C&B Notes

The ‘Cocktail Party Effect’

We have previously shared a piece on how humans balance awareness and attention, and a group of California-based scientists now believe the brain has a base level function that forces us to focus on one stream of sound at a time.  It has interesting implications for how effective multitasking is and whether we can even multitask at all:

This ability to hyper-focus on one stream of sound amid a cacophony of others is what researchers call the “cocktail-party effect.”  Now, scientists at the University of California in San Francisco have pinpointed where that sound-editing process occurs in the brain — in the auditory cortex just behind the ear, not in areas of higher thought. The auditory cortex boosts some sounds and turns down others so that when the signal reaches the higher brain, “it’s as if only one person was speaking alone,” says principle investigator Edward Chang.

These findings, published in the journal Nature last week, underscore why people aren’t very good at multitasking— our brains are wired for “selective attention” and can focus on only one thing at a time.  That innate ability has helped humans survive in a world buzzing with visual and auditory stimulation.  But we keep trying to push the limits with multitasking, sometimes with tragic consequences.  Drivers talking on cellphones, for example, are four times as likely to get into traffic accidents as those who aren’t.

Many of those accidents are due to “inattentional blindness,” in which people can, in effect, turn a blind eye to things they aren’t focusing on.  Images land on our retinas and are either boosted or played down in the visual cortex before being passed to the brain, just as the auditory cortex filters sounds, as shown in the Nature study last week.  “It’s a push-pull relationship — the more we focus on one thing, the less we can focus on others,” says Diane M. Beck, an associate professor of psychology at the University of Illinois.

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