Change/Inattentional Blindness

Change blindness is the experimentally demonstrated phenomenon in which a subject fails to notice a distinguishing feature or change when consecutively presented with two slightly different stimuli (e.g., words, illustrations or photographs). Change blindness occurs when stimuli are changed during saccadic eye movements, when changes are introduced to a stimulus display that flickers on and off, or when the stimulus is interrupted by a 'mask', for example a blank display or a 'mudsplash', consisting of small, high-contrast shapes temporarily 'splattered' over the image. Inattentional blindness is a related experimentally demonstrated phenomenon in which subjects fail to notice stimuli in their visual field because they are engaged in a task that requires attention to a different stimulus. For example, some subjects fail to notice a stimulus presented close to fixation because they are attending to a cross at fixation to discern which of its lines is longer. Inattentional blindness also occurs with complex and dynamic stimuli. In a popular experiment subjects fail to notice a man in a gorilla suit who walks through the action in the video they are watching. Similar effects can be produced in "real-world" situations, situations in which subjects interact directly with other people and not merely with video images. These results have been taken to show that there is no explicit conscious awareness of an item without attention, and that if it seems to us that we experience many items in our visual field simultaneously or in detail we are subject to an illusion. Both of these conclusions are contested.