Final answer:
The phenomenon where a person is temporarily unable to perceive a second target after recognizing a first one in quick succession is called Attentional Blink. It illustrates the cognitive limitations of our attentional processes and how selective attention can lead us to miss other stimuli. This is different from, but related to, Inattentional Blindness, which involves missing entirely visible objects due to focused attention elsewhere.
Step-by-step explanation:
The phenomenon described in the question is known as Attentional Blink. This occurs when a person, after recognizing a first target stimulus (such as a red letter), experiences a temporary impairment in their ability to detect a second target (the 'X') that appears closely in time after the first. This impairment happens because the brain requires time to fully process the initial stimulus, and during this time, the perception of the subsequent stimuli is reduced.
Attentional Blink demonstrates how our cognitive processing is limited and can only handle one task at a time efficiently when the tasks require rapid, focused attention. It's related to the way our nervous system functions, prioritizing certain tasks over others, and how selective attention can lead to missing other stimuli.
Other related phenomena include Inattentional Blindness, where we fail to notice visible objects because our attention is engaged elsewhere. An example of this is the famous study by Simons and Chabris where participants failed to notice a person in a gorilla costume because they were focused on counting basketball passes. Both attentional blink and inattentional blindness illustrate the intricacies of human perception and attention.