Airport security unlikely to spot many weapons

"When airport screeners don’t expect to find a gun in your bag, they likely won’t, suggests new research that shows that when people think something will be difficult to find, they don't look as hard as when they think they're likely to see what they're searching for.

Call it the needle-in-the-haystack effect: Humans aren’t adapted to finding rare things.

"We know that if you don't find it often, you often don't find it," said cognitive scientist Jeremy Wolfe of Harvard Medical School. "Rare stuff gets missed."