|MadSci Network: Neuroscience|
Great question! It is possible for your brain to "ignore" information that it is receiving. An example of this is what is termed, "the cocktail party effect." The following information is taken from a paper written by Barry Arons who works at the Massachussets' Institute of Technology Media Lab. The paper is available on-line at: http://xenia.media.mit.edu/~barons/cocktail.html "The ``cocktail party effect''--the ability to focus one's listening attention on a single talker among a cacophony of conversations and background noise--has been recognized for some time. This specialized listening ability may be because of characteristics of the human speech production system, the auditory system, or high-level perceptual and language processing." Dr. Arons describes a series of experiments in which "Subjects...listened to different spoken messages presented to each ear with headphones. In this configuration there is no directionality, there is simply a dichotic signal. The subjects had no difficulty in listening to the message played to one ear while rejecting sounds in the other ear. The recognition process can easily be switched to either ear at will. The subject could readily shadow one message while listening, though with a slight delay. ... Note that the subject's voice is usually monotonic and they typically have little idea of the content of the message in the attended to ear. Virtually nothing can be recalled about the message content presented to the other (rejected) ear, except that sounds were occurring." Dr. Arons states, "This is what might be called the ``what-did-you-say'' phenomenon. Often when someone to whom you were not ``listening'' asks you a question, your first reaction is to say, ``uh, what did you say?'' But then, before the question is repeated, you can dredge it up yourself from memory. When this experiment was actually tried in my laboratory, the results agreed with our intuitions: there is a temporary memory for items to which we are not attending, but as Cherry, James, and Moray point out, no long-term memory." In response to your last two questions, it is my guess that it is quite common for humans to be able to "shun their hearing".
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