“How can we look directly at things and not see them? The answer is that your brain perceives the world through what amounts to a mental ‘soda straw.’ When it aims that straw at one thing, all other objects—even those within your direct field of vision—recede into the background. Cognitive psychologists call this phenomenon selective attention, a neural process by which the ‘volume knob’ on one set of sensory inputs is turned up at the same time the intensity settings of all other stimuli are turned down.”