Investigations of the precedence effect in budgerigars: the perceived location of auditory images.

The perceived location of auditory images has been recently studied in budgerigars [Dent and Dooling, J. Acoust. Soc. Am. 113, 2146-2158 (2003)]. Those results suggested that budgerigars (Melopsittacus undulatus) perceive precedence effect stimuli in a manner similar to humans and other animals. Here we extend those experiments to include the effects of intensity on the perceived location of auditory images and the perceived location of paired stimuli from multiple locations in space. We measured the abilities of budgerigars to discriminate between paired stimuli separated in time, intensity, and/or location. Increasing the intensity of a lag stimulus disrupted localization dominance. Budgerigars also perceived simultaneously presented (away from the midline) stimuli as very similar to a single sound presented from the midline, much like the phantom image reported in humans. The perception of paired stimuli from one side of the head versus two sides of the head was also examined and showed that the spatial cues available in these stimuli are important and that echoes are not perceptually inaccessible during localization dominance conditions. The results from these experiments add further data showing the precedence effect in budgerigars is similar to that found in humans and other animals.