Even the smallest change to someone's facial appearance, like wearing glasses, can shift our ability to identify them if we don't know them, according to a new study
This could have an impact as facial recognition, from software to passports, becomes a topic of interest for protecting identity.
Researchers at the University of York showed 59 study participants side-by-side images and asked them to determine whether each depicted the same person. The images included three categories: people wearing glasses, people not wearing glasses or an image of someone wearing glasses paired with one that wasn't.
Rather than showing them single images and asking for an identification to test their memory, the researchers wanted to test the participants' visual comparison abilities by presenting the side-by-sides. The participants were not under time constraints while viewing the images.
For cases in which both images showed someone in glasses or someone not wearing glasses, 80% of the students were able to accurately identify whether it was the same person. But that accuracy dropped 6% when comparing a person wearing glasses next to someone who wasn't.
"A 6% drop in performance may not sound like much, but if you consider the number of people who go through passport control at Atlanta International airport every year -- over 100 million last year -- a 6% drop in accuracy equates to 6 million misidentifications," said Kay Ritchie, co-author of the study from the University of York's psychology department. "We hope this work can be used to inform future policies on face identification, particularly given the discrepancy between different forms of photo ID when it comes to wearing glasses."
The researchers chose images of people who the participants wouldn't know or recognize. The images were also similar to what we're used to seeing on social media, including varied poses, facial expressions, lighting and background. Passport-style photos in which the pose or facial expression doesn't shift between images were not included.
All of the images were in color and high quality, loosely cropped around the head and found on Google Images. Researchers made sure that images of the same person didn't share backgrounds or angles or other comparable traits. To make things interesting, they also found similar-looking people, or "foils," and added them to the mix.
Based on the findings from previous work, the researchers knew that showing people different images of someone they're familiar with, like a family member, are instantly recognizable, even if those photos are over a passage of time.
"This robust ability to recognize familiar faces often leads us to incorrectly think we are good at recognizing all faces," Ritchie said. "Consider the passport controller whose job it is to look at a person's face and decide whether or not they are the person shown in the passport image. This is a difficult task because they are unfamiliar with the person, and the passport photo could be up to 10 years old."
As Ritchie pointed out, people are allowed to wear glasses in passport photos in the United States, but not the UK.
When we look at someone familiar, we "just know," Ritchie said. But when it comes to looking at an unfamiliar face, we focus on different things rather than assessing something identifying like their eyes or nose. It's the classical "first impressions" idea, said lead author Robin Kramer, a researcher in the University of York's psychology department.
"Some of the 'key' or fundamental trait dimensions may include attractiveness, trustworthiness and dominance," Kramer said.
Those in a class of "super recognizers," people like forensic examiners or those with higher natural abilities, tend to focus on the central region of the face, according to research cited in the study. But for most of us, it's a guessing game when it comes to unfamiliar faces.
"While we may still find it hard to believe that the inhabitants of Metropolis are unable to match Clark Kent with the numerous appearances of Superman in newspapers and on television, we can at least understand why Kent has chosen glasses as his aid to anonymity," the researchers said in their study.