It’s happened to all of us – you hear a song that you don’t want to like. You try to resist, but you can’t. By the end of the song, you’re tapping your foot and singing along. Why are some songs so irresistibly catchy? Karen used to think it was magic. But when she looked closer, she had an epiphany – it’s actually just math. Songs are catchy because they’re scientifically engineered to be that way. Karen shows you how. Filmed at Ignite Seattle 12 12-07-2011.