Scientists think they've found the reason that overhearing cell phone conversations makes the average person's blood boil. It's because hearing half of a conversation takes more concentration and attention than hearing both sides of a talk, say Cornell University researchers.

According to this Reuters story, hearing half of a story is more difficult to tune out than a whole story. So if you ever wondered why you're so irked that you're hearing some guy on the bus gripe about a bad date, it's probably because you're trying to fill in the gaps for yourself (and you're also guessing incorrectly).

With Americans spending more than 2 trillion minutes on cell phones last year, according to the wireless trade association CTIA, there are infinitely more chances to get caught up in half of a conversation that you wouldn't want to hear given the choice.

The Cornell scientists did research with students that involved concentration exercises. Students made more errors guessing how a conversation would go when they heard just one side.