Strength of onset and ongoing cues in judgments of lateral position.

This study describes the contributions to auditory image position of an interaural time delay (ITD) cue at onset relative to subsequent ITDs during the ongoing part of a stimulus. Test stimuli were trains of 1-ms binaural noise bursts; lateral position was measured with a wideband acoustic pointer that subjects adjusted to match the intracranial position of test stimuli. In different conditions the ongoing part of the stimulus (the bursts following the first one) either had a consistent ITD (the same ITD on each ongoing burst), or had alternating leading and lagging components with ITDs that opposed one another. As duration of the ongoing part was increased from 4 to 250 ms, with the initial ITD fixed, lateral position changed from being dominated by the onset ITD to being dominated by the ongoing consistent or leading ITD. With alternating ongoing ITDs equal contributions from onset and ongoing parts were obtained at an ongoing duration of about 40 ms; with consistent ongoing ITDs equal contributions were obtained at about 15 ms. The results point up the increased dominance of onset cues when ongoing cues are ambiguous, as they often are in real-world settings.