Re: Instruction for subjects

[Bruno Repp <repp@xxxxxxxxxxxxxxxx>]

Dear Fatima:

I found your observations interesting, although I am not really an 
expert on this phenomenon. Nevertheless, the task reminds me of some 
work on phoneme restoration that I did long ago.

I suspect that the reported continuity of the disrupted/masked sound 
is not really auditory, or only partially so. Rather, it is a figural 
completion achieved at a higher level of processing. It may be 
analogous to the completition of partially hidden objects in vision. 
If part of an object is obscured by another object, people don't 
really "see" the obscured part, even though they perceive the 
obscured object to be intact. Similarly, the disrupted/masked sound 
may be perceived as a continuous auditory "object", even though 
people really don't "hear" it during the masked portion.

You are asking your subjects to compare a sound which is heard in its 
entirety to one that is heard only partially, and that may be the 
reason for the confusion. The empirical question is what is actually 
heard during the /disrupted/masked segment: Do people only hear the 
masking noise, or do they also hear the masked sound? You could try 
to address that question by asking subjects to compare the disrupted 
test sounds with standards that have their central segment attenuated 
by varying degrees. Perhaps there is a certain degree of attenuation 
that best matches what subjects actually hear.

Best,

Bruno

> Dear List
>
> I am running some pilot behavioral studies of auditory continuity illusion
> (aka temporal induction).
> The sounds are FM sweeps with gaps or noise-inserted gaps.
> For various reasons I am running them as "same/different" trials, 
> wth the first sound of the trial being a regular FM sweep and the 
> second one being
> the modified FM sweep.
>
> When I ask the subjects, "Is the second sound as continuous as the 
> first sound?" they become confused.
>
> Even FM sweeps with much-louder noise inserted in the gap are 
> considered by some subjects to be not very continuous. (contrary to 
> literature)
>
> How do I change my instructions (basically, the confusion is around the
> word 'continuous')? Or change the task?
>
> Any ideas?
>
> Thanks
>
> Fatima T. Husain, Ph.D.
> NIDCD/NIH
> Bldg. 10/ Room 8S-235D
> Phone: 301-594-7758


--
Bruno H. Repp
Haskins Laboratories
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Fax (203) 865-8963

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