What causes words to get stuck on the tip of our tongue?

Ever had a word linger, infuriatingly, right on the tip of your tongue? Of course you have. We all have. The question is, what process happens in all of our brains that can block a word that's correct, while giving us a ton of options for words we know aren't correct? » 6/24/13 6:20am 6/24/13 6:20am