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At least 793 records · Page 44Linked to original sources
PubMed1975

Identification of tachistoscopically exposed symmetrical and asymmetrical letter arrays.

Six-letter arrays containing symmetrical, e.g., H, M, T, or asymmetrical letters, e.g., J, K, R, were tachistoscopically exposed bilaterally for 100 msec. to 100 college students. Significantly more asymmetrical than symmetrical letters were identified, and significantly more Ss identified more asymmetrical than symmetrical items. This experiment, which incorporated methodological considerations suggested by Harcum (1964) and Bryden (1968), corroborates their findings. Their ideas and other findings were used to account for the data. Asymmetrical letters have more intrinsic left-to-right directionality than symmetrical elements. The rapidly fading after-stimulation of tachistoscopically presented alphabetical material is usually scanned from left to right. Individual array letters might also be scanned in the same direction. Confluence of directionality of letter and scan, which obtains only with asymmetrical letters, might have typically allowed asymmetrical targets to be scanned more rapidly and, consequently, more efficiently than symmetrical displays.

Afterimage↗
PubMed1997

Does local or global orientation determine the McCollough effect?

In this research, the McCollough effect was observed by using an ambiguous test pattern of coarse gratings made out of fine gratings. Coarse gratings meet at right angles to fine gratings. The global features (coarse gratings) in the test pattern became more salient if the test pattern was blurred, and the frequency of the McCollough effect, corresponding to the global orientation of the test pattern, increased with the increase of the extent of blur. The McCollough effects corresponding to the local orientation of the test pattern occurred frequently if the subjects adapted to fine gratings before viewing the test pattern, whereas the McCollough effects corresponding to the global orientation of the test pattern occurred frequently if the subjects adapted to coarse gratings. Our results indicate that the perceptual organization is an important determinant in the McCollough effect.

Adult↗
PubMed1998

Binocular vertical perceptual adaptation in essential infantile esotropia.

This study assessed whether dissociated vertical deviation, corresponding to an occasional elevation of the deviated eye, is accompanied by a binocular vertical perceptual adaptation. Dissociated vertical deviation was elicited by means of neutral filters in 16 patients, 8 who had undergone operations for the disorder of essential infantile esotropia and 8 who had not. Neutral filters elicited dissociation vertical deviation, which was accompanied by binocular vertical perceptual adaptation. This effect was significantly greater for patients who had operations and was enhanced by the filter density. Surgical elimination of inhibitory mechanisms for dissociated vertical deviation in patients with essential infantile esotropia appears to facilitate a loose sensory adaptation, which permits a binocular vertical perceptual adaptation.

Adolescent↗
PubMed1999

Effect of luminance contrast on the motion aftereffect.

The effects of luminance contrast and spatial frequency on the motion aftereffect were investigated. The point of subjective equality for velocity was measured as an index of the motion aftereffect. The largest effect was observed when a low contrast grating (5%) was presented as a test stimulus after adaptation to a high contrast grating (100%) in the low spatial frequency condition (0.8 cycle deg.-1). On the whole, the effect increased with increasing adapting contrast and with decreasing test contrast or spatial frequency. Small effects were observed at high test contrasts. These results were inconsistent with those of Keck, Palella, and Pantle in 1976. Analysis showed that there was no saturation on velocity of the motion aftereffect above 5% of the contrast although Keck, et al. (1976) found that the incremental increases of the effect above 3% adapting contrast were small.

Afterimage↗
PubMed2001

A biochemical analysis of people with chronic fatigue who have Irlen Syndrome: speculation concerning immune system dysfunction.

This study investigated the biological basis of visual processing disabilities in adults with Chronic Fatigue Syndrome. The study involved 61 adults with symptoms of Chronic Fatigue Syndrome who were screened for visual processing problems (Irlen Syndrome) and divided into two groups according to the severity of symptoms of Irlen Syndrome. Significant variations were identified in blood lipids and urine amino and organic acids of the two groups, which may be indicative of activation of the immune system due to some infective agent. It was suggested that metabolic profiling may help the development of more valid diagnostic categories and allow more investigation of immune system dysfunction as a possible causal factor in a range of learning and behaviour disorders.

Adult↗
PubMedDate not supplied

The "marche-en-étoile" revised. The influence of after-images and prism-glasses on starwalks.

An analysis of the role that casual after-images play in starwalk (marche-en-étoile) tests, shows that these can be turned from unreliable into reliable tests. The vestibular function test described in this article is as follows: (a) the individual walks with open eyes to a point of reference 5 m distant. On arrival, he closes his eyes and walks backward and forward according to the marche-en-étoile procedure. (b) Same procedure as (a), but now the orientation point is replaced by a light source that is switched off when the patient reaches it. (c) Same procedure as (b), but now the patient is wearing prism-glasses. It turns out, the deviations in the starwalk are caused mainly by drifting of the after-image. This drift is based on an oculogyral illusion, and it appears that it can be influenced by wearing prism-glasses. These investigations reveal the existence of hitherto too little known interactions between the vestibular and the visual system.

Afterimage↗