In the classic movie Casablanca, Humphrey Bogart’s character never says “Play it again, Sam.” Really. Look it up. What Bogey’s American expatriate, Rick Blaine, really said is "If she can stand it, I can. Play it." The latter may be correct, but the former sounds better to our ears and therefore has been repeated in our society until it sounds right.
The human brain’s penchant for order and consonance is also to blame, so it is not uncommon for famous quotes such as these to get tweaked over time. The information superhighway doesn’t discriminate; incorrect information can travel just as far and as fast as the truth on the Internet. Oft quoted sources like Shakespeare, Mark Twain, political figures, books, songs and countless movies all fall victim to our collective selective memories.
So, why do misquotes become real quotes when released into the wild? How can we help ourselves from perpetuating something someone never said or wrote?
Maria Konnikova, psychologist and journalist whose first book, Mastermind: How to Think Like Sherlock Holmes, will be published by Viking in January 2013; writes the "Literally Psyched" column for Scientific American; her writing has appeared in The Atlantic, Slate, The Paris Review, The Observer, Scientific American MIND, and Scientific American