According to Social Triggers and Wired Magazine, George Lowenstien, a professor at Carnegie Mellon University developed a theory called “the information gap theory of curiosity.”
Lowenstein says “curiosity is rather simple: It comes when we feel a gap ‘between what we know and what we want to know.’” (source)
He goes on to say “This gap has emotional consequences: it feels like a mental itch, a mosquito bite on the brain. We seek out new knowledge because we that’s how we scratch the itch.”
That’s why these headline formulas increase traffic.