Summary: Prosopagnosia, or face blindness, is thought to affect up to 2.5% of the population. However, researchers say prosopagnosia can be on a spectrum and the number of cases can be much higher, estimating that up to 1 in 33 people may meet the criteria for face blindness.
Source: Harvard
It has once been estimated that face blindness, a mystifying condition that can make us think we recognize people we have never met or make us not recognize those we have, affects between 2 and 2.5% of people in the world.
Now, a new study by researchers from Harvard Medical School (HMS) and the VA Boston Healthcare System provides new insights into the disorder, suggesting it may be more common than currently thought.
Published in February 2023 in Cortex, study results indicate that as many as one in 33 people (3.08%) may meet the criteria for face blindness or prosopagnosia. That translates to more than 10 million Americans, the research team said.
The study found similar face-matching performance between people diagnosed with prosopagnosia using stricter versus looser criteria, suggesting that diagnostic criteria should be broadened to be more inclusive. This could lead to new diagnoses among millions of people who may have the disorder but don’t realize it.
In the new study, led by Joseph DeGutis, associate professor of psychiatry at HMS in VA Boston, researchers found that face blindness falls on a spectrum – which can vary in severity and presentation – rather than representing a discrete group . The authors also provide diagnostic suggestions for identifying mild and major forms of prosopagnosia based on the guidelines for major and mild neurocognitive disorders in the DSM5the 5th edition of Diagnostic and Statistical Manual of Mental Disorders.
The study results are based on an online questionnaire and tests administered to 3,341 people. First, the researchers asked the participants if they had difficulty recognizing faces in their everyday life. Then they administered two objective tests to determine whether they had difficulty learning new faces or recognizing very familiar and famous faces.
The results showed that 31 of 3,341 individuals had major prosopagnosia, while 72 of 3,341 had a milder form. The researchers also observed that there were no distinct, well-divided groups of people with low or high ability to recognize faces. Rather, the ability to recognize faces seemed to be on a continuum, they said.
Finally, the researchers compared face-matching scores in people with prosopagnosia diagnosed using different criteria and found that using more stringent diagnostic thresholds did not correlate with face-matching scores. weaker faces.
Harvard Medicine News spoke with DeGutis, the study’s lead author, about the implications of the findings.
Harvard Medicine News: Let’s start with the basics. What are the causes of face blindness?
FromGutis: Prosopagnosia, or face blindness, can be caused by brain damage to the occipital or temporal regions, called acquired prosopagnosia, which affects one in 30,000 people in the United States. Prosopagnosia can also be a lifelong condition caused by genetic or developmental abnormalities, called developmental prosopagnosia, affecting one in 33 people.
HMNews: It’s a fascinating condition, but some might say it’s not a serious health condition, so why is it important to study and understand it?
FromGutis: First, face blindness can be a socially debilitating disorder that can limit employment opportunities. For example, networking is extremely difficult for people with prosopagnosia and can cause social distress and embarrassment. Recognizing someone is a social signal, indicating that “you are important to me”.
Prosopagnosia can also affect people on the autism spectrum and can also be a consequence of age-related cognitive decline. In a world where social isolation is on the rise, especially among adolescents and young adults, fostering and maintaining social connections and good face-to-face interactions are more important than ever.
HMNews: What sparked your interest in this area? What intrigues you most about how the brain sees and remembers faces and why?
FromGutis: Face blindness is fascinating on many levels. Humans are remarkably good at recognizing familiar faces and it’s done with very little effort. We know that this “superpower” of the face relies on several specific perceptual processes: holistic processing of the face – seeing the face as an integrated whole, for example; memory process, easily associating faces with person-related knowledge; as well as mechanisms and specialized brain regions, such as the fusiform facial area.
Our knowledge of facial recognition in healthy individuals provides a very solid framework for understanding how these processes can break down into prosopagnosia. The processes also provide clues on how to improve facial recognition in people with face blindness, which is one of our lab’s main goals. Finally, the study of prosopagnosia is fascinating from a phenomenological point of view: what do people with face blindness actually “see” when they look at a face? What comes to mind when they think of the face of a familiar friend?
HMNews: You say your findings call for a broadening of diagnostic criteria. Why is this important?
FromGutis: This is important on several levels. First, the majority of researchers have used diagnostic criteria that are too strict, and many people with significant problems with facial recognition in daily life have been mistakenly told that they do not have prosopagnosia. Broadening the diagnosis is important because knowing that you have real objective evidence of prosopagnosia, even a mild form, can help you take steps to reduce its negative impacts on daily life, such as telling co-workers or seeking treatment. .
Recent evidence suggests that people with milder forms of face blindness may benefit more from certain treatments than people with more severe forms of the disease. These treatments may include cognitive training to improve perceptual abilities or training aimed directly at improving facial associations.
Finally, factors such as age-related cognitive decline and social anxiety can further worsen facial recognition abilities. Knowing if you have mild prosopagnosia could help you keep tabs on other situational or age-related declines in facial recognition ability.
HMNews: What do you want clinicians and sufferers to take away from these results?
FromGutis: The take-home message is that prosopagnosia sits on a continuum and that stricter or looser diagnostic criteria used in studies of prosopagnosia over the past 13 years have identified mechanistically very similar populations, justifying the expansion. criteria to include those with milder forms.
Another take-home message is the importance of using a combination of self-reported daily living difficulties and validated objective measures when diagnosing prosopagnosia. There are pros and cons to relying solely on self-reports, as it can be difficult to judge one’s own abilities or to rely solely on objective laboratory measurements that may not reflect daily life.
Authorship, Funding, Disclosures
Other authors included Kanisha Bahierathan, Katherine Barahona, EunMyoung Lee, Travis Evans, Hye Min Shin, and Jirapat Likitlersuang of Harvard Medical School and VA Boston Healthcare System; Maruti Mishra from the University of Richmond; and Jeremy Wilmer of Wellesley College.
See also
Funding: This study was supported by a National Eye Institute grant awarded to Joseph DeGutis (R01EY026057).
The authors have no disclosures to report.
About this visual neuroscience and face blindness research news
Author: Ekaterina Pesheva
Source: Harvard
Contact: Ekaterina Pesheva – Harvard
Picture: Image is in public domain
Original research: Free access.
“How common is developmental prosopagnosia? An Empirical Assessment of Different Diagnostic Cutoffs” by Joseph DeGutis et al. Cortex
Abstract
How common is developmental prosopagnosia? An empirical assessment of the different diagnostic thresholds
The prevalence of developmental prosopagnosia (DP), facial recognition deficits across the lifespan, is widely reported to be 2-2.5%. However, PD has been diagnosed in different ways in different studies, resulting in different prevalence rates.
In the current survey, we estimated the prevalence range of PD by administering well-validated objective and subjective facial recognition measures to an unselected web-based sample of 3,116 people aged 18-55 and applying the thresholds diagnosis of PD over the past 13 years.
We found estimated prevalence rates ranging from 0.64 to 5.42% when using a z-score approach and from 0.13 to 2.95% when using a score approach. percentile, the cutoffs most commonly used by researchers with a prevalence rate of 0.93% (z-score, 0.45% when using percentiles).
We then used multiple cluster analyzes to examine whether there was a natural grouping of weaker facial recognizers, but failed to find a consistent grouping beyond those whose facial recognition is generally above average. .
Finally, we investigated whether PD studies with more relaxed diagnostic thresholds were associated with better performance on the Cambridge Face Perception Test.
In a sample of 43 studies, there was a weak, non-significant association between greater diagnostic rigor and reduced Accuracy of face perception DP (Kendall’s tau-b correlation, τb = 0.176 z-score; τb = 0.111 percentiles).
Together, these results suggest that the researchers used more conservative diagnostic thresholds for PD than the widely reported prevalence of 2–2.5%. We discuss the strengths and weaknesses of using more inclusive cutoffs, such as identifying mild and major forms of PD based on DSM-5.