Perceiving the Center of Three-Body Displays: The Role of Size-Ratio, Symmetry, Elongation, and Gravity

Participants judged the perceived center of three-dot displays at different orientations. In Experiment 1, the dots formed an equilateral triangle. The direction of the response distribution aligned with the largest dot, along axes of reflectional symmetry and with the gravitational down. In Experiment 2, we created isosceles triangles where the distance between one of the dot pairs was varied. Errors were higher for configurations where the symmetry axis was horizontal and a virtual elongation axis was vertical. The results of Experiment 3 replicate this finding and show that response direction is an accommodation to gravity and other shape factors.