From www.psychologicalscience.org - January 17, 2012 4:06 PM

Tackling a crossword can crowd the tip of your tongue. You know that you know the answers to 3 Down and 5 Across, but the words just won’t come out. Then, when you’ve given up and moved on to another clue, comes blessed relief. The elusive answer suddenly occurs to you, crystal clear.
The processes leading to that flash of insight can illuminate many of the mind’s curious characteristics. Crosswords can reflect the nature of intuition, hint at the way we retrieve words from our memory and reveal a surprising connection between puzzle-solving and our ability to recognize a human face.