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 tex tured background (consisting of contrasting vertical stripes) was used. Vel ocity modulations occurred so as to keep the angle beta between the directi on of heading and the line head-ball constant (constant bearing angle, or C BA strategy), indicating that this observer-environment relation might regu late the approach phase. In the textured condition, participants initially drove faster than predicted by the CBA model and compensated by slowing dow n in the second half This is in line with the texture-induced overestimatio n of the ball velocity and implies that absolute velocity information is al so used.