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Results for “Depth Perception”

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PubMed1975

The role of figure orientation and apparent depth in the perception of the horizontal-vertical illusion.

An experiment was performed which examined the role of figural orientation directly, and the role of an inappropriately invoked size-constancy mechanism indirectly, in the actuation and magnitude of the horizontal-vertical illusion. When the vertical line of the stimulus figure was aligned above the horizontal line, the illusory effect was significant and positive; in contrast, when the vertical line was located below the horizontal line, the illusion was negative. Under the assumption that a vertical line can appear as a foreshortened line in depth, these findings support an explanation based on the operation of a misapplied size-constancy mechanism.

Depth Perception↗
PubMed1999

Stereoscopic depth but not shape perception from second-order stimuli.

Depth can be seen using either linear (first-order) or non-linear (second-order) stereo micropatterns when, in the latter, contrast envelopes contain the disparity information. We examined whether a second-order mechanism can contribute to the perception of 3-D surface shape. Using a variety of different stimulus types, we show that for each, shape is easy to see with linear stimuli. Over a wide range of parameters however, none of our observers perceived shape, however faintly, from the non-linear stimuli. To explore why these elements failed, we simplified our stimulus to a step-edge in depth and measured performance while varying the number of elements. We show how performance declined when more than two non-linear elements were used. We discuss reasons for the limitation found for non-matching elements, including a dissociation for stereopsis between seeing surface shape and depth.

Contrast Sensitivity↗
PubMed1988

Segregation of form, color, movement, and depth: anatomy, physiology, and perception.

Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement--functions that might be difficult to deduce from single-cell response properties.

Animals↗
PubMed2006

The contribution of monocular depth cues to scene perception by pigeons.

The contributions of different monocular depth cues to performance of a scene perception task were investigated in 4 pigeons. They discriminated the sequential depth ordering of three geometric objects in computer-rendered scenes. The orderings of these objects were specified by the combined presence or absence of the pictorial cues of relative density, occlusion, and relative size. In Phase 1, the pigeons learned the task as a direct function of the number of cues present. The three monocular cues contributed equally to the discrimination. Phase 2 established that differential shading on the objects provided an additional discriminative cue. These results suggest that the pigeon visual system is sensitive to many of the same monocular depth cues that are known to be used by humans. The theoretical implications for a comparative psychology of picture processing are considered.

Animals↗
PubMed1997

Misperceptions of angular velocities influence the perception of rigidity in the kinetic depth effect.

Accuracy in discriminating rigid from nonrigid motion was investigated for orthographic projections of three-dimension rotating objects. In 3 experiments the hypothesis that magnitudes of angular velocity are misperceived in the kinetic depth effect was tested, and in 4 other experiments the hypothesis that misperceiving angular velocities leads to misperceiving rigidity was tested. The principal findings were (a) the magnitude of perceived angular velocity is derived heuristically as a function of a property of the first-order optic flow called deformation and (b) perceptual performance in discriminating rigid from nonrigid motion is accurate in cases when the variability of the deformations of the individual triplets of points of the stimulus displays favors this interpretation and not accurate in other cases.

Depth Perception↗
PubMed2003

Disorders of motion and depth.

Damage to the human homologue of area MT produces a motion perception deficit similar to that found in the monkey with MT lesions. Even temporary disruption of MT processing with transcranial magnetic stimulation can produce a temporary akinetopsia [127]. Motion perception deficits, however, also are found with a variety of subcortical lesions and other neurologic disorders that can best be described as causing a disconnection within the motion processing stream. The precise role of these subcortical structures, such as the cerebellum, remains to be determined. Simple motion perception, moreover, is only a part of MT function. It undoubtedly has an important role in the perception of depth from motion and stereopsis [112]. Psychophysical studies using aftereffects in normal observers suggest a link between stereo mechanisms and the perception of depth from motion [9-11]. There is even a simple correlation between stereo acuity and the perception of depth from motion [128]. Future studies of patients with cortical lesions will take a closer look at depth perception in association with motion perception and should provide a better understanding of how motion and depth are processed together.

Alzheimer Disease↗
PubMed1994

Ambiguous pictorial depth cues and perceptions of nonrigid motion in the three-loop figure.

The three-loop figure is a two-dimensional (2-D) pattern that generates (mis)perceptions of nonrigid three-dimensional (3-D) structure when rotated about its centre. Such observations have been described as counterexamples to the principle whereby a moving object is presumed to be rigid, provided that a rigid interpretation is possible (ie the 'rigidity constraint'). In the present investigation we demonstrated that stationary three-loop figures exhibit many of the classic properties of multistable/ambiguous figures, with any one of several possible 3-D configurations being reported at any one instant. Further investigation revealed that perceived nonrigidity during rotation was markedly reduced (and rigidity enhanced) when the figure was modified with static pictorial depth cues (eg shading, interposition). These cues had no effect on the overall proportion of time that observers reported 3-D organisations in stationary versions of the figure, but significantly reduced the frequency of perceptual reorganisation, and increased the duration for reporting a particular organisation. Since each of the perceived 3-D structures in a stationary ambiguous 2-D figure has a unique kinetic counterpart (ie rigid transformation), we attribute the nonrigid structure perceived when the figure rotates to the integration of these otherwise inconsistent kinetic components; and have further illustrated this with modified versions of a Penrose impossible triangle. Under kinetic versions of the classical size/distance invariance hypothesis, the rigidity constraint may be considered to represent a special instance of size/shape constancy, in which case counterexamples involving (mis)perceptions of nonrigid structure are comparable to other well-known exceptions to such principles of minimum object change (eg classical illusions).

Cues↗
PubMed2005

Thresholds for perception of ripple depth in the passband of a low-pass filter.

Filters are often used in research related to speech and tone perception. Idealized filters with flat pass-bands, flat stop-bands, and infinitely steep rolloff are impossible to implement, thus practical filters often have a frequency response curve that has a certain degree of ripple, and always have finite rolloff. Despite this, there is a dearth of literature concerning the sensitivity of the ear to such artifacts. In the current study we examined the threshold of sensitivity to ripple depth in the pass-band of a digital low pass finite impulse response (FIR) filter. FIR filters are often used due to their lack of phase distortion, and due to the fact that their ripple depth can be closely controlled. Using an adaptive threshold detection paradigm, we found the threshold of noticeable ripple depth to be 2.7 dB (SD = 1.45) for filtered noise, and 4.89 dB (SD = 2.09) for a filtered chirp signal. This is significantly larger than the difference limen in intensity (DLI) for noise or pure tones. Notably, the threshold for filtered noise is significantly lower and more uniform across subjects, compared to the threshold for a filtered chirp signal. We conclude that these issues must be addressed when the necessity for filtering arises, though they cannot be considered independently of the signals themselves.

Acoustic Stimulation↗
PubMed1989

Perception of slant-in-depth is automatic.

Two experiments assessed perception of the slant-in-depth of static irregularly contoured shapes when attention was withdrawn from processing slant-in-depth. The experiments showed that when the memory load of the experimental task is minimal, discrimination of slant-in-depth is evidenced even when attention has not been directed to slant discrimination. The findings are brought to bear on a model of perceiving shape-at-a-slant (Epstein & Lovitts, 1985) that partitions the components of the process into automatic and attention-demanding operations.

Adult↗
PubMed1991

Purely chromatic perception of motion in depth: two eyes as sensitive as one.

Motion hyperacuity (phase) thresholds were measured for both lateral and stereoscopic oscillatory motion in both luminance and equiluminant red/green gratings of 2 cycles per degree. Thresholds for lateral chromatic motion did not exhibit the inhibitory fall-off at low temporal frequencies that was found for luminance motion. Phase thresholds for purely chromatic motion were substantially higher than those for luminance gratings, in proportion to the ratio of cone signal modulation, but they could be predicted from the corresponding contrast sensitivities for both types of stimulus. Stereomovement thresholds in luminance gratings showed the stereomovement suppression effect relative to monocular motion sensitivity previously reported for line stimuli, but purely chromatic gratings did not. Together with the lack of an inhibitory fall-off, these results imply that chromatic and luminance motion are processed by different neural pathways, and that the chrominance pathway is capable of supporting a strong percept of stereoscopic motion from purely chromatic gratings.

Attention↗