Which Direction Is up for a High Pitch?

Abstract

Low- and high-pitched sounds are perceptually associated with low and high visuospatial elevations, respectively. The spatial properties of this association are not well understood. Here we report two experiments that investigated whether low and high tones can be used as spatial cues to upright for self-orientation and identified the spatial frame(s) of reference used in perceptually binding auditory pitch to visuospatial ‘up’ and ‘down’. In experiment 1, participants’ perceptual upright (PU) was measured while lying on their right side with and without high- and low-pitched sounds played through speakers above their left ear and below their right ear. The sounds were ineffective in moving the perceived upright from a direction intermediate between the body and gravity towards the direction indicated by the sounds. In experiment 2, we measured the biasing effects of ascending and descending tones played through headphones on ambiguous vertical or horizontal visual motion created by combining gratings drifting in opposite directions while participants either sat upright or laid on their right side. Ascending and descending tones biased the interpretation of ambiguous motion along both the gravitational vertical and the long-axis of the body with the strongest effect along the body axis. The combination of these two effects showed that axis of maximum effect of sound corresponded approximately to the direction of the perceptual upright, compatible with the idea that ‘high’ and ‘low’ sounds are defined along this axis.