Retinal vs. environmental orientation in the perception of the right angle.

The right angle is perceived as such only when its sides are vertical and horizontal (Goldmeier effect). We investigated if spontaneous verbal descriptions reflect this type of "oblique effect", and if the relevant frame of reference is retinal or environmental. We compared four conditions in which upright vs. tilted observers were asked to describe gravitationally normal vs. oblique angles. It is shown that the Goldmeier effect depends upon the environmental coordinates, which usually determine the orientation of the subjective frame of reference. We argue that the singularity of the right angle in the vertical/horizontal orientation depends on a phenomenological fact: only the normal right angle looks like a right angle.