According to Science News, new findings from a longitudinal study following kids since 1976 revealed some surprising results. Here is the basic study set up according to the authors
Over two years, Montreal students in grades 1, 4 and 7 completed peer evaluations of their classmates and rated them in terms of aggression, likeability and social withdrawal. The students also did self-evaluations
We found the evaluations from the group of peers were much more closely associated with eventual adult outcomes than were their own personality perceptions from childhood.
These findings tie nicely in with the research Bailey Norwood and I have conducted over the past several years (see here, here, or here), where we argue (and find) that the best way to predict what someone will do in the grocery store is often not to ask them what they will do but rather to ask them what they think someone else will do.
The human mind is skilled in the art of deception (including self deception). This research reminds me of a quote by Richard Feynman:
The first principle is that you must not fool yourself—and you are the easiest person to fool.