Target fixation is generally thought of as a military term for one who is so focused on that one target or making the shot – that they lose sight of the other hazards. Many credit the terms origins back to World War II where fighter pilots on strafing runs would fly into the target as they were so fixated on it or remark on another close call. In the Building Science field, I liken this to those so set in a notion or idea that they forget all the other factors that come into play. For more on the history of it: Scroll approx 1/2 way down to “history” section