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Subjects rated the strength of the motion aftereffect (MAE) produced by the upward motion of a horizontal grating in two experiments. Inspection periods ranged from 30 to 900 sec in Experiment 1 and from 20 to 120 sec in Experiment 2. A minimum of 22 h elapsed between trials. The decay time constant increased as the square root of the inspection duration for values between 1 min and 15 min of inspection. The ratings suggested that the MAEs consisted of three phases: an initial maximum-strength phase, a decay phase, and a tail. The duration of all three phases increased and the decay rate decreased with increasing inspection duration over the entire range. The results indicate that duration, time constant, and decay rate are not fixed properties of the motion-processing channels in the visual system.

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The moon illusion and the spiral aftereffect are illusions in which apparent size and apparent distance vary inversely. Because this relationship is exactly opposite to that predicted by the static size--distance invariance hypothesis, the illusions have been called "paradoxical." The illusions may be understood as products of a loom-zoom system, a hypothetical visual subsystem that, in its normal operation, acts according to its structural constraint, the constancy axiom, to produce perceptions that satisfy the constraints of stimulation, the kinetic size--distance invariance hypothesis. When stimulated by its characteristic stimulus of symmetrical expansion or contraction, the loom-zoom system produces the perception of a rigid object moving in depth. If this system is stimulated by a rotating spiral, a negative motion-aftereffect is produced when rotation ceases. If fixation is then shifted to a fixed-sized disc, the aftereffect process alters perceived distance and the loom-zoom system alters perceived size such that the disc appears to expand and approach or to contract and recede, depending on the direction of rotation of the spiral. If the loom-zoom system is stimulated by a moon-terrain configuration, the equidistance tendency produces a foreshortened perceived distance for the moon as an inverse function of elevation and acts in conjunction with the loom-zoom system to produce the increased perceived size of the moon.

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Newborn humans presented with pairs of shapes, each shape differing in number of turns (angles), prefer shapes with 10 turns to shapes with 5 turns or 20 turns, as inferred from photographic recordings of eye fixations.