Re: Interesting dichotic effect (Al Bregman )

Subject: Re: Interesting dichotic effect
From:    Al Bregman  <bregman(at)HEBB.PSYCH.MCGILL.CA>
Date:    Wed, 24 Jan 2001 16:15:47 -0500

Mitch, Do you think that this phenomenon is related to "diplacusis", the fact that the same stimulus can have a different pitch (typically a small difference) at the two ears? Were your pitch differences large or small? Can you estimate it in semitones? You say some subjects heard an increase, and others a decrease in pitch. Did the same subjects hear the same differences in Stimuli 3 and 4, as they did in stimuli 1 and 2? In other words, was the difference in subjects a stable difference. Al ------------------------------------------------------------ Albert S. Bregman, Emeritus Professor Psychology Dept., McGill University 1205 Docteur Penfield Avenue Montreal, QC, CANADA H3A 1B1 Office: Tel: +1 (514) 398-6103 Fax:+1 (514) 398-4986 Home: Fax & phone: +1 (514) 484-2592 Lab web page: ----- Original Message ----- From: Mitchell Sommers <msommers(at)ARTSCI.WUSTL.EDU> To: <AUDITORY(at)LISTS.MCGILL.CA> Sent: Wednesday, January 24, 2001 2:41 PM Subject: Interesting dichotic effect 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(at) Phone: 314-935-6561 Fax:: 314-935-7588

This message came from the mail archive
maintained by:
DAn Ellis <>
Electrical Engineering Dept., Columbia University