Biomedical subjects
Publications and source records attributed to D Piggins.
The reports and depiction of the vision and refraction of sheep by Lewis Carroll in Through the looking glass and what Alice found there (1871) appear to be at the very least optically ambiguous in the light of our contemporary knowledge of the refraction of the sheep eye with its large pupil and lack of accommodation and pupil closure.
Here a new depth effect evoked by the spatial and temporal interaction in 2-D of a slowly moving circle (optimally at 0.6 rads/sec) with an identical static circle is reported. Typically, respondents report that with increasing adjacency, commencing with separations of a few diameters, the moving circle appears in a different plane of depth to the static circle, it then usually appears to "dip" onto the static circle and after complete coincidence with it to rise away from it. This effect, together with a number of associated descriptions are commented upon, in addition to observations when viewing overlapped static circles and overlapped circles in motion, this latter stimulus condition evoking the stereokinetic effect. The authors have previously suggested that contour "sliding," which simulates motion parallax, is the key to understanding stereokinesis. The stimulus conditions giving rise to this new effect directly simulate the motion parallax information present in a retinal image.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Moiré patterns in depth are reported when spatially periodic stimuli are viewed stereoscopically. Near-vertical square-wave gratings with horizontal disparity effected by orientation difference produce a 'venetian blind' effect. A single grating is observed divided into horizontal layers, the number of layers being a direct function of orientation difference. Lines within each layer are slanted with respect to the frontoparallel plane, becoming more so with increasing orientation difference. Subjects with stereo deficits report a decreased effect. Quantitative reports implicate stereoscopic mechanisms responsible for this unique, internal preservation of moiré patterns.
The techniques of steady visual fixation and repetitious auditory input are used in the laboratory for investigating perceptual phenomena and in yoga and meditation for facilitating altered states of awareness. Phenomena related to mild sensory deprivation are reported in both circumstances.
The Binocular Pinhole Device requires binocular vision, without constraints on head-movements, for viewing a group of letters at one fixation. It is simple and adjustable for individual differences. The role of peripheral vision can be explored in experimental settings.