While focused research is vital it can also unintentionally lead to what is called “inattentional blindness,” that is, looking without seeing. In other words, if you are looking for one thing–one name, for example–you might miss other things.
Take a look at the following video:
Are you guilty of this when researching?
When you are searching tax lists or census records, do you focus tightly on certain names or surnames? Or do you search with your eyes open, noticing what else is happening in the records? You might be surprised at what you see in the records when you simply pay attention.
 David McRaney, “Inattentional Blindness,” in You Are Not So Smart: A Celebration of Self-Delusion blog, posted 1 October 2009 (http://youarenotsosmart.com/ : accessed 21 Nov 2011).