Imagine that you are a bouncer, checking IDs outside a favorite bar in a college town. It is somewhat dark outside the door; there are many distractions: loud music is playing, and your job requires you to also keep an eye on the crowd for trouble.
Imagine that you are a bouncer, checking IDs outside a favorite bar in a college town. It is somewhat dark outside the door; there are many distractions: loud music is playing, and your job requires you to also keep an eye on the crowd for trouble. And because the patrons are dressed for a night out, many of them look somewhat different than their ID photos. Despite all these challenges, intuition probably tells you that matching faces to ID photos is smooth and accurate. Look at the picture, look at the person, and they either match or not. It turns out, however, that this intuition is wrong. Detecting false IDs is surprisingly tricky, primarily when they rarely occur. A bouncer for a college bar can likely expect to catch roughly a dozen fake IDs in the evening, and the cost for missing one is relatively low: an underage student sneaks into a bar, and the bar makes more money.
Now imagine that you are screening IDs for airport security. Again, you must simultaneously verify IDs while keeping an eye on the crowd for suspicious activity, and there is time pressure to hold the line moving. Moreover, travelers vary widely in age and appearance; their IDs and passports are from all around the world, and there can be significant differences between a person’s photo and their current appearance. Most importantly, only a scarce person would attempt to board an airplane with a false ID, and the consequences of missing that person could be dire. With the recent disappearance of Malaysian Airlines Flight 370 and reports that two men boarded the plane using stolen passports (although they were subsequently ruled out as potential terrorists), attention has become focused on this potential security loophole. In many airports around the world, there are several checks in place to prevent individuals with stolen IDs from passing through security, including scanning passengers’ passports against the Interpol database of known missing/stolen documents. Approximately 3.1 billion people traveled via airplane in 2013, yet Interpol estimates that passengers successfully boarded planes 1 billion times without having their passports scanned against their database. Although this oversight may reflect negligence or lack of available technology, it underscores the need to understand the second line of defense against stolen identity documents: the human ability to match faces to photographs. Given the myriad contexts in which society relies on face matching, it is surprising to learn that decades of research have documented its remarkable fallibility.
People often have the intuitive impression that they (and others) are “expert” face processors, given the social relevance and ubiquity of face and expression perception. In many domains, this intuition is correct. Humans are capable of recognizing hundreds of individuals across years, and under varying environmental conditions. However, this impressive ability is generally limited to familiar faces. In 2011, researchers asked U.K. and Dutch participants to sort 40 photographs of individuals into piles so that each pile contained pictures of the same person. The 40 photographs depicted only two individuals, both Dutch celebrities, and, in fact, almost all of the Dutch participants created only two piles. By contrast, the U.K. participants created an average of 7.5 separate piles. Without familiarity to aide their processing, the U.K. participants perceived the faces as representing far more unique identities.