Abstract:

The minimum audible angle (MAA) thresholds obtained by Mills [A. W. Mills, J. Acoust. Soc. Am. 30, 237--246 (1958)] involved two 1000-ms sinusoidal tone pulses presented sequentially with an interstimulus interval (ISI) of 1000 ms. In contrast to the generally good localization performance obtained by Mills, localization of two simultaneous events (concurrent localization or CMAA) results in relatively poor performance [D. R. Perrott, J. Acoust. Soc. Am. 76, 1704--1712 (1984)]. The current set of experiments attempts to bridge the gap between these two extreme paradigms. While the target tones (14-ms, 1000-Hz sinusoids) were presented sequentially (an MAA task), an attempt was made to systematically examine the consequences of the addition of a nonoverlapping, auditory event (tones or noise) during the interval between the target events. The results of this work indicate that localization performance is extremely sensitive to events that occur between the target events. The disruptive effect of a ``nontarget'' event during the ISI could even be observed when relatively long ISIs (814-ms) and very brief (14-ms) distractors events were used. Interesting interactions were encountered as a function of the spatial positioning of the nontarget (``distractor'') event. Implications of these results will be discussed.