I think I first heard the rule: your first answer is almost always correct, from GMM1 Giles when I was in Gunner’s Mate “A” School at Great Lakes Naval Training Center in Illinois.
I’ve repeated the rule, without question, dozens of times to my students over the years.
I was wrong.
From Mano Singham:
A book given to people taking the GRE exam advises them that “Exercise great caution if you decide to change an answer. Experience indicates that many students who change answers change to the wrong answer.”
This advice represents a widespread belief that our instincts, our intuitive senses, are the most reliable guides to decisions. It is based on the assumption that instincts are based on prior knowledge and experiences and that our brains integrate all these things to enable us to make quick judgments that tend to be sound. This is the idea heavily promoted by Malcolm Gladwell in his book Blink.
But is it true?
I was interested in this study (published in the Journal of Personality and Social Psychology, 2005, Vol. 88, No. 5, 725–735 by Justin Kruger, Derrick Wirtz, and Dale T. Miller) titled “Counterfactual Thinking and the First Instinct Fallacy” (subscription required but you can see a fairly detailed discussion of the paper here) that examined the answers given by 1561 students in response to a multiple choice test. By looking at the erasures and comparing them with the final answer, they found that 51% changed their answers from wrong to right, 25% from right to wrong, and 23% from wrong to wrong. In other words, when people changed their minds, they were twice as likely to go from wrong to right as from right to wrong.
The finding underscore another rule: It is not that which we don’t know that can hurt us, it is that which we think we know that just isn’t so that will bite us on the ass.