Abstract
Introduction: This study tests conditions conducive for spatial illusions in a naturalistic, 3-D, real-world, baseball setting. We examined perceptual judgments of ground ball destinations by peripheral stationary observers compared to nearby active fielders. Methods: A 3m by 21m tarp covered a barricade between 1st and 2nd base, 0.5m off the ground. Participants estimated where ground balls from home plate would emerge if not for the barricade. 0, 1, 2, or 4 simultaneous baserunners ran perpendicular to the ground balls to test for induced motion effects under real-world sporting conditions. 112 participants over three experiments observed and estimated where the ball would exit from under the tarp if there were no barrier. Active participants ran along the back edge of the tarp touching it above where they believed the ball would have exited. Results: Our findings revealed a robust kinetic Poggendorff illusion (offset mean=74cm) for stationary observers that only minimally diminished when they were near the ball destination location, but no significant distortion occurred for active fielders (offset mean=5cm). In addition, though there were no significant differences between the 1, 2, or 4 baserunner conditions, their average produced robust illusory motion opposite the direction of the baserunners (offset mean=35cm), but that once again produced no significant distortion for the active fielders (offset mean=8cm). Discussion: The findings confirm robust spatial illusions occur in naturalistic, real-world environments like a baseball setting, but only for stationary observers and not active moving fielders. The findings are consistent with other research that supports two independent perceptual systems, an illusion-prone ventral or "what" system used for constructive stationary predictions of space, and an illusion-resistant dorsal or "how" system used to control ongoing, interactive perception-action movements. The findings support that robust spatial illusions occur in real-world sport settings, but generally not with sporting actions.
Meeting abstract presented at VSS 2017