Passport officers compared photos to people, trying to spot the mismatches. In this case, the photo is genuine. (David White -- CC BY SA)

If you've been lucky enough to enjoy a vacation this summer, you've most likely handed your photo ID over to a TSA agent (or your own country's equivalent). But according to a study published Monday in PLOS ONE, endless practice hasn't turned them into human passport-scanning machines. In fact, the people responsible for checking photo identification all day might not be any better at recognizing a mismatched face than you are.

In the study, 49 passport officers from the Sydney Passport Office were tested on their face-matching abilities. Many were highly experienced, with an average of over eight years among them, and all but three had undergone a special training course on face recognition (which told them, for example, to break the face down into individual features and compare each one).

When the officers compared photos to live people, they let fraudulent photos through 14 percent of the time. When asked to decide if multiple photos truly showed one person at different ages (an important skill, since many photo IDs are good for as long as a decade), the officers showed a similar error rate and didn't perform any better than student volunteers given the same task. The researchers also gave the officers the Glasgow Face Matching Test, a standard test of face matching ability. Here, the researchers were able to compare the final scores to those expected in the general population -- and on average, the officers just weren't any better at matching faces.

A few officers did quite well, and some even had perfect accuracy. But when the results were broken down, the researchers didn't find any correlation between work experience and matching accuracy. In other words, it seems to be more of an inherent knack than a learned skill.

Facial recognition is easier for some than others, and there's a broad range of ability. Many people don't even realize they have some degree of "face blindness" until they read a description of the neurological quirk, and others (myself included!) have notable difficulties with facial memory. But the idea that the agent checking passports might be unable to tell people apart is a bit worrisome. In response to this particular study, the Australian Passport Office now uses facial matching tests during its staff recruitment process.