Research proposal ("Albert Bregman, Tel: 514-398-6103" )

Subject: Research proposal
From:    "Albert Bregman, Tel: 514-398-6103"  <IN09(at)MUSICB.MCGILL.CA>
Date:    Sun, 20 Sep 1992 19:55:50 EDT

September 20, 1992 Dear AUDITORY members: I am interested in doing a study on the relation between speech and primitive auditory organization. It is related to the claim by Al Liberman and some of his colleagues at Haskins laboratories that speech removes from the incoming acoustic data whatever it needs to form the words and then leaves the remainder to be heard as non-speech sounds. Let me describe the plan for the experiment, and then ask you some questions about it. THE PLAN: My idea for the study is to use sine-wave analog speech. This is speech in which each formant is replaced by a single sinusoidal tone whose frequency follows the same pattern over time as the formant did in the original speech. Such analogs can be heard as speech but this interpretation is not necessarily compelling. I plan to use two kinds of biasing with the subjects: Some subjects would be encouraged to hear them as speech, and others to hear them as "computer" sounds. Liberman's hypothesis would be that the subjects in the "speech" group would require more intensity to hear out one of the component tones. To summarize, then, there would be a form of biasing, followed by a test. Here are more details: (a) Biasing: Group 1 (Speech bias). The listeners are practiced on the analogs. Each is alternated with the word it mimics. Listeners rate the analogs on how easy they are to understand. Group 2. (Non-speech bias) The listeners are told that these "complex tones" are being considered as computer generated warning signals for the work-place and they are to rate them on some global qualities. e.g., how pleasant, smooth, or attention-getting they are. They are alternated with non- speech sounds for comparison. "Which one sounds smoother (or more pleasant, or more attention-getting)?" Listeners in this group would be given different degrees of exposure to the analogs to see whether familiarity alone had an effect on hearing the parts inside them. They would also get some sort of encouragement to hear them as coherent sounds (I haven't figured out how yet.) N.B. Group 2 can't simply be taught to hear the analogs as sets of whistles, because this training would make the tones audible for them at a lower level in the test, making it appear that Group 1's relatively worse performance (requiring greater intensity) was due to the fact that the interpretation as speech had made it harder for Group 1 to hear the tones. (b) Test procedure: On each trial, one of the analogs is alternated one of the tones that forms part of it. Subjects adjust the loudness of the tone inside the word until it can barely be heard. The outcome that would favor Liberman's position would be if Group 1 required greater intensity to hear the embedded sinusoid. MY QUESTIONS: Do you think that this is a fair test of the theory? Are the methods likely to work? Would the results be susceptible to other interpretations? Do you know of any facts that bear on how the results would come out? FINALLY: Do you think that the debugging of experiments or other projects beforehand is a good way to use the AUDITORY list? One wouldn't have to worry about others stealing one's ideas since the ideas would have been put forward in a public way on the list, associated with the name of the originator. Furthermore, it would be possible to avoid unnecessary duplication of efforts (people would tell you about similar studies in progress) and it might stimulate collaborations. What do you think? I would encourage people to answer to the list as a whole. - Al Bregman

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