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Re: perceptual segregation of sound
This note was intended to be sent to the entire list (my change of
e-mail address prevented it from appearing); Dan has replied to me privately.
What you've suggested so succinctly seems a lot like the concepts on
perception that I discuss on my Web site. Using a basic system
analysis approach I've tried to find fundamental principles from
which to establish generalized requirements for sensory systems based
on what it takes for animals to survive in their environments.
Here is some of my thinking: Survival requires an animal's sensory
organs to produce a timely response to environmental information.
These responses must identify the relative importance of sources in a
way that describes a "situation" whereby "awareness" characterizes
the auditory scene. In any situation, sensors should be able to
select for attention instantaneously the single most important source
within the scene. To do this the model I propose has a hierarchy of
perceptual levels each of which has its own ability for awareness and
attention but is subservient to judgments by higher authority. Each
level's responses are based upon specific time frames within which
information from each level can be made available. (Simple meanings
occupy less time to absorb than complicated meanings,) In addition,
each level is capable of selecting a priority source within its
domain for attention. For example, the lowest levels which have the
simplest information could respond reflexively to a source within
milliseconds. But its response could be moderated by a top-down
decision from higher levels. It is thus possible, as you suggest,
that what seems like simultaneous multiple-source attention at the
conscious level is actually the rapid switching of priorities among
source objects based on subliminal decisions at the lower levels. As
an example, consider the complexity of the attention decisions a
quarterback must process within the few seconds he has during a football play.
A crucial question: how to achieve and synchronize timely responses
at all levels. It appears to me that this problem has not been
seriously addressed in the current paradigm.
At 12:18 PM 4/28/06, you wrote:
I think another factor to consider in the concurrent segregation of
sounds is that much of the segregation may be accomplished
pre-attentively. Low-level (in the brain, and even cochlea) feature
detectors may segregate aspects of sounds, if not the sounds
themselves, well before they percolate up to what we call
"consciousness." This would depend on the type of segregating cue
under consideration, whether it is pitch, spatial location, onset time, etc.