Anxiety leads to a narrowing of the field of attention, the so-called tunnel vision, and when people are anxious they are unable to attend to the total situation as is necessary to enable them to act rationally, but impulsively do the first thing that comes into their heads which is usually determined by what others are doing at the same time.

James A. C. Brown (1911-1964) Scottish psychiatrist, author [James Alexander Campbell Brown]

Techniques of Persuasion: From Propaganda to Brainwashing, ch. 9 (1963)