[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: By any other name...
To me it the effect becomes more interesting when you consider the
contrast between filling in of gaps when interrupting noise is present
vs. not filling in of gaps when there is interrupting silence. By adding
noise, instead of silence, you haven't really given the brain any
additional information to enable the filling in, but nonetheless the
effect is there.
It reminds me of the work by Freyman et al. where speech reception
improves with the addition of advanced noise in a different spatial
location (relative to the target speech and a spatially coincident noise
masker), because of the precedence effect. The SNR as measured by a
microphone goes down, yet human performance goes up.
Although these two effects differ peripherally, I wonder if they can
somehow be linked at a higher (cognitive?) level.
Erik
Bruno Repp wrote:
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@xxxxxxxxxxxxxxxx> 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.
--
Erik Larsen
PhD candidate Speech and Hearing Bioscience and Technology
http://web.mit.edu/shbt
"Contrariwise," continued Tweedledee, "if it was so, it might be, and
if it were so, it would be; but as it isn't, it ain't. That's logic!"
-- Lewis Carroll, "Through the Looking Glass"