Some tales are so tall that they trip over their own improbable feats, narrative cracks and melodrama. That one-on-one playground victory over Kobe Bryant back in the day; the 34 hours in labor without painkillers; the former girlfriend or boyfriend who spoke eight languages and was a secret agent besides.

Yes, uh-huh, really. Is it closing time yet?

Yet in milder doses, self-serving exaggeration can be nearly impossible to detect, experts say, and there are several explanations.

In that sense, fibs can reflect something close to the opposite of the frustration, insecurity and secretiveness that often fuel big lies. That may be why they can come so easily, add up so fast and for some people — especially around closing time — become indistinguishable from the truth.