Re: Interesting dichotic effect

[robert bolia <rbolia@xxxxxxxxxxx>]

Mitch,
  I haven't had time to give this a lot of thought, but maybe it has
something to do with a laterality effect.  I seem to remember the suggestion
by Sidtis that some aspects of pitch perception are lateralized to the right
hemifield.  It may then be the differences are due to differences in
processing across hemifields (assuming stronger crossed pathways than
uncrossed pathways). Anyway, here are the references:

Sidtis, J. (1980).  On the nature of the cortical function underlying right
hemisphere auditory perception.  Neuropsychologia 18:321-330.

Sidtis, J. J. (1981).  The complex tone test: Implications for the
assessment of auditory laterality effects.  Neuropsychologia 19:103-112.

Cheers,
Bob.

Robert S. Bolia
Air Force Research Laboratory (AFRL/HECP)
2255 H Street
Wright-Patterson Air Force Base, OH 45433-7022
Phone: (937) 255-8802
FAX: (937) 255-8752
URL: www.geocities.com/rbolia


> From: Mitchell Sommers <msommers@ARTSCI.WUSTL.EDU>
> Reply-To: Mitchell Sommers <msommers@ARTSCI.WUSTL.EDU>
> To: AUDITORY@LISTS.MCGILL.CA
> Subject: Interesting dichotic effect
> Date: Wed, 24 Jan 2001 13:41:00 -0600
>
> I wonder if anyone has any thoughts or knows of relevant research for the
> following phenomenon.  In the course of calibrating headphones for a
> dichotic listening task, we generated stimuli consisting of two pure tones.
>  The stimuli were presented as follows.  Stimulus 1 presented to the right
> ear had equal-amplitude tones at 100 and 150 Hz.  Stimulus 2 presented to
> the left ear had equal-amplitude tones (same amplitude as in stimulus 1) of
> 200 and 250 Hz.    Stimuli 3 and 4 were simply the reverse of these two (
> left ear gets 100 and 150; right ear gets 200 and 250).  The rationale
> behind playing with these stimuli was that "perfect" integration across the
> two ears should produce the identical percept for both pairs of tones.
> That is, stimuli 1 and 2 presented dichotically, should sound identical to
> stimuli 3 and 4 presented dichotically because the spectral content is the
> same, we just switched the ear to which each was presented.  Instead, the
> perceptual experience was a change in pitch.  Interestingly of 4 listeners
> 2 perceived a decrease in pitch and 2 perceived an increase (i.e., when 3
> and 4 were presented dichotically after hearing 1 and 2, there was either a
> decrease or increase in pitch).  We then tried simply reversing the
> headphones (left transducer on right ear and vice-versa) and the perception
> was the same.  We also tried a different combination such that stimulus 1
> had equal-amplitude components at 100 and 400 Hz and stimulus 2 had equal
> amplitude components at 200 and 300 Hz.  Again, the perception was a pitch
> change when we switched channels for stimulus 1 and 2.   I'd be interested
> in any ideas as to why we would get a clear pitch change using this
> stimulus configuration.  Many thanks
>
> Mitch Sommers
>
>
>
> Mitchell S. Sommers, Ph.D.
> Associate Professor
> Department of Psychology
> Washington University
> Campus Box 1125
> St. Louis, MO 63130
>
> E-mail: msommers@artsci.wustl.edu
> Phone: 314-935-6561
> Fax::  314-935-7588
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