Selective attention is the ability to concentrate on a specific flow of sound amid a babble of background noise, for example listening to a conversation in the middle of a crowd. In the diagram presented, the red particles represent items of sound information. All sound enters the ears and passes through a selective filter, which discards irrelevant information, then goes into a limited-capacity decision channel, which decides on the specific source of the sound. Both mechanisms probably operate below the level of consciousness. Some items pass into the memory store. Information from the decision channel and memory store determine which actions are taken by the brain.