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At least 73 records · Page 4Linked to original sources
PubMed1991

Apparent size as a function of vertical gaze direction: new tests of an old hypothesis.

The hypothesis was tested that the decline of apparent size with elevated gaze results from a latent tendency of the eyes to diverge and thus increased vergence effort. Through the use of a method of category estimation, the decline of apparent size on elevation or depression of gaze was found not to be different between subjects with larger or smaller changes of dark vergence and thus vergence effort. In a 2nd experiment, vergence effort was varied by varying gaze elevation and the angle of convergence. With vergence effort constant, apparent size was dependent on the angle of convergence rather than being constant. It is concluded that apparent size does not depend on vergence effort and that the effect of gaze elevation on apparent size cannot be attributed to its concomitant effect on dark vergence.

Adolescent↗
PubMed1992

Stereokinetic effect and its relation to the kinetic depth effect.

The stereokinetic effect (SKE) has been defined and studied by nested circular patterns rotating on a turntable. Circles must appear not to rotate as they revolve, which in turn results in their appearing to translate relative to one another. A powerful illusion of object depth results even though the individual circles do not undergo an appropriate foreshortening consistent with their apparent changes in slant. It is suggested and tested that the SKE is based on the changing positions between the nested contours despite the absence of any change within each contour, whereas the kinetic depth effect (KDE) entails both kinds of change. It follows that a turntable method of presentation is not necessary, and between-contour transformations can be simulated by computer animation. Displays consisting of simple translations were shown to evoke robust depth impressions as were patterns consisting of contours of varying shapes. Comparisons of the depth, compellingness, and rigidity of matched SKE and KDE displays are reported. The SKE is taken to be paradigmatic for how the visual system perceives depth when observing small object rotations that occur in everyday situations.

Depth Perception↗
PubMed1977

Stereopsis in toads.

Explore the source record for details and available documents.

Accommodation, Ocular↗
PubMed1985

[Measurement of stereoscopic vision in 6-year-old preschool children].

Stereoacuity can be measured accurately in 6-year-old (pre-school age) children using a specially designed test. The values obtained, measured with stereo testers for long-range and close-range vision, do not differ significantly from those obtained in adults. Hence, it appears that the development of binocular vision must be terminated earlier than hitherto assumed. The limiting factor in stereo measurements at this age and with these methods is the degree of maturity of the children's mental and motor capabilities.

Child↗
PubMed1975

Recalibration by pairing: a process of perceptual learning.

When two cues which normally agree in determining perceived depth are experimentally paired so that they designate discrepant values for the depth dimension, an opportunity is created for the recalibration or re-evaluation of the cues. Experiments which show recalibration of the oculomotor cues and recalibration of binocular disparity as a result of pairing these cues with other discrepant cues are reviewed. The locus of change is related to the relative dominance of different cues and the contribution of allocation of attention in determining dominance is discussed. Implications of recalibration by pairing for understanding ontogenetic development are considered. It is suggested that some cues may acquire their effectiveness as a consequence of pairing during development.

Cues↗
PubMed1989

Measuring attention using induced motion.

Attention was measured by means of its effect upon induced motion. Perceived horizontal motion was induced in a vertically moving test spot by the physical horizontal motion of inducing objects. All stimuli were in a frontoparallel plane. The induced motion vectored with the physical motion to produce a clockwise or counterclockwise tilt in the apparent path of motion of the test spot. Either a single inducing object or two inducing objects moving in opposite directions were used. Twelve observers were instructed to attend to or to ignore the single inducing object while fixating the test object and, when the two opposing inducing objects were present, to attend to one inducing object while ignoring the other. Tracking of the test spot was visually monitored. The tilt of the path of apparent motion of the test spot was measured by tactile adjustment of a comparison rod. It was found that the measured tilt was substantially larger when the single inducing object was attended rather than ignored. For the two inducing objects, attending to one while ignoring the other clearly increased the effectiveness of the attended inducing object. The results are analyzed in terms of the distinction between voluntary and involuntary attention. The advantages of measuring attention by its effect on induced motion as compared with the use of a precueing procedure, and a hypothesis regarding the role of attention in modifying perceived spatial characteristics are discussed.

Adult↗
PubMed1990

Wallpaper illusion: cause of disorientation and falls on escalators.

The wallpaper illusion, first described over a century ago, can occur when a person with normal binocular vision views a pattern that is periodic in the horizontal meridian of the visual field. Escalator trends present such a pattern. Evidence is presented favoring the view that disorientation experienced by escalator riders is caused by this illusion. Possibly some of the estimated 60,000 escalator falls occurring in the United States each year are linked to it.

Accidental Falls↗
PubMed1991

The ceiling of the Church of St Ignatius and the perception of concave surfaces.

This research describes two hitherto unobserved phenomena in the frescoes of the seventeenth century architect and painter, Andrea Pozzo, painted on the vaulted ceiling of the central nave of the Church of St Ignatius in Rome. The present research also reports the results of two experimental studies on the problem of the perception of shapes projected on concave surfaces. A quantitative evaluation of the phenomena perceived from various points of observation is made by means of stimuli projected at various angles on a semicylindrical surface. The validity of the assumption of invariance, and in particular of the projective invariant called the cross-ratio, is discussed within the framework of ecological theories on perception.

Architecture↗
PubMed1992

Grouping based on phenomenal similarity of achromatic color.

It is widely acknowledged that a precondition for the perception of the world of objects and events is an early process of organization, and it has generally been assumed that such organization is based on the Gestalt laws of grouping. However, the stage at which such grouping occurs, whether early or late, is an empirical question. It is demonstrated in two experiments that grouping by similarity of neutral color is based not on similarity of absolute luminance at the level of the proximal stimulus, but on phenomenal similarity of lightness resulting from the achievement of lightness constancy. An alternative explanation of such grouping based on the equivalence of luminance ratios between elements and background is ruled out by appropriate control conditions.

Adult↗
PubMed1979

A developmental study of three-dimensional perception in Israeli children.

One hundred thirty-six 5- to 10-year-old Israeli male and female children were given three black and white photographs of a highway, a column of identical tanks, and a row of elephants, and were asked some questions on each one of the photographs in order to elicit responses of three-dimensional perception. The results showed a clear developmental pattern, quite similar to what has been found in other studies. It appears that the procedure used in the present study is an easier and probably more reliable way of assessing perspective responses than the original procedure of Piaget and Inhelder.

Child↗
PubMed1976

Telescopic lenses and driving.

In some states, persons with significantly reduced visual acuity are being licensed to drive while wearing telescopic spectacle lenses (TSL). In order to evaluate possible visual field limitations present with these devices, the peripheral visual fields of a group of normally sighted subjects were measured while they wore TSL. Severely restricted central fields and sizeable ring scotomas were present with all units tested. These result indicate that driving with TSL should be discouraged.

Accidents, Traffic↗
PubMed1984

Horopter shifts due to a magnification change.

Both the equidirection ( nonius ) and the equidistance horopter criteria were used on a group of subjects with and without the application of a 5% overall magnifier before the right eye. For three of six subjects, shifts in the equidirection horopter induced by this afocal lens could not be predicted on the basis of the magnification properties of the lens and the assumption that corresponding points are fixed. Equidistance horopter plots showed reasonably systematic reductions in slope between the predicted and the measured values for all subjects. Irregularities in all data were accounted for by shifts in the vergence angles during the experiment.

Aniseikonia↗