[FIND] Science: Our Eyes Miss What's Rare

Julianne Greenberg spends most days staring at images of women's breasts. She's a radiologist, and it's her job to search hundreds of X-rays every day for signs of breast cancer.

She admits, she's looking for a needle in a haystack.

In that, she's a lot like airport baggage screeners scanning thousands of suitcases a day for what's incredibly rare - weapons, bombs, or anything else that could threaten the safety of airline passengers.

On NPR's All Things Considered, Alix Spiegel reported yesterday on recent studies that looked into how the brain works when performing visual searches for something rare or difficult to see - such as breast cancer amongst thousands of healthy breasts, or a gun inside one single piece of luggage.

As for whether trained experts in the real world can overcome this "prevalence effect" (i.e. people's tendency to miss anything rare), scientists are still investigating. Meanwhile, as reporter Spiegel concludes, we'd all best be realistic about the imperfections of the human brain and, as PIs, our ability to spot a subject's generic black SUV every time after six hours of watching a busy street full of similar vehicles.

Hear the story (or read a transcript) here at NPR's website, where you can also take a quick test to find out how well you notice small changes in a visual landscape.