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Biomedical subjects

N J Wade

Publications and source records attributed to N J Wade.

At least 73 records · Page 4Linked to original sources
PubMed1978

Op art and visual perception.

An attempt is made to list the visual phenomena exploited in op art. These include moire frinlude moiré fringes, afterimages, Hermann grid effects, Gestalt grouping principles, blurring and movement due to astigmatic fluctuations in accommodation, scintillation and streaming possibly due to eye movements, and visual persistence. The historical origins of these phenomena are also noted.

Afterimage↗
PubMed1978

Sir Charles Bell on visual direction.

Helmholtz is usually credited with demonstrating the relationship between the perception of visual direction and eye muscle activity: he said that directional judgements resulted from the effort of will involved in altering the position of the eyes. However, Bell reached the same conclusion many years earlier, primarily on the basis of experiments with afterimages: an afterimage appeared to move with voluntary movement of the eye, but it appeared stationary when the eye was moved passively.

Afterimage↗
PubMed1977

Distortions and disappearances of geometrical patterns.

Prolonged observation of a stationary grating has a number of perceptual consequences. Initially the lines appear well-resolved and straight. The lines then take on a wavy and oscillating appearance, which is followed by scintillation of the pattern. The scintillations are often accompanied by cloudy disappearances of the grating. A streaming or scintillating aftereffect is visible subsequently, upon viewing a homogeneous surface. The literature concerning these effects is reviewed and several experiments are reported which examined the apparent waviness and scintillating disappearances. The basis for the apparent waviness remains unresolved. It is suggested that the scintillations are produced by small involuntary eye movements over the contours and that the associated disappearances might be due to binocular rivalry.

Eye Movements↗
PubMed1976

On interocular transfer of the movement aftereffect in indivuals with and without normal binocular vision.

The duration of the movement aftereffect was measured in twenty-four normally binocular subjects and in eighteen subjects who lacked steropsis as a consequence of childhood strabismus. Aftereffects were generated monocularly and binocularly, and compared to those which occurred after adaption of one eye and testing with the other. Normal subjects were categorized on two indices of eye dominance, which involved sighting and rivalry tests. The monocular-aftereffect durations were slightly longer when the dominant eye was use, and interocular transfer from the dominant eye to the nondominant eye was greater than the transfer in the reverse direction; however, these differences were not statistically significant. The results from the strabismic subjects suggested that they fell into two distinct groups: one group (seven of the eighteen subjects) experienced no interocular transfer in either direction; the group did yield some interocular transfer, and it was generally greater after adaptation of the dominant eye and testing the nondominant eye than in the reverse direction. Six of the seven subjects who failed to show any transfer still had misalignment of the visual axes, but this was not the case in any of the subjects exhibiting transfer.

Figural Aftereffect↗
PubMed1975

Monocular and binocular rivalry between contours.

The temporal characteristics of binocular and monocular rivalry between orthogonal gratings of the same or complementary colours were investigated. Rivalry was measured in terms of the dominance of either grating or the visibility of composites comprised of parts of both gratings. The total duration for which either grating was dominant was significantly longer in binocular rivalry between gratings of complementary colours. A comparison of binocular and monocular rivalry indicated considerable phenomenal differences between them. Dominance in binocular rivalry corresponds to the visibility of one grating alone; this occurs rarely in monocular rivalry, which is characterized by fluctuations in the distinctiveness of the gratings. The changes in distinctiveness are influenced by colour in a similar manner to that in binocular rivalry, and the frequencies of fluctuations are higher for gratings of complementary colours.

Color Perception↗