Abstract
Variations in sound frequencies can cue up or down visual locations even when visual stimuli are unambiguous. However, it is not clear whether this crossmodal phenomenon occurs for non-cardinal directions, or whether the processes underlying it derive from an allocentric or egocentric representation of visual space. To investigate these questions, we used a yes/no color-matching task that participants performed either with their heads upright (matched allo- and egocentric axes) or tilted 90-degrees (disassociated allo- and egocentric axes). Specifically, the first of two colored discs was presented at fixation and the second was presented in one of four positions equidistant from fixation (colors matched on 70% of trials). Brief sounds (500 ms) changing from low-to-high pitch or high-to-low pitch were played over headphones; these frequency-modulated sweeps began at the onset of the first disc and ended at the onset of the second. Participants were told to respond to the color match between the two discs and ignore the uninformative sounds. The location of the second disc was in one of four cardinal directions (Upper, Lower, Right, Left) or four ordinal directions (Upper-Left, Upper-Right, Lower-Left, Lower-Right). The low-to-high sweeps speeded responses to the Upper disc (also the Right disc to a lesser degree), and the high-to-low sweeps speeded responses to the Lower disc (also the Left disc to a lesser degree); these effects were driven by pitch change rather than absolute pitch. The sweeps had no effects on ordinal disc locations, and the head tilt eliminated the sound-sweep effects at all locations. Thus, visual-spatial cueing by pitch change is specific to cardinal directions, this cuing occurs only when allo- and egocentric axes are aligned, and the multisensory integration processes contributing to this effect may result from associative learning during everyday upright experience.
NSF BCS0643191, NIH R01EY018197-02S1.