FIGURE 3.

The perceived direction of auditory “up” (A) corresponds to the perceptual upright which is determined by a combination of the body idiotropic vector and gravity with more emphasis on the body (Dyde et al., 2006). Non-spatial sounds differing only in their frequency content were used to disambiguate ambiguous visual motion created by superimposing two gratings moving in opposite directions either vertically (B) or horizontally (C) viewed by an observer lying on their side. The effect of sound in shifting the contrast balance for “ambiguous motion” from 50:50 provided the horizontal and vertical components of the perceived direction of sound.