Functional Specificity of the Affordance of Reaching.

The information that specifies whether an object is within reach is a complex pattern that depends on body-scaled parameters measured from an egocentric reference point. The pattern is a function of relevant body proportions (eye height, shoulder height [SH], arm length) with respect to the spatial location of the target object. In addition to not knowing how these factors map onto perception, it is also not known whether the egocentric viewpoint is centered at the eye or the shoulder.