Perception of two-body center of mass

Abstract

Participants estimated the perceptual center of mass between two horizontally oriented black dots varying in size and distance. Experiment 1 showed that estimates,measured as distance from the larger dot's center, decreased with an increase in size ratio between the dots and a decrease in the distance between them, as predicted by the physical center-of-mass equation. The results were replicated and extended in further experiments with different ratios and distances. In all experiments, the true center was consistently overestimated, either because the stimuli were perceived in a low dimensionality or because of a hesitancy to place estimates near the larger dot's edge. In Experiment 4, the center was deliberately placed near this edge for one-and two-dimensional solutions. Participants still overestimated, indicating an "edge effect" as responsible.

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

“…The use of this type of configuration has allowed us to manipulate a number of factors including relative dot size and the number, length, and orientation of symmetry and elongation axes. It has extended our previous findings with size ratio to patterns with more than two dots [11].…”

“…However, dot separation does affect center-of-mass estimation. In previous work, we found strong distance effects for two dot patterns [11]. As separation between two dots of differing sizes decreases, estimates move correspondingly closer to the larger dot, tracking changes in the true center position.…”

“…In previous work using two dot displays, we found that center of mass judgments were affected systematically by dot size ratio and separation [11]. Participant's estimates were remarkably accurate, meaning close to the true center location, except for when the true center fell close to the larger dot's edge, indicating a reluctance to place estimates near or inside one of the dots.…”

“…First, we wish to investigate the role size ratio plays in patterns with more than two dots. In our earlier study, responses were always attracted to the larger of two masses [11]. With three dots we can investigate more complicated situations such as when two dots are equal but larger in mass than a third.…”

Precise attention filters for Weber contrast derived from centroid estimations

“…Stimuli that consist of spatially extended targets have been utilized in investigations of attention and visual processing (e.g., Cohen, Schnitzer, Gersh, Singh, & Kowler, 2007), and subjects have revealed the ability to accurately locate the center of mass of a target (e.g., Baud-Bovy & Soechting, 2001;Friedenberg & Liby, 2002). In our task, observers estimate the centroid (the center of gravity) of a cloud of dots flashed on a screen.…”