The motion of objects during motion parallax can be decomposed into 2 observer-relative components: translation and rotation. The depth ratio of objects in the visual field is specified by the inverse ratio of their angular displacement (from translation) or equivalently by the inverse ratio of their rotations. Despite the equal mathematical status of these 2 information sources, it was predicted that observers would be far more sensitive to the translational than rotational component. Such a differential sensitivity is implicitly assumed by the computer graphics technique billboarding, in which 3-dimensional (3-D) objects are drawn as planar forms (i.e., billboards) maintained normal to the line of sight. In 3 experiments, observers were found to be consistently less sensitive to rotational anomalies. The implications of these findings for kinetic depth effect displays and billboarding techniques are discussed.

The purpose of the study was to determine the degree to which motor vehicle window tint films impede a police officer's ability to see clearly into a stopped vehicle. Three hundred twenty subjects were asked to view the contents and occupants of one of four experimental cars. One car had no aftermarket tint film, and the other three had aftermarket tint films tinted to various degrees. Although similar experiments have been conducted, all of those experiments yielded equivocal results because of methodological flaws. The present experiment was an attempt to correct some of those problems and to simulate standard procedures used during traffic stops by the Virginia State Police. In general, the study found that the abilities of subjects to detect occupants and objects in vehicles were substantially diminished as the degree of window tinting increased. However, at night the detrimental effects were substantially reduced when headlights and a spotlight were shone on the vehicle, as would be the case in a traffic stop. 

Studies examined infants' perceptions of 3-dimensional form, using a kinetic depth effect (KDE) display and displays containing subsets of the motion present in the KDE display. One subset consisted of “between-contour” motion, and the second consisted of “within-contour” motion. Research with adults has suggested that only between-contour motion leads to a compelling depth percept. In Experiments 1 and 2, infants generalized habituation from a KDE display to the between-contour but not the within-contour changes. In Experiments 3 and 4, infants generalized habituation from a KDE display to the between-contour display viewed from a novel orientation but not to the within-contour display viewed from the original orientation. Results indicate sensitivity to between-contour but not within-contour information, suggesting that infants perceive the 3-dimensional form of these displays.

The logic of judging relative mass from a two-body collision is developed from data presented by Runeson and Vedeler (1993). Data from two experiments are analyzed on a point-by-point basis, and strong support for the theory that mass-ratio judgments are mediated by separate speed and angle heuristics is shown. This analysis is accomplished by reducing the collision event to two elementary features: the presence of ricochet and the ratio of exit speeds. The heuristics that both ricochet and greater exit speed specify relative lightness are shown to explain the basic patterns of data presented by Runeson and Vedeler.

Perceived depth in the stereokinetic effect (SKE) illusion and in the monocular derivation of depth from motion parallax were compared. Motion parallax gradients of velocity can be decomposed into 2 components: object- and observer-relative transformations. SKE displays present only the object-relative component. Observers were asked to estimate the magnitude and near–far order of depth in motion parallax and SKE displays. Monocular derivation of depth magnitude from motion parallax is fully accounted for by the perceptual response to the SKE, and observer-relative transformations absent in the SKE are of perceptual utility only as determinants of the near–far signing of perceived sequential depth. The amount of depth and rigidity perceived in motion parallax and SKE displays covaries with the projective size of the stimuli. The monocular derivation of depth from motion is mediated by a perceptual heuristic of which the SKE is symptomatic.

Principles of perceptual organization can cause simultaneous lightness contrast to be seen in patterns in which the inducing regions are not proximal to the target. In three experiments a match was made between two grey targets, one of which belonged to a white perceptual grouping and the other to a black one. In experiment 1, perceived belongingness was a product of common fate and figural alignment (columns of black dots and columns of white dots moved up and down in counterphase). In experiment 2, belongingness was evoked with only figural alignment. In experiment 3, belongingness was induced by common fate alone. In all three experiments it was found that the grey target belonging to the white group appeared darker than the grey target belonging to the black group.

The present project was designed to follow up an earlier investigation in which perceptual adaptation in response to the use of Night Vision Goggles, or image intensification (I squared) systems, such as those employed in the military were studied. Our chief concern in the earlier studies was with the dynamic visual noise that is a byproduct of the I(sup 2) technology: under low light conditions, there is a great deal of 'snow' or sporadic 'twinkling' of pixels in the I(sup 2) display which is more salient as the ambient light levels are lower. Because prolonged exposure to static visual noise produces strong adaptation responses, we reasoned that the dynamic visual noise of I(sup 2) displays might have a similar effect, which could have implications for their long term use. However, in the series of experiments reported last year, no evidence at all of such aftereffects following extended exposure to I(sup 2) displays were found. This finding surprised us, and led us to propose the following studies: (1) an investigation of dynamic visual noise and its capacity to produce after effects; and (2) an investigation of the perceptual consequences of characteristics of the display media.

In 4 experiments it was found that global frameworks and local distinctive figural characteristics influenced the perception of shape and of pointing. In Experiments 1 and 2, Ss were asked to mark the center of the middle figure in arrays of 3 aligned figures (either triangles or squares). Displacements of the center indicated a perceived deformation of the shapes. In Experiment 3, Ss were asked to adjust the height of triangles in arrays similar to those in Experiment 1. Height adjustments made along the axis of apparent pointing resulted in extents that were shorter than the height necessary to form equilateral triangles. In Experiment 4, stimuli were isosceles triangles in which the apparent distortion had been nulled; however, Ss continued to perceive them as pointing in a direction consistent with their alignment, and hence shape distortion cannot be the cause of pointing.