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EFFECT OF COMBINATIONS OF SIX PRESENTATION CONDITIONS ON THE DURATION OF THE SPIRAL AFTEREFFECT,
COLBY COLL WATERVILLE MAINE
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Using the stationary spiral itself as a test object 8 ft. from S, the duration of the spiral aftereffect was measured in three experiments which varied diameter, direction and speed of rotation of spiral, inspection time, number of turns and relative proportion of black and white. Duration of the aftereffect increased as number of turns of the spiral increased from 1.5 to 3.5, as inspection time increased from 15 - 120 sec. and as the relative width of light and dark bands decreased from 15 to 51. The aftereffect was longer with the expanding condition than with the contracting one. It decreased as spiral diameter changed from 4 or 8 to 16 in. corresponding to changes in visual angle ranging from 2 degrees to 9 degrees. Speeds of 25, 100 and 250 RPM did not produce significant differences although an interaction was found between speed and number of turns. Author
APPROVED FOR PUBLIC RELEASE