Search PubMed⌕ Search

Biomedical subjects

I E Gordon

Publications and source records attributed to I E Gordon.

18 recordsLinked to original sources
PubMed1993

Occlusion and the distortion of alignment in three-dimensional space.

When observers are asked to align two rectangular stimuli oriented at 45 degrees to the visual axis there is a slight tendency to set the more distant stimulus closer to the eye than its true coplanar position. However, when a large rectangular surface is interpolated between the two oblique stimuli and the observer, errors of alignment become relatively much larger. The displacement caused by the interpolated stimulus occurs both when the display is viewed monocularly and when it is viewed binocularly. Reducing the obliquity of the rectangles results in smaller judgment errors and increasing obliquity increases errors; this is true with and without occlusion. The addition of texture elements to the surfaces of the rectangles reduces judgment errors significantly, but only under conditions of occlusion. It is possible that misalignments recorded for three-dimensional displays have something in common with the two-dimensional Poggendorff illusion.

Adult↗
PubMed1993

A Müller-Lyer-type illusion of egocentric distance with 3D convex and concave objects.

An illusion of egocentric distance with concave and convex objects at a distance of 135 cm is reported. When the centre of a concave object was viewed with both eyes its surface appeared nearer than the centre of the surface of a convex object at the same distance. The distortion was about two per cent of the viewing distance with right-angle objects and about five per cent with hemicylindrical objects. The distortion was slightly reduced when size cues for distance were attached to the surfaces of the objects, absent with monocular viewing, greater with convex than with concave objects, and occurred with the generally convex surface of a model human face. Possible explanations of the findings are discussed.

Defense Mechanisms↗
PubMed1990

Perceived causality occurs with stroboscopic movement of one or both stimulus elements.

It was shown by magnitude estimation that the perception of causality first described by Michotte (1946/1963) also occurs consistently and strongly with stroboscopic, ie apparent or phi, movement. This is so when the 'causal' movement is stroboscopic and the 'caused' movement real, when these movements are reversed, and when both movements are stroboscopic. The effect is not due to prior experience with Michotte-type displays.

Adult↗
PubMed1978

A possible explanation as to why the newly sighted commonly perform well on pseudoisochromatic colour vision tests.

Patients whose vision has been restored after long periods of blindness commonly experience difficulty in perceiving. Parodoxically, such patients often perform well on pseudoisochromatic colour-vision tests. A well-known example is Gregory and Wallace's subject, S.B. who performance on the Ishihara test was perfect. It is suggested that restoration of vision may be associated with relatively poor visual acuity and that this, by filtering higher spatial frequencies, enhances the legibility of pseudoisochromatic test patterns. Two experiments confirm that the Ishihara plates are more legible when seen as defocused images.

Blindness↗
PubMed1975

Electroretinographically determined spectral sensitivity in the tawny owl (Strix aluco).

The electroretinographic (ERG) responses to single light flashes and to flickering lights were obtained in the tawny owl (Strix aluco). The waveform of the single-flash responses indicated that the owl possesses a duplex retina. Spectral sensitivity was determined with light flickering at a 6 and 25 Hz. The sensitivity curve obtained from the 6-Hz responses has a broad maximum between 500 and 525 nm. The 25-Hz sensitivity curve is narrow with a peak at about 600 nm. The sensitivity curves are compared with behaviorally measured sensitivity curves of the pigeon. A close agreement is found between 25-Hz curve and the pigeon red modulator.

Animals↗