Subject: Re: By any other name... From: Valeriy Shafiro <Valeriy_Shafiro@xxxxxxxx> Date: Thu, 22 Mar 2007 14:27:24 -0500 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>So, when a tree falls in the forest, with a helicopter is flying over your head, does the tree ... It seems that the answer to the question of whether the signal is present or absent when it is replaced by noise will depend on our level of analysis. As far as we can trust signal processing methods for 'objective' judgments, it seems that different signal processing methods may classify a signal as either present or absent as well. Also, I recall that the ability to judge the signal as being replaced vs masked by noise was used to study the strength of restoration by Samuel, 1981. (Not that there isn't a psychological trick for the investigator studying this phenomenon as well). On the other hand, knowing under what conditions the signal (or rather associated percept) is reported as being present can tell us something about the analysis process, making the metaphysical aspects of 'objective' reality of the signal somewhat irrelevant. For example, we did a small experiment (sorry for self promotion) that seemed to indicated that the same element of an acoustic signal (i.e. white noise) can be perceived as either hiding fricative noise of speech or as nonspeech noise depending on whether it is integrated with the speech or noise components of a mixed signal. Since it was always the same acoustic segment (which was not speech per se), the objective reality of it seemed less relevant than the perceptual one. (The details of the study can be found here: http://dx.doi.org/10.1007/s10936-007-9054-y ) Valeriy ------------------------------------------------------------- Valeriy Shafiro Communication Disorders and Sciences Rush University Medical Center Chicago, IL office (312) 942 - 3298 lab (312) 942 - 3316 email: valeriy_shafiro@xxxxxxxx -----AUDITORY - Research in Auditory Perception <AUDITORY@xxxxxxxx> wrote: ----- To: AUDITORY@xxxxxxxx From: Bruno Repp <repp@xxxxxxxx> Sent by: AUDITORY - Research in Auditory Perception <AUDITORY@xxxxxxxx> Date: 03/22/2007 12:38PM Subject: Re: By any other name... Thanks, Dan, Daniel, and Yoshitaka, for your excellent comments. I agree with you, of course, yet there is still something that bothers me. If it does not really matter whether a signal is present or absent, why do researchers make the effort to put a gap in the signal? Why not just mask a continuous signal instead? If the masker is strong enough, it should not matter. However, the finding of perceived continuity will seem much LESS SURPRISING when the signal was actually present than when it was absent. So, the actual introduction of a signal absence seems like a psychological trick on the part of the investigator. This does not apply, of course, in cases like the one described by Yoshitaka, where some percept is synthesized out of nothing, as it were. --Bruno >On 3/22/07, Bruno Repp <repp@xxxxxxxx> wrote: >>If objective methods cannot prove the absence of the signal, >>then I would argue that the signal is in fact present. Is an >>objective proof of signal absence typically presented in studies of >>the auditory continuity effect? > >I don't think the objective presence or absence is very interesting; there >is a range of circumstances in which a more optimally configured >detector might be able to detect the absence of a perceptually restored >tone (although those circumstances may be surprisingly narrow). > >What is more interesting is that even in genuinely undecidable circumstances, >when, as Yokashita puts it, the signal is objectively "either present >or absent", >the perceptual system does not report that ambiguity but instead returns a >confident answer. Moreover, in the case of continuity, that answer is not the >locally simplest answer (no spectral peaks = no perceived tones), but instead >is the "simplest" answer on a much broader scale (continuous tone more likely >than tone with a gap synchronized with noise burst). > >Maybe the objection is that *of course* the perceptual system will do the >reasonable thing of assuming continuity when there is no counter-evidence. >But the computational implementation of a system that can capture and >apply this kind of definition of "reasonableness" is much more complex than >a lay person might expect from the auditory system - and a majore challenge >for those of us interested in modeling perceptual sound analysis. > >>If objective methods cannot prove the absence of the signal, >>then I would argue that the signal is in fact present. > >This reminds me of the discussion we had a few years ago about the >WW2 aircrews who could conjure up the illusory experience of listening >to favorite pieces of music in among the earsplitting drone of the aircraft >engines during long missions. Since no objective measure can distinguish >the presence or absence of Beethoven's 5th at 20 dB below the air conditioning >noise in my office, why am I not perceiving it (or only that one, and not the >infinity of other unmeasurably-quiet signals that are also "present")? > > DAn. -- Bruno H. Repp Haskins Laboratories 300 George Street New Haven, CT 06511-6624 Tel. (203) 865-6163, ext. 236 Fax (203) 865-8963 http://www.haskins.yale.edu/staff/repp.html NOTE: I am at Rutgers University, Newark, two days each week, usually Wednesday and Friday, and don't read my Haskins e-mail on those days. To reach me at Rutgers, send e-mail to <repp@xxxxxxxx>.