frontoparallel plane around the line of sight, observers experience an illusory shift of the direction of gravity; this shift leads to an apparent tilt of the body and displaces allocentric space coordinates. In this study, subjects adjusted an indicator to the apparent horizontal while viewing a rotating display. To determine whether top down processes could affect the illusion, the subjects were asked to visualize a rotating configuration of dots onto a blank central portion of the moving visual field. Visualizing dots and actually viewing the dots deflected the spatial judgment in very similar ways. These results demonstrate that top down processing can affect allocentric space coordinates.

Adolescent↗