The human brain is a storehouse of countless sounds and sights, which get stored into a database which the mind recalls whenever it encounters any of them.
Collections of neurons in brain have their own ways to efficiently encode sound properties that are predictable.
"In perception, whether visual or auditory, sensory input has a lot of structure to it. Your brain takes advantage of the fact that the world is predictable, and pays less attention to parts it can predict," said Keith Kluender, a psychology professor at the University of Wisconsin-Madison.
The study showed that listeners become effectively deaf to sounds that do not conform to their brains' expectations. Listeners completed trials where they were asked to identify one sound in a set of three that was unlike the other two.
Distinguishing sounds that varied in instrument and onset in the same way they had just heard was a simple matter. But sounds that didn't fit - with, say, more pluck and not enough saxophone - were completely lost to the listeners. They could not correctly identify one of the non-conforming sounds as the odd one among three examples.
"If you have an efficient system, you should take advantage of that in the way you perceive the world around you. That's never been demonstrated this clearly with people," said graduate student Christian Stilp.
To avoid having to carefully take in and remember every last bit of visual or audible stimulus it encounters, the mind quickly acquaints itself with the world's predictability and redundancy.
The study is published in this week's (Nov. 22) early online edition of the Proceedings of the National Academy of Sciences.