The Perky effect, identified in 1910, is the reduction in performance from the no-imagery to the imagery condition. A series of experiments with over 100 undergraduates and graduates shows that the reduction reflects a true reduction in visual sensitivity, not just alteration in criteria for responding or response organization. (SLD)

This paper reviewed briefly the major types of masking effects obtained with various methods and the major theories or models that have been proposed to account for these effects, and outlined a three-mechanism model of visual pattern masking based on psychophysical and neurophysiological properties of the visual system. (Author/RK)