Monaural vs diotic stimulus presentation

["Susan E. Hall" <susanhal@xxxxxxxxx>]

When designing a psychophysical study of a monaural phenomenon, that
is, one in which binaural information does not play a part, I've
noticed that almost everyone presents their (headphone) stimuli
monaurally. I was wondering if anyone can give me good reasons for
not presenting the stimuli diotically, that is, the same stimulus
presented to both headphone channels.

Specifically, I'm designing a study on temporal gap detection, using
noise markers of various bandwidths. I'm interested in relative
performance as a function of the noise marker composition. So, if the
absolute gap detection thresholds across the board were lower with
diotic than monaural presentation, due to some sort of summation
effect, it wouldn't matter to me.

The reason I even ask, is that for the subjects, listening to a
midline intracranial sound image is SO much more comfortable than
listening to sounds at one ear. When you're asking subjects to make
tens of thousands of judgements, this actually becomes an issue. If
there were no theoretical reason for sticking to monaural stimulus
presentation, then I would like to present the stimuli diotically,
but I want to be sure I'm not creating a problem with this first.
Thanks!

Susan Hall
Dalhousie University