Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Motion Perception”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,585 records · Page 88Linked to original sources
PubMed1999

Visual measurement of relative distances between three collinear dots rotating in a slanted plane.

Displays consisted of orthographic and perspective projections of three collinear dots rotating rigidly around a fixed centre in a plane slanted 45 degrees in depth. Observers were asked to decide whether the middle of the three dots was exactly centred in 3-D space between the other two dots. The visible rotation segments were 120 degrees, 160 degrees, or 200 degrees and the displacements were 2%, 4%, or 6%. Our untrained observers performed more poorly overall than well-practised observers tested earlier by Lappin and Fuqua (1983 Science 221 480-482). Results of additional manipulations suggested that 2-D image properties played a more important role than acknowledged by Lappin and Fuqua. First, displacement size and the position of the rotation centre produced nonlinear effects. Second, the direction of displacement affected performance. Third, projection type and display type (static snapshots versus elliptic traces) were involved in complex interactions. Clearly, performance was affected by 2-D image properties that should be irrelevant to the calculation of 3-D projective invariants.

Cues↗
PubMed2002

Perceived internal depth in rotating and translating objects.

Previous research has indicated that observers use differences between velocities and ratios of velocities to judge the depth within a moving object, although depth cannot in general be determined from these quantities. In four experiments we examined the relative effects of velocity difference and velocity ratio on judged depth within a transparent object that was rotating about a vertical axis and translating horizontally, examined the effects of the velocity difference for pure rotations and pure translations, and examined the effect of the velocity difference for objects that varied in simulated internal depth. Both the velocity difference and the velocity ratio affected judged depth, with difference having the larger effect. The effect of velocity difference was greater for pure rotations than for pure translations. Simulated depth did not affect judged depth unless there was a corresponding change in the projected width of the object. Observers appear to use the velocity difference, the velocity ratio, and the projected width of the object heuristically to judge internal object depth, rather than using image information from which relative depth could potentially be recovered.

Cues↗
PubMed2005

Visual representations of dynamic actions from static pictures.

We investigated how subjects used their knowledge of biomechanical constraints when judging whether different items were in balance or in the process of falling, as a function of their angle of slant. In the first experiment, the stimuli were pictures of postures of a human body, of a wooden mannequin, and of a skeleton. The results show that for these 3 items, fall responses appeared for a smaller slant angle for a backward slant than for a forward one. This difference may reflect the influence of biomechanical constraints. To verify whether the asymmetry of the responses to the mannequin and the skeleton was genuine or due to some semantic context effect, a second experiment was run with only pictures of a wooden mannequin. The same asymmetry was observed. In a third experiment, falling judgments were obtained for pictures of a human body and of a structurally comparable artifactual object. The asymmetry of the fall responses appeared only for the human body.

Biomechanical Phenomena↗
PubMed2006

Active steering along corrugated surfaces.

A study is reported of the effect of dynamic occlusion that arises during locomotion over corrugated surfaces and its facilitating role on the control of locomotion, especially in cluttered environments. Surfaces varied in degree of corrugation and type of texture. Heading accuracy was assessed by having participants perform an active steering task. Results demonstrated the advantage of texture-mapped image surfaces over discrete element surfaces in the corrugated conditions. Observers appear to exploit accretion and deletion of optical texture at the occluding edge to extract and use information about heading direction for the control of movements in cluttered environments.

Cues↗
PubMed1973

Cats reared in stroboscopic illumination: effects on receptive fields in visual cortex.

Cats were reared in a light-tight box in which the only source of illumination was a 9-musec strobe flash every 2 sec. This allowed them to experience visual form but they did not experience visual movement. Receptive-field properties of single units in area 17 of the visual cortex of cats reared in stroboscopic illumination (strobe-reared) were compared with properties of units in area 17 of normally reared cats. In strobe-reared cats both direction selectivity and orientation selectivity were greatly reduced relative to normally reared cats, and some units in the strobe-reared cats responded only to strobe flashes.

Animals↗
PubMed1980

Gibson's invariance hypothesis and the Ames oscillatory effect.

Previous explanations of the Ames oscillatory effect are evaluated by means of a functional-evolutionary theory of perception. Use of stored interpretations, static elements, and other explanatory ideas are rejected in favor of adaptive response to ambiguity as the essential factor for the effect. It is emphasized that Ss report perception of rotation, oscillation, reversal, and flapping, which are all correlates of horizontal contraction and expansion of the retinal image, when viewing rotating objects. The provision of all possible correlates of the transforming array is described as supportive of a functional-evolutionary approach, and Gibson's theory of perception.

Animals↗
PubMed1977

Stereomovement from interocular delay in dynamic visual noise: a random spatial disparity hypothesis.

This paper reports a series of tests of the assumptions entailed in the random spatial disparity hypothesis (Tyler, 1974) of the stereophenomenon that occurs on viewing dynamic visual noise with an interocular delay. The results support the hypothesis in opposition to 2 alternative hypotheses. A new stereophenomenon is reported in which reversed steromovement is perceived when viewing dynamic visual noise that has both an interocular delay and complementary contrast between the 2 eyes. Only the random spatial disparity hypothesis appears to account for this reverse stereophenomenon.

Depth Perception↗
PubMed1997

Accommodation to stationary and moving targets.

PURPOSE: To test the hypothesis that the contrast of spectral components of the retinal image specifies ocular focus and controls reflex accommodation. METHODS: Eight subjects viewed a stationary target at 0, 2.5, and 5 D in a Badal optometer, with longitudinal chromatic aberration (LCA) normal and reversed and in monochromatic (550 nm) light. Accommodation was monitored continuously during 40-s trials. Subjects also viewed the grating target as it moved sinusoidally (1.5 to 2.5 D) at 0.2 Hz under the same three conditions. RESULTS: Subjects accommodated relatively accurately at all distances in the normal condition; three subjects had difficulty accommodating in monochromatic light at 5 or 0 D, and seven subjects could not maintain focus with LCA reversed. The accommodative response differed significantly in the three chromatic conditions both for stationary and moving targets. CONCLUSIONS: Relative contrast of long-, middle-, and short-wavelength components of the retinal image specifies ocular focus and drives reflex accommodation.

Accommodation, Ocular↗
PubMed1973

Evidence for the existence of neural mechanisms selectively sensitive to the direction of movement in space.

1. Visual sensitivity to movement in depth was measured as a function of the relative distances through which the left and right retinal images moved. This relative distance (left:right ratio) provides a sensitive cue to the direction along which a target moves in three-dimensional space.2. Gazing at a target which moved along a fixed direction in space produced a gross reduction of visual sensitivity to movements in depth along that direction. For other directions of movement, visual sensitivity was not affected.3. Sensitivity to depth movement rapidly rose almost to the preadaptation level within the first 20-60 sec after removing the adapting target, but recovery was not complete until 100-300 min had elapsed.4. Any adapting target whose left:right ratio fell within a definite range gave similar reductions of visual sensitivity to movements in depth. There were five such ranges.5. The effects of adapting to movement in depth suggest that eight mechanisms underlie depth perception. These mechanisms are ;tuned' to the direction of movement in three-dimensional space. Four mechanisms are wholly concerned with movements along directions very close to the line which cuts midway between the eyes, and do not respond to movements whose direction departs by more than 1.5 degrees from the preferred direction.6. Neural mechanisms ;tuned' to different left:right ratios could provide a physiological basis for sensing the direction in which an object moves in three-dimensional space.

Adaptation, Ocular↗
PubMed1999

Acoustic pursuit of invisible moving targets by cats.

Head movements evoked by an invisible acoustic target were used as a metric to analyze localization of moving sources of sound in naive cats. The target was presented in the lateral sound field and moved along an arc at constant angular speeds. Head-movement trajectories were characterized by a large-magnitude orienting component that undershot the target, and a tracking component elicited by the target during acoustic pursuit. The tracking component was characterized by a succession of stepwise head movements that maintained a relatively close alignment of the median plane of the head with the moving acoustic target.

Animals↗