Academic journal article Attention, Perception and Psychophysics

Effects of Changes in Size, Speed, and Distance on the Perception of Curved 3-D Trajectories

Academic journal article Attention, Perception and Psychophysics

Effects of Changes in Size, Speed, and Distance on the Perception of Curved 3-D Trajectories

Article excerpt

Abstract Previous research on the perception of 3-D object motion has considered time to collision, time to passage, collision detection, and judgments of speed and direction of motion but has not directly studied the perception of the overall shape of the motion path. We examined the perception of the magnitude of curvature and sign of curvature of the motion path for objects moving at eye level in a horizontal plane parallel to the line of sight. We considered two sources of information for the perception of motion trajectories: changes in angular size and changes in angular speed. Three experiments examined judgments of relative curvature for objects moving at different distances. At the closest distance studied, accuracy was high with size information alone but near chance with speed information alone. At the greatest distance, accuracy with size information alone decreased sharply, but accuracy for displays with both size and speed information remained high. We found similar results in two experiments with judgments of sign of curvature. Accuracy was higher for displays with both size and speed information than with size information alone, even when the speed information was based on parallel projections and was not informative about sign of curvature. For both magnitude of curvature and sign of curvature judgments, information indicating that the trajectory was curved increased accuracy, even when this information was not directly relevant to the required judgment.

Keywords Motion: In Depth . 3D perception

(ProQuest: ... denotes formulae omitted.)

Published online: 25 September 2012

© Psychonomic Society, Inc. 2012

Human observers are able to use the information in projections of 3-D motion to make judgments about the trajectories of objects moving in the 3-D world. Accurate perception of object motion in 3-D is important in many real world applications, such as traffic safety and sports. Much of the research on the perception of motion trajectories has been concerned with the accuracy of judgments about approaching objects, such as time to contact (Lee, 1976), time to passage (Kaiser & Hecht, 1995; Kaiser & Mowafy, 1993), collision detection (Andersen, Cisneros, Atchley, & Saidpour, 1999; Gray & Regan, 1998; Ni & Andersen, 2008; Regan & Gray, 2000), speed and direction of motion (Brooks & Stone, 2006; Harris & Drga, 2005; Rushton & Duke, 2009), and the prediction of the future trajectory (Craig, Berton, Rao, Fernandez, & Bootsma, 2006; Craig et al., 2009). The types of information that have been studied include optical motion, to be discussed below, binocular disparity (Rushton & Duke, 2007; Rushton & Wann, 1999; Warren & Rushton, 2009), and scene-based information (Meng & Sedgwick, 2001, 2002; Ni, Braunstein, & Andersen, 2004, 2005).

Gibson demonstrated that observers can pick up many aspects of motion in the 3-D world from 2-D optical patterns (Gibson, 1950, 1966, 1979). Mathematical analyses have indicated that properties of 3-D motion can be recovered from optical motion alone (D. Regan & Kaushal, 1994; Todd, 1981). When optical motion is the only information available, properties of the motion can in theory be recovered from changes in angular size and changes in projected position. Todd (1981) showed that if the distance from a planar projection surface to the observation point is set to unity and object rotation is not considered, the object's approach angle (γ) relative to the horizontal axis is given by

...(1)

where Y is the vertical projected distance from the edge of the object to the observer, R is the projected width of the object, and VY and VR are the time derivatives of Y and R. Equation 1 indicates that the trajectory of the object's motion can be recovered in principle from optical motion alone. Regan and Kaushal also proposed that the direction of motion in depth can be quantified from information in a monocular retinal image. …

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