The brain is an amazing mechanism.
Youre at a crowded do with lots of noise, the band is playing and the noise level keeps going up with each round of drinks. Been there? Youre surrounded by noise. Youre swimming in it. Yet, you can focus on a single voice asking you to Please pass the pigs in a blanket. Just cant get enough of them. So, how are you able to single out this gourmets request for hot dogs in dough? And still not miss a beat in the conversation youre having with your spouse?
You hear in stereo. Because the ears at set apart from each other, sound waves reach each ear at slightly different times. This difference in sound recognition between ears is what enables us to determine the direction of the sound, also known as directionality.
While walking through the quiet woods, you can pinpoint the location of a birds call with real accuracy. Each ear receives the birds call at a slightly different time (were talking nanoseconds here, folks). The signals processed within the auditory system ear, ear canal, tympanic membrane and the other bits within the ear reach the brain a split second apart.
The brain, through experience, is able to calculate the direction of the sound instantly. Its a throwback to the days when our ancestors were squatting in caves and saber-toothed tiger attacks could take place on your way to work if your hearing mechanism couldnt determine the direction of potential danger (a twig snap), giving you enough time to run away.
But wait. If the ability to focus on a single voice within the din of cocktail party clatter is based on our ability to determine sources of sound within the room, how do we explain the ability to focus on a telephone call while the party is in full swing. If the phone rings, you can still carry on a normal conversation even though youre surrounded by sounds coming at you from virtually all directions including those sound waves that bounce of the ceilings and walls. Room tone.
Now obviously, you cant determine the direction of the speaker on the other end of a telephone line because shes not even in the room. So something else must be going on.
Research in laboratories around the world has led to a different view of how humans sort sounds, not by directionality, but by priority. Researchers now suggest that were able to maintain focus on our little group, or quiet conversation by differentiating sound by pitch. The brain focuses on the pitch the sound quality of important conversations while dismissing party background noise as unimportant. These sounds, while heard and processed, dont take on importance within the hearing portion of the brain a place called the auditory cortex located on the temporal lobe of the brain.
Dr. Holger Schulze, a neuroscientist at the Leibniz-Institute for Neurobiology in Germany, and a lead researcher on the phenomenon of cocktail party ear, stated in an interview, We think this is a major way the brain can do this cocktail party phenomenon.
It has been known for 20 or 30 years that it is possible without directional information to do the job [focus on a single conversation while blocking out unnecessary noise], Dr. Schulze explained, but we didnt know how it [the process] works, where in the brain this happens. Now we know its in one small area of the auditory cortex. FYI, the auditory cortex is where electrical impulses produced by sound in the environment are processed by the brain.
Researchers now believe that different noises and voices are arranged in a circle in the auditory cortex.
Within a circular map you can connect each region with all other regions equally well," Schulze told LiveScience. "This is important if you want one region to be able to inhibit all other regions equally well. If it [the sound-sorting process] was linear, you could only inhibit your neighbors."
So how do these researchers explain the pigs in a blanket phenomenon that is such a central part of concentration? "One area sends neurotransmitters to other areas to say, 'Stop listening,'" Schulze said. "But there must be some residual activity left so that if you hear something that catches your attention you can selectively switch focus."
In other words, the brain prioritizes all of these different sounds, focusing your best party smile on the individual with whom youre speaking while ignoring the less important noise, or at least relegating it in importance. However, a small portion of the brain keeps track of important incoming sounds so when the guy asks for his pigs-in-a-blanket, one part of your auditory cortex can process that request (and, thus, you pass the platter and smile) while maintaining primary focus on the person with whom you were and are conversing.
Extraneous sounds receive the lowest priority. So, if youre engaged in an important business discussion at the convention and the band starts up, you can selectively block out noise by assigning different pitches different levels of priority. So you can focus on the speaker intently, pass the silver platter of appetizers and block out Grand Funk playing loudly on the stereo. (Its an older crowd.)
Though we can distinguish individual voices without knowing where they are coming from, if we have directional information this process is even easier. Both the pitch-sorting mechanism and directional sorting are usually going on simultaneously, Schulze concluded.
Interesting stuff. Make a mental note to hear your brain at work, sorting and prioritizing whats important sound information and what can be ignored and blocked out.
Now, would you pass the shrimp puffs this way? Thanks so much.