November 21, 2018
Let’s face it: Most of us have no problem recognizing somebody whom we have seen before. Remembering where we met (or saw) him or her, and putting a name to those familiar features requires a different set of skills altogether.
Throughout our lives, we commit faces to memory, according to a November 20 report by Psychology Today. We can recall classmates from elementary school, people who share our morning commute, and the actors in our favorite television shows. But how many of those faces are stashed in a permanent mental repository?
Researchers at the University of York in the United Kingdom recently sought to pin down that number—estimating that people know an average of 5,000 faces. And that figure simply represents the number of faces we might know—not the number we are capable of retaining, according to their findings, published in the Proceedings of the Royal Society B.
“We may not have an upper limit for face learning,” Rob Jenkins, the lead author of the study, told Psychology Today, adding, “The thousands of faces we commit to memory may only be the tip of the iceberg for this mental capacity.”
Jenkins and his colleagues asked 25 participants, between 18 and 61 years old, to list the people whose faces they would recognize. The researchers helped by providing prompts to consider specific social niches, such as colleagues, friends of family, and retail staff. Participants also listed every famous figure they could recall and recognize.
Next, the investigators presented a slide show of famous figures and calculated the ratio of how many faces participants said they recalled to how many they were able to recognize from the photo series. (They couldn’t do the same for non-famous faces, since it wasn’t feasible to collect photos of them.) Applying that ratio to participants’ lists of people they would recognize allowed the researchers to arrive at a final estimate.
The team found that recognition abilities differed greatly among participants—ranging from a “low” of 1,000 to as many as 10,000 familiar faces. That variation may be due in part to the environment in which someone was raised—a rural or urban area, for example—as well as their level of media exposure, Jenkins speculates.
They concluded that, as humans gradually have transitioned from living in small, tight-knit communities to a large, interconnected world, the ability for facial learning has been up to the task. “It seems that if you’re building cognitive equipment that allows you to differentiate between a couple of hundred individuals, in doing that you’re building apparatus that’s also good for several thousand,” Jenkins told the magazine. “Maybe you can’t achieve the former aim without incidentally gaining the additional capacity we use now.”
Indeed, retaining facial recognition over time requires observing and internalizing the same visage with various expressions, at different ages, and in assorted contexts. A face can look different when its owner puts on makeup, gets a haircut, ages five years, or appears in a darkened restaurant rather than a brightly lit room, Psychology Today reported.
“The key to learning each face is learning the person’s variability,” Jenkins says. “You have to be exposed to the way the face changes.” (One key factor is that people generally tend to be poor at remembering faces they have encountered only briefly, he says. That deficit becomes exceedingly important in legal or forensic situations, such as during eyewitness testimony.)
Identifying how many faces people recognize—and how those faces become familiar—is relevant for understanding deficits of face perception, Wilma Bainbridge, a post-doctoral researcher at the National Institute of Mental Health who studies the perception and memorability of images, said in an interview with the magazine. For example, she suggests, face vocabulary could potentially be used as a marker of perceptual decline in the course of Alzheimer’s disease.
The brain also possesses a strong capacity for object memory, yet evidence suggests that faces require a unique form of processing, Bainbridge says. Humans are drawn to the geometry of faces from an early age: A 2015 study conducted at the University of Padova in Italy found that infants show a preference for an image of two dots above a third (which more closely mimics a face) compared to two dots below a third.
Finally, faces that embody more emotion or threat are especially enduring, Bainbridge says. “It may be less important to know a familiar or unfamiliar place, because you can take time to explore,” she notes, “But it could be really important to pick out your friends and your enemies.”
Research contact: firstname.lastname@example.org