This paper is a theoretical analysis of eidetic imagery, based upon the author's ten-year study of elementary-school-aged children. The presence of eidetic imagery is inferred from reports of persisting visual images of stimuli when they are no longer in view. According to the criteria for differentiating eidetic images from afterimages, eidetic images should occur even when saccadic eye movements are made during exposure to the stimulus; it should be possible to make saccadic eye movements while one is reporting the image without the image also moving; the image should last long, and it should be positive. The criteria for differentiating eidetic images from nonvisual memorial representations include: reports of seeing an image projected onto a surface in space, the consistent use of present tense when reporting images as opposed to past tense when reporting from nonvisual memory, and the ability to superimpose two images and report the composite image.

Eidetic images are only available to a small percentage of children 6–12 years old, and are virtually nonexistent in adults. However, extensive research has failed to demonstrate consistent correlates between the presence of eidetic imagery and any cognitive, intellectual, neurological, or emotional measure. The negative correlation between eidetic imagery and age has prompted hypotheses to explain eidetic imagery as a developmentally less mature memorial representation, which is gradually replaced by more abstract representations as the child acquires abstract thought, reading, and more advanced cognitive abilities. The evidence in the present review casts doubt on this hypothesis on numerous grounds: an extensive longitudinal study over the entire span of elementary school years found that eidetic abilities remain remarkably stable; there is no correlation between eidetic imagery and abstract thinking or reading performance; there is no higher incidence in preschool ages, among retarded or brain-injured subjects, or among illiterate subjects in crosscultural studies.

It is concluded that we should not abandon work on eidetic imagery or simply force it into a preconceived mold of what memory must be, but rather, expand work on the phenomenological indicators of perception and memory.

Psychophysical research has documented the existence of three processes in light adaptation: a fast subtractive process, a divisive process that is fast at light onset and slower at light offset, and a very slow subtractive process (Hayhoe et al., 1987). In the neural model developed here, the fast subtractive process is identified with horizontal cell feedback onto cones and the divisive process with amacrine cell feedback onto bipolar cells. The very slow subtractive process is identified with the modulatory feedback circuit from amacrines via interplexiform cells to horizontal cells. A nonlinear dynamical model is developed incorporating these aspects of retinal circuitry along with both ON- and OFF-center M and P pathways. This model is shown to account for many aspects of foveal light adaptation, including negative afterimage formation, and to explain a number of the physiological differences between M and P ganglion cells, including their differing contrast-response functions.

This study examined the consequences of visual system lesions on visual aftereffects produced by achromatic stimuli of various luminance contrasts and chromatic stimuli of various wavelength compositions. The effects of repeated exposure to such adapting stimuli were assessed using probes whose luminance contrast and wavelength composition were systematically varied using both detection and discrimination paradigms. Interocular tests revealed that both peripheral and central mechanisms contribute to the visual aftereffects produced by the adapting stimulus arrays used in this study. Contrary to the hypothesis according to which the midget system of the retina is the conveyor of visual afterimages, we found that blocking this system with lesions of parvocellular lateral geniculate nucleus, through which the midget cells make their way to the striate cortex in primates, did not eliminate the visual aftereffects. It appears therefore that the parasol system of the retina, which courses through the magnocellular layers of the lateral geniculate nucleus to cortex, can convey the necessary signals for the generation of visual aftereffects. Lesions of areas V4 and MT did not have significant effects on the visual aftereffects studied suggesting that the central factors that contribute to the visual aftereffects occur either already in area VI or are conveyed to higher centers through regions other than areas V4 and MT.