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At least 19 recordsLinked to original sources
PubMed1992

Individual differences in afterimage persistence: relationships to hypnotic susceptibility and visuospatial skills.

To investigate the moderating role of individual differences in hypnotic susceptibility and visuospatial skills on afterimage persistence, we presented a codable (cross) flash of light to 40 men and 46 women who had been dark adapted for 20 min. In an unrelated classroom setting, subjects had previously been given two standardized scales of hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility, Shor & Orne, 1962; Group Stanford Hypnotic Susceptibility Scale, Form C, Crawford & Allen, 1982) and the Mental Rotations Test (Vandenberg & Kuse, 1978). The first afterimage interval and the afterimage duration correlated significantly with hypnotic responsiveness, supporting Wallace (1979), but did not show the anticipated relationships with mental rotation visuospatial skills. Individuals in the high hypnotizable group had (a) significantly longer afterimage intervals between its first appearance and first disappearance than did those in medium or low groups, as well as (b) significantly longer afterimages between the first appearance and the final disappearance than did those in low groups, but those in medium groups did not differ significantly from the other groups. Discriminant analysis using the afterimage persistence measures classified correctly 65.2% of high hypnotizables, 37.5% of medium hypnotizables, and 54.8% of low hypnotizables. Hypothesized cognitive skills that assist in the maintenance of afterimages and underlie hypnotic susceptibility include abilities to maintain focused attention and resist distractions over time and to maintain vivid visual images.

Adult↗
PubMed1977

Spatial-frequency adaptation and afterimages.

The contribution of afterimages to spatial-frequence adaptation was studied by comparing a number of different fixation paradigms designed to maximize of minimize afterimages. While it is clear that adaptation is not an afterimage artifact, nevertheless afterimages are produced at low spatial frequencies and can considerably distort the results of adaptation experiments unless steps are taken to eliminate them.

Adaptation, Ocular↗
PubMed1979

Sex differences in the perception of autokinetic movement of an afterimage.

The effects of stimulus color and gender upon the perception of an afterimage were examined. The Ss were 32 male and 32 female college undergraduate volunteers. Eight Ss of each gender viewed a pinpoint flash of light through one of four filters: blue-green (Wratten 44A), red (Wratten 92), yellow (Wratten 9), or a neutral (Wratten 96) filter. Each S was given three trials, and on each trial, the duration of the afterimage was recorded, along with changes of direction, and changes in perceived color. Males reported significantly (p less than .05) more autokinetic movement of the afterimage. The color of the stimulus affected afterimage duration differentially for the two genders (p less than .05), and there was also a significant interaction (p less than .02) of gender with filter color for the total number of color changes reported. Thus, it is likely that both outflow monitoring and error signal variables in the autokinetic effect may be affected by gender, and the two sexes may also have different retinal and/or central processing of visual information.

Afterimage↗
PubMed1978

Complementary afterimages and the unequal adapting effects of steady and flickering light.

Prolonged exposure to flickering chromatic light of moderate intensity produce a much weaker complementary afterimage than that produced by exposure to stead light of the same average intesity. This difference in adapting effectiveness was investigated by determining theretinal illuminance of the study adapting field required to produce an afterimage equal to that produced by the flickering adapting field. In a variety of conditions, the greater effectiveness of the steady adapting field was confirmed; in several instances a steady field having an average retinal illuminance of only 0.05 times that of the flickering field gave rise to an equally saturated afterimage. The results are taken as evidence that complementary afterimages produced by extended moderate intensity exposure are primarily a consequence of neural adaption.

Adaptation, Ocular↗
PubMed1975

Temporal and spatial aftereffects of a border on an afterimage and a possible laterality difference.

Five subjects were asked to report the brightness and duration of afterimages formed in a region where a border had previously been exposed. The temporal and spatial aftereffects of the border on the formation of the afterimage varied with the duration of the border and these aftereffects were within the area predicted by a photochemical bleaching hypothesis. In addition to these major findings, the experiment yielded some surprising secondary observations. For example, increasing the degree of bleaching or light adaptation made the afterimage brighter if it was on the right side but decreased the brightness if on the left. The difference between afterimages on the right and left sides was discussed in terms of spatial effects of borders and laterality differences.

Adaptation, Ocular↗
PubMed1992

The apparent shape of afterimages in the Ames room.

When observers project afterimages of circular patterns onto a surface slanting away from them the images are reported as being oval in shape. In this paper it is reported that this does not occur when similar afterimages are projected onto the slanting rear wall of an Ames room. Instead of appearing as ovals, the afterimages remain circular. It appears as though the actually-slanted rear wall of the room not only looks as if it is normal to the line of vision, but also that it functions as if it was in such an orientation as far as a projection surface for afterimages is concerned. While these results are consistent with Emmert's law and with traditional accounts of shape and size constancy, they raise once again the age-old issue of whether the 'image on the retina' constitutes an object of perception that can be described in terms of its shape or size.

Adult↗
PubMed1978

Autokinetic movement of an induced afterimage.

Thirty-two female Ss participated in an experiment in which autokinetic movement (AKM) direction change frequency of an induced afterimage was assessed as a function of stimulus afterimage color (yellow or blue-green) and the presence or absence of eye strain. Afterimage color was found not to affect AKM frequency reports. However, eye strain significantly (p less than .002) affected such reports, with the fewest AKM direction changes reported when strain was present. These results were explained in terms of an error signal and noise analysis of AKM.

Afterimage↗
PubMed1979

Initial-image and afterimage discrimination in the human rod and cone systems.

1. The rod-isolation technique of Aguilar & Stiles (1954) was used to obtain scotopic increment-threshold functions in the dark-adapted eye. Increment-threshold functions were obtained for background durations of 50 to 500 msec, but the onset of the background and increment fields was always simultaneous. In all conditions the duration of the increment field was 50 msec. 2. The pattern of results obtained is the same as that reported earlier for the cone system (Geisler, 1978). For background durations greater than that of the increment field, the increment-threshold functions have two distinct branches. It was shown, by measuring action spectra, that both branches reflect the sensitivity of the rod system. 3. When the increment thresholds are plotted as a function of background retinal illuminance, all the lower branches superimpose. This implies that those thresholds are dependent only on the number of background quanta absorbed during presentation of the increment field. On the other hand, when the increment thresholds are plotted as a function of background energy, all the upper branches superimpose, implying that those thresholds are determined by the total number of background quanta absorbed. 4. For the thresholds falling on the lower branches observes reported that the increment field was detected in the initital image of the background and increment fields when they were flashed. For the upper branches, the increment field was detected in a short-term afterimage that appeared after the background was extinguished. The higher the background intensity the longer was the latency until the increment appeared in the afterimage. 5. All of the above findings appear to be consistent with the known properties of the electrical responses of vertebrate photoreceptors. A model based on Penn & Hagins' (1972) model for the photocurrent in rat rods predicts, fairly accurately, the rod and cone increment-threshold results. The parameters estimated by fitting the model support the hypothesis that the short-term rod and cone afterimages are due to the relatively slow decay of internal transmitter, but they suggest that post-receptor mechanisms are responsible for the threshold saturation observed with flashed backgrounds.

Afterimage↗
PubMed1977

Persistence of complementary afterimages as a function of adult age and exposure duration.

The persistence of complementary afterimages was studied in 36 young (X age 18.8 years) and old (X age 62.1 years) male and female subjects. Afterimage persistence was found to be a direct function of exposure duration and to be greater for the older subjects as compared with the younger ones. The interactions between age and duration and between presentation order and duration were also significant. The data extend support for the "stimulus persistence" model to age differences in retinal function.

Adolescent↗
PubMed1976

Conditioning afterimages: a procedure minimizing the extinction effect of normal test trials.

Six subjects were trained on a conditioning schedule of ten trials a day for 25 days: a further 18 CS-US pairings were presented on 4 subsequent days. The tone employed as the CS was put on 30 sec before the presentation of a briefly illuminated visual target (the US) and maintained until terminated by the subject when his afterimages disappeared. This procedure allowed continuous monitoring of the evolution of the conditioned response (conditioned afterimages): directly for CRs with a latency of less than 30 sec which could occur on every training trial before the US was presented; indirectly from the changes in the duration of afterimagery following the presentation of the US. As every trial yielded some evidence about the evolution of the CR, unreinforced test trials were not necessary after every block of training trials so minimizing the extinction effect attributable to the presentation of an unreinforced CS. In the course of the experiment the mean duration of afterimagery increased almost fivefold with one subject showing a tenfold increase. Five of the subjects experienced visual images in response to the tone alone and were judged to be conditioned. The data are discussed in relation to the evolving levels of conditioning identified by Bzhalava (1958, 1965).

Acoustic Stimulation↗
PubMed1992

Optical illusions in clinical dermatology: the Mach band phenomenon and afterimages.

A survey of dermatologists was conducted to determine whether the perceptions of afterimages and Mach bands impacted on clinical dermatology practice. 26.5% (13/49) of respondents indicated that they perceived one or both of these optical illusions. No false-positive potassium hydroxide interpretations of skin scrapings for hyphae were reported due to perceived afterimages, and no skin biopsies were reportedly performed as a result of Mach bands.

Adult↗
PubMed1979

Hypnotic susceptibility and the perception of afterimages and dot stimuli.

Three experiments were conducted to determine the relationship between hypnotic susceptibility level and the susceptibility to several perceptual phenomena. Experiment I required subjects to observe an induced afterimage in a light-proofed environment and to report the frequency of direction and color changes. In addition, subjects reported the persistence of the afterimage. Experiment II involved the observation of a black dot against a white background, with frequency of observed movement being the dependent measure. Experiment III was similar to the second experiment except that the stimulus was encompassed by a frame. In Experiments I and II, subjects judged high in hypnotic susceptibility reported perceiving the strongest effect. This phenomenon was virtually eliminated in the third experiment. These results were interpreted as supporting a process whereby subjects judged high in hypnotic susceptibility are better able to selectively attend to relevant cues in a stimulus array during conditions of perceptual impoverishment.

Attention↗
PubMed1976

Sex differences in visual persistence: experiments on the Ganzfeld and afterimages.

Sex differences were investigated in two experiments on visual persistence: the Ganzfeld and the afterimage. Males were found to hold visual sensation longer than females, particularly in the Ganzfeld where there was little overlap of scores. Variability of experience in the Ganzfeld was also greater for males and they commonly reported 'blank-out' effects while females did not. There was further evidence from both experiments that females are more responsive to the long-wave region of the frequency spectrum.

Adolescent↗
PubMed1978

Retinal mechanisms of visual adaptation and afterimages.

Recent results obtained from recordings of isolated photoreceptor activity and from correlations of this activity with time-dependent changes in the responses of other retinal cells in several vertebrates have made a thorough revision of former theories of visual adaptation necessary. The present paper reviews the current state of research and relates the new discoveries with psychophysical findings in an attempt to explain human light and dark adaptation from the novel starting point. The former conceptions of adaptation have to be replaced with a three-level process consisting of photochemical receptor neural and network adaptation. Several adaptive mechanisms can be discerned at each level. Depending on adaptation conditions, any level of the three can play a dominating role and can also produce afterimages that display the behaviour of the mechanisms working at each level. The total achievement of visual adaptation is an optimized end product of the actions of all the various mechanisms.

Adaptation, Ocular↗