Mind & Body

The Average Person Can Recognize Thousands of Faces

Facial recognition technology is basically everywhere. Our phones can recognize us. So can Facebook, surveillance cameras, and who knows what else. Oddly, though, humans still don't quite understand our own capacity for recognizing and remembering faces. According to a new study, it's much more impressive than we realize.

The Face List

How many faces do you think you could recognize? On top of the faces of friends, family, co-workers, and other people you see in the flesh, there are countless others you see on the internet, TV, magazine racks, billboards, and advertisements. In a recent study, researchers from the University of York and the University of Aberdeen in the U.K. tried to estimate how many faces we have in our memory banks at a given time. They explored two basic questions: How many faces do people know personally, and how many famous faces do people recognize?

To answer the first question, the researchers had their 25 subjects simply spend an hour listing people whose faces they could mentally picture. To help them remember, the researchers provided 14 brainstorm categories, including "family," "friends of family," "own friends," "school," and "people met on a trip."

The listing process started off easy — Mom! Dad! Roommate! — but grew more and more challenging as the hour progressed. The team knew that because they automatically saved the participants' work every five minutes, which helped them analyze the rate at which they remembered. No one ran out of names entirely before the hour was up, though, so the researchers used the data to extrapolate when each person would likely have run out of names, and therefore how many names they probably would have remembered.

Next, they did roughly the same thing, but with famous faces. Here, the prompt categories were different — "film" and "fashion," for instance — but the process was roughly the same. People typically listed more faces from their personal life (about 400) than celebrity faces (about 300).

Still, memory is faulty. To get a sense of how their subjects' reported facial recognition abilities compared with their actual facial recognition abilities, the researchers prepared a database of more than 3,000 famous faces and asked study participants to indicate which ones they recognized. (It only counted as "recognition," for the study's purposes, if they recognized two separate photos of the same person.) This time, they lengthened the time limit considerably, asking participants to integrate it into their normal day-to-day routine over a period of three months.

It turned out that participants recognized roughly five faces for every one they recalled in that first test. Researchers used that ratio and the original names a person listed to extrapolate the total number of faces they knew.

What's Your Number?

Ultimately, the average study participant knew about 5,000 faces, and every study participant's number fell somewhere between 1,000 and 10,000. Keep in mind, though, that this is just the number of faces people actually know. In theory, they could remember more; our capacity for facial recognition is still uncharted territory.

Still, this is an interesting result. Historically, human communities have been limited to around 100 people, hardly big enough for a given person to ever meet thousands of people. Even now, in urban centers jammed with people, we build our own, smaller communities. According to previous research, a given person spends their time in just 25 places and can only maintain about 150 friendships at a time.

We can remember far more faces, however. As Dr. Rob Jenkins, a corresponding author of the study, explains, "The ability to distinguish different individuals is clearly important — it allows you to keep track of people's behaviour over time, and to modify your own behaviour accordingly."

In other words, if someone punches you, you have to remember their face, or you'll be vulnerable to them punching you again. Likewise, if someone does something nice for you, you'll want to remember their face so you can encourage future favors. Our ability to survive is linked to our ability to remember faces. Thank goodness we can remember thousands — maybe even more.

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The science of facial perception is more than skin deep. Learn all about it in "In Your Face: The New Science of Human Attraction" by David Perrett. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Mae Rice October 31, 2018

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