The effects of optical compression and magnification on distance estimation

When moving through space, both visual and non-visual information can be used to monitor distance traveled. It is important, although challenging to dissociate the relative contributions of each of these cues when both are available in natural, cue-rich environments. This study created a conflict between visual and non-visual distance cues by either magnifying (2×) or compressing (0.5×) the information contained in the optic array using spectacle-mounted lenses. The experiment took place in a long, wide hallway, relatively void of visual landmarks. Subjects (Ss) were required to view a static target in the distance (4, 6, 8, 10m) and reproduce this distance by walking. Ss experienced four optical conditions (2×, 0.5×, 1×, or no lenses) either during the visual preview (Exp 1) or during the walked response (Exp 2). In Exp 1, Ss viewed the target distance under each of the four optical conditions and produced their estimates by walking blindfolded. In Exp 2, Ss viewed the target distance without lenses and produced their estimate by walking under each of the four optical conditions. In Exp 1, when wearing the 2× lenses during visual preview, Ss produced estimates that were significantly shorter than those produced when wearing 1× or no lenses. The opposite was true when wearing the 0.5× lenses. In Exp 2, however, regardless of the optical manipulation, Ss' estimates remained essentially unchanged, thus suggesting a reliance on non-visual cues. Such findings may reflect the tendency for subjects to weigh more reliable cues higher in their final estimate