If you drive to pick up your child after school and notice that sometimes they go and greet听another parent听instead who has a car similar to yours, what goes through your head? This actually happened in a case that was reported in the scientific literature in听. The child鈥檚 name was Madison, and she would treat strangers like they were relatives while not showing the kind of affection toward her parents you would expect.
One day, Madison鈥檚 mom caught her approaching a stranger visiting their next-door neighbour. Madison thought the man听飞补蝉听their neighbour, even though the two men had different builds, heights, and ages. But both wore eyeglasses, and that鈥檚 what Madison had used to misidentify the man.
Experts were perplexed for years until Madison鈥檚 parents discovered the phrase 鈥渇ace blindness鈥� on the Internet.
Madison was in good company: primatologist Jane Goodall is also affected to a lesser degree, and yes that includes difficulty recognizing听chimps听by their faces. Famed neurologist Oliver Sacks wrote about Goodall for听听and confessed to his own face blindness, which he held responsible for his shyness.
The existence of face blindness prompts a provocative question: how can we tell disorders apart from normal variation?
Acquired vs. developmental face blindness
Human beings typically excel at recognizing faces, so much so that we start to see faces on Mars or Jesus鈥� mug on a toast because of a phenomenon we call pareidolia. Our brain is so good at identifying faces that it sees faces where they don鈥檛 exist.
Your average human can remember about听听and recognize one of these faces in a single glance lasting听. We used to think people scanned a face in a T-shaped pattern, paying close attention to the eyes and nose, but it turns out that we all have听听of examining faces with our eyes.
Except that some of us aren鈥檛 very good at it. The first modern study on face blindness was published in听, in the wake of World War II. Joachim Bodamer, a German psychiatrist and neurologist, described two soldiers who were injured during the war and who began to have difficulty recognizing faces afterwards. The soldiers had not noticed, but Bodamer did. He coined a term for this condition: prosopagnosia, from the Greek听prosopon听meaning 鈥渇ace鈥� and听agnosia听meaning 鈥渢he absence of knowledge.鈥�
This type of face blindness was acquired. It meant that you were fine until one day something happened to you that affected your ability to recognize faces (sometimes even your own in a mirror). It could be a stroke or a tumour or a head injury, and it creates a brain lesion, often on the right side of the brain, sometimes on both sides but rarely only on the left, that impairs your 鈥渇ace identity recognition鈥� pathway, as scientists refer to it.
But in听, Professor Helen McConachie described a stranger case. Known only by her initials A.B., the child was nearly 13 years old and was referred to a London hospital in part because she had never been able to recognize faces, except for those most familiar to her. Instead, she would identify people by their mannerisms and the clothes they wore. The problem is that A.B. had no trace of a head injury and she had always been like this. Her prosopagnosia was not听acquired; it 飞补蝉听developmental, and A.B. had found ways to compensate for it. 鈥淧erhaps,鈥� McConachie wrote, 鈥渢he condition is more common than is presently thought.鈥�
The definition of face blindness still has not been standardized, though it is classically defined as a lifelong face recognition impairment. The gaze of people with face blindness is often more dispersed as it scans someone鈥檚 face, looking at features like hair, maybe as a way to compensate. Many don鈥檛 even realize they have it, and often parents or teachers will spot it in a child based on their behaviour. Recognizing the faces of close friends and learning new faces takes longer. A sibling who changed their hairstyle will suddenly appear as a stranger; meanwhile, strangers will be confused with familiar people. The key to face blindness is that familiarity becomes unreliable. This is different from Capgras delusion, where the faces of relatives and friends are still recognized, but the person with the delusion believes they have been replaced by identical impostors.
Studying face blindness has not been easy and experts in the field still do not agree on basic elements of this phenomenon, starting with how common it is.
Still in the Stone Age
If you read up on face blindness, you will see a staggering figure mentioned everywhere: that 2 to 3% of the population has it. If true, this would equate to a whopping 163 to 245 million people worldwide (by comparison, the U.S. population is 345 million). This is peculiar, because back in听, a review article called the developmental kind of face blindness 鈥渁 very rare condition.鈥� To be fair, the creation of an Internet mailing list and of websites focusing on this condition around the same time dramatically increased awareness for face blindness, but 2 to 3%? This figure, it turns out, is based on听听of 689 German high school and university students. Seventeen of them were found to have face blindness based on a questionnaire, hence 2.5% of the sample. Suffice to say, generalizing from this one study is not a good idea.
We do not truly know how common face blindness actually is in the population at large, and I would be surprised if the number were this high. Then again, it could be high if face blindness is not a disorder after all. What if it鈥檚 just normal variation?
In a provocative paper published in听, Jason Barton and Sherryse Corrow of the University of British Columbia argue that we don鈥檛 know for a fact that prosopagnosia is a separate entity. It could simply be the tail end of a normal distribution. Think of car drivers. Most people are average drivers; some truly excel; and some are really dangerous. What if people with face blindness are simply at the low end of the face recognition spectrum?
Indeed,听听arrived at that 2-3% figure for face blindness, but it did so by deciding (arbitrarily, we could argue) to assign the diagnosis to people who did so poorly on tests of faces that they scored two standard deviations below average. By setting the threshold instead to one standard deviation, or three, we could decide that face blindness is more or less common than 2-3%. It turns this phenomenon into a wet fish: it鈥檚 hard to grab hold of it.
Because at the other end of the spectrum, we have the super-recognizers, people who can identify almost every face they have ever seen. Given the claim that people with developmental face blindness don鈥檛 appear to have anything wrong with their brain, they may simply be part of a normal distribution.
Except that we know this is no longer true. Early studies failed to show any brain differences in people with face blindness, because they were done in five or fewer people at a time, with most of them being听single-case studies. Scientists have now studied enough people with face blindness to see听, like reduced density or volume of grey matter in their temporal lobes (meaning the brain region on each side of your head, near the ears) and disrupted white matter in specific areas known as the ventral occipito-temporal cortices. How these differences come about and how they explain face blindness remain to be solved.
There鈥檚 also the interesting fact that face blindness often runs in families. Oliver Sacks described his older brother, Marcus, has having the same difficulty with faces that he has, unlike their two other brothers, and he suspects their mother may have had a milder form of it, too. While no variation in a single gene has been found that explains developmental prosopagnosia, a hereditary component is strongly suspected in many cases.
And face blindness is not the only condition in which people experience difficulties identifying something banal. There鈥檚 also听, which is not the inability to distinguish telephones from other personal items, but rather difficulty identifying voices, even those of our relatives, in the absence of hearing loss. Just like with face blindness, we also see people at the other end of the spectrum, like Ms. Hariot Daley, the first telephone switchboard operator for the U.S. Congress, who was alleged to be able to recognize by voice all 96 senators and 394 representatives, as well as 300 journalists. No small feat!
Face blindness may appear harmless, but there are consequences to one鈥檚 social life. It brings with it embarrassment and guilt and the desire to limit one鈥檚 social circle. In children, it increases the risk of being harmed by strangers who are mistaken for parents and neighbours.
Attempts have been made at rehabilitating face recognition in people with prosopagnosia, by training them to pay close attention to the spacing between facial features, for example, and the results are听. An听听from a decade ago showed improvement by having participants inhale oxytocin, the social bonding hormone. A study had shown genetic variations in a gene coding for the oxytocin receptor in people with face blindness, hence the idea to give them more of the hormone. Is this the way forward? It鈥檚 hard to know.
There is so much that is still disputed about face blindness. What causes it when it is present early in life? How common is it? Is it even a distinct disorder? Do you really have face blindness if you also have trouble identifying objects? A听听published earlier this year stated that 鈥渢he neuropsychology of face recognition has remained in the Stone Age.鈥�
In the meantime, if you鈥檝e realized that you too have difficulty recognizing people you know just by looking at them, do know that you are not alone.
Take-home message:
- The scientific name for face blindness is 鈥減rosopagnosia,鈥� and some people acquire it due to a tumour or head injury, while others are seemingly born with it
- In people who have had face blindness their whole life, recent brain studies have revealed changes in the brain that may one day explain how face blindness comes about
- There is still much we don鈥檛 know about the condition, such as how common it is or how it may be inherited, and some have argued it may not even be a disorder but simply the tail end of a normal distribution in face identification abilities
