Oddly Wired
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attention

You miss the obvious when your focus is occupied.

Participants often fail to notice a prominent stimulus, like a person in a costume, when they are engaged in a simple counting task.

Inattentional blindness reveals that perception is not a passive process of 'seeing' what is in front of you. The brain prioritizes specific tasks so aggressively that it essentially filters out anything outside that narrow goal.

You see exactly what you are looking for.

Where this comes from

Study
Simons and Chabris, 1999
What the check found
The reference confirms the authors and the experiment, though it does not detail the specific methodology of the counting task or the costume stimulus.
Confidence
Solid, with limits

Related

One of these every day, and every one names the study it came from. When a finding is contested, it says so.