Cocktail party effect

The cocktail party effect is a phenomenon wherein the brain focuses a person's attention on a particular stimulus, usually auditory. This focus excludes a range of other stimuli from conscious awareness, as when a partygoer follows a single conversation in a noisy room. This ability is widely distributed among humans, with most listeners more or less easily able to portion the totality of sound detected by the ears into distinct streams, and subsequently to decide which streams are most pertinent, excluding all or most others.

It has been proposed that a person's sensory memory subconsciously parses all stimuli and identifies discrete portions of these sensations according to their salience. This allows most people to tune effortlessly into a single voice while tuning out all others. The phenomenon is often described as a "selective attention" or "selective hearing". It may also describe a similar phenomenon that occurs when one may immediately detect words of importance originating from unattended stimuli, for instance hearing one's name among a wide range of auditory input.

A person who lacks the ability to segregate stimuli in this way is often said to display the cocktail party problem or cocktail party deafness. This may also be described as auditory processing disorder or King-Kopetzky syndrome.