Intercepting moving objects during self-motion: effects of environmental changes.

The purpose of this study was to examine the role of background texture on an interception task during self-motion. Twenty-six participants modulated tricycle speed along one arm of a V-shaped track so as to intercept a ball approaching horizontally on the other arm of the V. Either a plain or a textured background (consisting of contrasting vertical stripes) was used. Velocity modulations occurred so as to keep the angle beta between the direction of heading and the line head-ball constant (constant bearing angle, or CBA strategy), indicating that this observer-environment relation might regulate the approach phase. In the textured condition, participants initially drove faster than predicted by the CBA model and compensated by slowing down in the second half. This is in line with the texture-induced overestimation of the ball velocity and implies that absolute velocity information is also used.