http://well.blogs.nytimes.com/2012/07/19/falling-into-the-diagnostic-trap/

For the doctors, this was a harrowing lesson in the trap of anchoring bias. It is so easy to slip into it without even knowing. But this case reminded us to keep reciting the mantra: if something doesn’t fit, don’t try to make it fit. Ask what else might be going on. Don’t fall into the trap.

(Wikipedia's article: http://en.wikipedia.org/wiki/Anchoring )