PubMed · 4561840
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
W J Lovegrove, R Over, J Broerse. 1972-08-11. Colour selectivity in motion after-effect.. https://doi.org/10.1038/238334a0
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
When a participant moves a hand-held target in complete darkness after an afterimage of that target has been obtained, an illusory increase (with movements away from the participant) or decrease (with movements towards the participant) in the apparent size of the afterimage is reported (the Taylor illusion, reported first in Taylor, J Exp Psychol 29: 1941). Unlike typical Emmert's Law demonstrations, the Taylor illusion shows that a motor-related signal can be used to specify distance for the computation of real size. A study by Carey and Allan (Exp Brain Res 110: 1996) found that the Taylor illusion did not occur in a condition where an afterimage of one hand was obtained while the other hand performed a movement away from the participant from directly behind the first. It was proposed that, for the illusion to manifest itself, proprioceptive and visual information must be in strict "register" when the afterimage is obtained. To evaluate this hypothesis, 14 participants performed "towards" and "away" movements after obtaining afterimages of hand-held cards. Participants wore either plain lenses or prism lenses during the trials, the latter of which displaced visual stimuli 10 degrees to the left. No significant difference was found between the two lens conditions in terms of the effect on the perception of the Taylor illusion. It was concluded that the illusory size distortions may depend on register of visual and proprioceptive position in terms of depth, rather than in the picture plane. Several suggestions for future studies of the Taylor illusion are proposed, and limitations of size judgements of afterimages are outlined.
Small eye movements are necessary for maintained visibility of the static scene, but at the same time they randomly oscillate the retinal image, so the visual system must compensate for such motions to yield the stable visual world. According to the theory of visual stabilization based on retinal motion signals, objects are perceived to move only if their retinal images make spatially differential motions with respect to some baseline movement probably due to eye movements. Motion illusions favoring this theory are demonstrated, and psychophysical as well as brain-imaging studies on the illusions are reviewed. It is argued that perceptual stability is established through interactions between motion-energy detection at an early stage and spatial differentiation of motion at a later stage. As such, image oscillations originating in fixational eye movements go unnoticed perceptually, and it is also shown that image oscillations are, though unnoticed, working as a limiting factor of motion detection. Finally, the functional importance of non-differential, global motion signals are discussed in relation to visual stability during large-scale eye movements as well as heading estimation.
The glare effect is an illusion in which a region appears self-luminous when flanked by gradients that decrease in luminance with distance from the region (Zavagno, 1999 Perception 28 835-838). This region also appears brighter than a surface of the same luminance. We investigated, using the paradigm of afterimages, whether a low-level mechanism at the level of the retina or LGN could account for this apparent brighter sensation. We first replicated the result from the literature that brighter and longer-lasting physical stimuli generate longer-lasting afterimages. We then compared the glare-effect stimuli with their counterpart controls, and found that the glare-effect stimuli did not give rise to longer-lasting afterimages. This suggests that the apparent brighter sensation of the glare effect is not due to a retinal or LGN mechanism, but must have a cortical origin.