Maurice Hershenson

Duration, time constant, and decay of the linear motion aftereffect as a function of inspection duration

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 Ex-periment 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 be-tween 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.

Linear and rotation motion aftereffects as a function of inspection duration

Subjects rated the strength of linear and rotary motion aftereffects (MAEs) on an eleven point scale. Inspection durations ranged from 30 to 180 sec in 30 sec steps. In Expt 1, trials using a single inspection duration were spaced at least 22 hr apart to minimize the possibility of interactions between adapting stimuli and long lasting aftereffects. In Expt 2, a counterbalanced sequence of inspection durations was completed in a single session. Total duration of the MAE and durations of the decay phase and tail were measured directly. The decay time constant (DTC), the time it takes for rated strength of the MAE to drop to 1/e of its initial value, was calculated from a line fit to a semilog plot of the ratings during the decay phase. The DTC is inversely related to the decay rate which is indexed by the slope of this line. In both experiments, the duration and DTC increased, and decay rate decreased, with increasing inspection duration for both rotary and linear MAEs. This finding replicates the results for linear MAEs and extends them to rotation MAEs. There were no discernible differences between the two types of MAEs. When the trials were spaced, the total duration increased with the square root of inspection duration. The DTC did not follow the square root rule over the entire range but appeared to approximate it for inspection durations of 90 sec and above. When trials were massed, the square root rule did not appear to apply at all.

Visual system responds to rotational and size-change components of complex proximal motion patterns

The qualitative and quantitative characteristics of rotation, contraction, and motion-in-depth motion aftereffects (MAEs) produced by rotating Archimedes spirals were compared for spirals differing in arm length (90°, 270°, and 720°). There were three test stimuli. The spokes and rings test stimuli were figures whose contours were orthogonal to the direction of motion of the MAEs produced by the rotational and radial components of the spiral’s motion, respectively. The floating disk test stimulus was used to test for a motion-in-depth MAE. In Experiment 1, naive subjects viewed the spirals for 30 sec and 3 min. The MAE components reported corresponded to the rotational and radial components of motion in the proximal stimulus. In Experiment 2, experienced subjects were used to measure decay time constants (DTCs) after 15 min of adaptation. The rotation MAE had a DTC that was shorter than the other two DTCs. Results support the hypothesis that the complex stimulus produced by rotating Archimedes spirals is resolved into rotational and radial components by structures in the visual system that are specifically sensitive to rotational and size-change relative motion patterns (Regan, 1986). They also support Hershenson’s (1982) suggestion that the spiral aftereffect is produced by the same perceptual structures that mediate the perception of rigid object motion in depth.

Phantom spiral aftereffect: Evidence for global mechanisms in perception

The existence of phantom motion aftereffects (MAEs) makes it difficult to explain normal MAEs in terms of the activity of simple motion detectors. The alternative is to assume that MAEs are mediated by larger structures that respond more broadly to stimulus input. In this view, normal and phantom MAEs are manifestations of activation of a single structure and, therefore, should not differ in their qualitative and quantitative properties. This hypothesis was tested in two experiments, one that used experienced subjects and one that used naive subjects. The adapting stimulus was the upper half of a rotating spiral. Normal spiral aftereffects (SAEs) were observed over the upper half of a set of concentric circles; phanton SAEs were observed over the lower-half semicircles. Subjects continuously rated the strength of the aftereffect on an 11-point scale. The ratings were recorded every 5 sec. All subjects reported seeing normal and phantom SAEs in the appropriate respective directions. Rates of recovery from adaptation were remarkably similar. The results support the hypothesis that normal and phantom SAEs are a manifestation of activity in a structure larger than a simple motion detector.

Size-distance invariance: kinetic invariance is different from static invariance.

The static form of the size-distance invariance hypothesis asserts that a given proximal stimulus size (visual angle) determines a unique and constant ratio of perceived-object size to perceived object distance. A proposed kinetic invariance hypothesis asserts that a changing proximal stimulus size (an expanding or contracting solid visual angle) produces a constant perceived size and a changing perceived distance such that the instantaneous ratio of perceived size to perceived distance is determined by the instantaneous value of visual angle. The kinetic invariance hypothesis requires a new concept, an operating constraint, to mediate between the proximal expansion or contraction pattern and the perception of rigid object motion in depth. As a consequence of the operating constraint, expansion and contraction patterns are automatically represented in consciousness as rigid objects. In certain static situations, the operation of this constraint produces the anomalous perceived-size-perceived-distance relations called the size-distance paradox.

An Airplane Illusion: Apparent Velocity Determined by Apparent Distance

When a small drone plane appears to be a normal-sized airplane, it appears to be very far away and moving too fast. This is the airplane illusion. In the illusory situation, familiar size determines the apparent size and distance of the plane. It sets the depth for the frontal-plane component of the perceived motion and the relative depth difference for the motion-in-depth component. Because these perceived distances are very large, the perceived velocities are very large in the respective directions. Cognition can override familiarity and produce a veridical perception of the drone.

Size-distance perception in preschool children☆

Abstract Children between three and six years of age matched the “apparent” and “real” size of familiar and unfamiliar objects 3, 6, or 9 feet away. Prior to the experimental sessions, the children were divided into two groups: (a) those who could distinguish the phenomenal from the real sizes of the arcs in the Jastrow illusion (the “Realists”) and (b) those who could not (the “Phenomenalists”). The results suggest that all children perceived size constancy up to distances of 9 feet solely on the basis of visual information.

Thirty seconds of adaptation produce spiral aftereffects three days later

Subjects fixated the center of a rotating spiral for 30 sec. They returned 1, 2, or 3 days later to view one of three test targets: spokes, concentric rings, or a floating disk. Seventeen of 18 subjects reported long-term spiral aftereffects whose motion components were similar to those of the short-term spiral aftereffect.

Structural Constraints: Further Evidence from Apparent Motion in Depth

The three-dimensional (3-D) apparent motion of lines, outline triangles, and light points was studied in four experiments. The stimulus sequences were beginning and end patterns of 3-D motions of a line and a triangle. Light-point patterns corresponded to the ends of the lines and the vertices of the triangles. Perceived motion of lines and light-point pairs resembled the distal motions that were used to construct the proximal patterns. The correspondence was striking for configurations that appeared to move in depth. Outline triangles and light-point triplets produced a strong correspondence between distal and perceived motions when the three sides appeared to be translating in depth. The correspondence was reasonably good for the other motion patterns when scoring included an appropriate second category. The results support the conception of structural or internalized constraints: light points were processed as if they were connected (unity constraint) and proximal change in linear size (or distance between light points) was perceived as rigid 3-D motion (rigidity constraint).

DIRECTIONAL SYMMETRY IN THE SPIRAL AFTEREFFECT

The duration of the spiral aftereffect was measured after 1, 2, and 5 min. of adaptation for “inward” and “outward” rotation of the spiral. Duration of the aftereffect increased as adaptation time increased but the direction of rotation of the spiral had no effect.