Static and dynamic factors in the perception of rotary motion

Direction of rotation and static slant judgments were collected for a series of outline plane forms in four experiments with 106 subjects. Direction was judged more accurately for forms displaying the same perspective gradients as trapezoids, but with right-angled contours, than for trapezoids. There were no consistent differences among these forms in judged slant. Direction of rotation judgments were affected by a static false interposition cue, with interposition increasing the proportion of veridical judgments when placed in conflict with a relative size gradient and decreasing this proportion when a size gradient was absent. Both a dynamic factor (contour angle change) and a static factor (misperceived relative distance of the vertical sides) were found to affect perceived direction of rotation, with direction judgments based primarily on the dynamic factor.     

The ground dominance effect in the perception of relative distance in 3-D scenes is mainly due to characteristics of the ground surface

Previously, we (Bian, Braunstein, and& Andersen, 2005) reported a dominance effect of the ground plane over other environmental surfaces in determining the perceived relative distance of objects in 3-D scenes. In the present study, we conducted three experiments to investigate whether this ground dominance is due to inherent differences between ground and ceiling surfaces, or to the locations of these surfaces in the visual field. In Experiment 1, two vertical posts were positioned between a ground surface and a ceiling surface, and optical contact was manipulated so that the two surfaces provided contradictory information about the relative distances of the posts from the participant. The two surfaces were either both above, both below, or one above and one below fixation. In Experiment 2, only one surface was presented, either above, below, or at fixation. In Experiment 3, the posts were replaced by two red dots, and the eccentricity of the optical contact on the two surfaces was equated in each of five locations in the visual field. In all three experiments, participants judged which of the two objects appeared to be closer. Overall, we found a higher proportion of judgments consistent with a ground surface than with a ceiling surface in all locations, indicating that the ground dominance effect is mainly due to characteristics of the ground surface, with location in the visual field having only a minor effect.     

The ground dominance effect in the perception of 3-D layout

The relative effectiveness of the ground surface and other environmental surfaces (the ceiling and sidewalls) in determining perceived layout was investigated in five experiments and a real-world demonstration. In the first three experiments, two vertical or horizontal posts were positioned between two surfaces (ground and ceiling in all three experiments, left wall and right wall in Experiment 1), and optical contact was manipulated so that the two surfaces provided contradictory information about the relative distances of the posts. Observers judged which of the two posts appeared to be closer. In Experiment 4, to control the height on the posts at which the distance judgments were made, a blue dot was attached to both vertical posts at varying heights and observers judged which dot appeared closer. In Experiment 5, the posts were replaced by two gray ellipses to eliminate the effects of the regular shape and texture. Our findings were that (1) among all four surfaces tested, observers showed a preference to respond according to the optical contact information provided by the ground surface--a ground dominance effect, (2) this effect did not depend on the height of the posts in the image, (3) as the scene was tilted away from a ground/ceiling orientation, the ground dominance effect decreased, and (4) this effect was not due to the location of the judgment.     

Time Flies When You're Having Approach-Motivated Fun: Effects of Motivational Intensity on Time Perception

Time flies when you're having fun, but what is it about pleasant experiences that makes time seem to go by faster? In the experiments reported here, we tested the proposal that approach motivation causes perceptual shortening of time during pleasant experiences. Relative to a neutral state or a positive state with low approach motivation (Experiment 1), a positive state with high approach motivation shortened perceptions of time. Also, individual differences in approach motivation predicted shorter perceptions of time. In Experiment 2, we manipulated approach motivation independently of the affective state and showed that increasing approach motivation caused time to be perceived as passing more quickly. In Experiment 3, we showed that positive approach motivation, as opposed to arousal, shortens perception of time by comparing a highly arousing positive state with a highly arousing negative state. Shortening of time perception in appetitive states may prolong approach-motivated behavior and increase the likelihood of acquiring appetitive objects or goals.