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Biomedical subjects

R H Day

Publications and source records attributed to R H Day.

At least 73 records · Page 4Linked to original sources
PubMed1980

The effect of blurring on intersecting-line illusions.

It was observed by chance that illusions in patterns consisting of criss-crossing lines, such as the Orbison and Hering illusions, are markedly reduced when the patterns are blurred. In the first of two experiments the reduction with blurring was confirmed for four patterns but failed to occur in patterns lacking criss-crossing lines. In the second experiment the reduction was shown to be due mainly to the reduced luminance contrast in blurred patterns, thus confirming earlier findings on the effect of contrast of this group of illusions. Theoretical implications are discussed.

Adolescent↗
PubMed1979

The demonstration of maedi/visna virus in sheep in Great Britain.

A virus indistinguishable from that causing maedi/visna has been isolated from a sheep flock in Great Britain. The virus was identified in cell cultures using immunofluorescent and electron microscopical techniques. The complement fixation test and the agar gel immunodiffusion test were used to assess the proportion of serological reactors within the flock. There has been no evidence of clinical disease in the flock into which foreign imports were introduced in the years prior to 1976.

Animals↗
PubMed1979

The relationship between brightness contrast and illusory contours.

One group of subjects rated differences in brightness and another the clarity of illusory contours for eight figure-ground combinations of the Kanizsa and Ehrenstein patterns made from Munsell papers. For four combinations there was a difference in Munsell value (brightness) between figure and ground and for another four no difference. For the latter the pattern was derived from differences in hue or colour quality. For the combinations with a Munsell value difference the ratings of both brightness difference and contour clarity were high and for those of uniform value both were low. The results are interpreted as supporting the argument that illusory contours derive primarily from contrast-induced differences in brightness and possibly in colour between contiguous, physically uniform regions.

Color Perception↗
PubMed1976

The components of the Poggendorff illusion.

An explanation of the Poggendorff misalignment illusion in terms of three basic components, the horizontal-vertical, longitudinal-transverse and obtuse angle effects, is proposed. It is argued that these effects amy either singly or jointly give rise to an apparent elongation- contraction of the space between the aligned elements with consequent change in apparent oblique direction. Experimental evidence for the involvement of the three components in various combinations and for modification of perceived direction between the transversals is presented. It is shown that the illusion in various forms of the Poggendorff figure can be accounted for by the involvement of one or more of the three components, each of which can be demonstrated independently of the illusion. It is suggested that other classical illusions, including the Müller-Lyer, might also be analysed in terms of basic components.

Humans↗