The role of tone duration in dichotic temporal order judgment

Over the past two decades, a number of studies have been based on the dichotic temporal order judgment (TOJ) paradigm, to compare auditory temporal processing in various subpopulations to that of young, normal controls. The reported estimates of dichotic TOJ thresholds, expressed as the interstimulus intervals (ISIs) for 75 % accuracy among the controls, have varied. In the present study, we examined the influence of tone duration, within the 10- to 40-msec range, on dichotic TOJ accuracy and threshold. The results indicated that increases in either ISI or tone duration increased dichotic TOJ accuracy similarly, implying that changes in tone duration may affect dichotic TOJs simply by adding to the delay between onset of the tone at the lead ear and onset of the tone at the lag ear. The dichotic TOJ thresholds from three published studies that had used tones as stimuli and the dichotic thresholds from the present study all fell within 0.5 standard deviations from the theoretical line of a 10-msec reduction in threshold for every 10-msec increase in tone duration. When the dichotic TOJ threshold data from the present study and from the published studies were converted to stimulus onset asynchronies (SOAs) and plotted as a function of tone duration, they fell very close to or on a zero-slope line, indicating that when ISI and duration are summed to yield an SOA, dichotic TOJ thresholds are invariant to tone duration within the range of 10-40 msec.