Too much prosopagnosia

(referred here by Dave's blog)

The article makes no claim that this is a genetically acquired trait -- In fact, it claims to be more environmental:

There are two broad categories of prosopagnosia. Most documented cases have been of acquired prosopagnosia, due to brain damage suffered after maturity from head trauma, stroke, and degenerative diseases. The other type is called developmental prosopagnosia. These individuals can have similar symptoms but with no evidence of brain damage. It is this group that may be the most common.

it claims to be more environmental

i'm busy right now, but the key is my understanding is that human face recognition is a pretty established 'cognitive module.' it isn't something that's 'learned.' i suppose there could be environmental variation, but this trait should be 'fixed' in a population because it is very fitness relevant.

Right, but Dana was just saying that prosopagnosia is like a broken leg. You have a stroke that only affects that part of your brain.

BTW -- title is a Devo reference?

ah, ok, will look into this later....

I agree with you Razib, it sound more innate than from learning to me. So 2% on a almost innate cognitive module, it's a lot !

"In other words, 2% is just way too high for something that seems so clearly maladaptive."

So is it possible that homosexuality is an inherited trait? Though some gays reproduce, homosexuality dramatically diminishes an individual's chance of reproducing. It is clearly maladaptive.

Just curious.

So is it possible that homosexuality is an inherited trait? Though some gays reproduce, homosexuality dramatically diminishes an individual's chance of reproducing. It is clearly maladaptive.

Just curious.

hm. :) i think it is biological, but probably not that genetic (latest concordance studies between MZ twins = .25, not .5).

"i think it is biological, but probably not that genetic (latest concordance studies between MZ twins = .25, not .5).

Biological, but probably not that genetic? Hmmmm. Is that the reason why MZ twins sometimes look so different -- random circumstances in utero; or are there a number of other biological but non-genetic culprits?

"might be found in ~2% of the population"
Whoaa! I'm very skeptical. I wouldn't even guess that any of the 3300+ high-school students that I attended with would have such a disability, which prima facie seems totally crippling. This would seemingly cause a profound reduction in fitness for a significant part of the population.

Would there be any stats about it's incidence w.r.t. race or sex, or co-occurance w/ other pathologies?

i think it is biological, but probably not that genetic

Yes, some studies are looking at the effects of hormone exposure in utero on sexual orientation. BUT -- This is exactly the point the article on prospagnosia was making - that there may be some biological influences (other than genetics) from the environment that affects its development. This is similar to synesthesia - some estimates are around 1% of the general population that has a form of synesthesia. It has a genetic component, but it also has environmental influences.

This is exactly the point the article on prospagnosia was making - that there may be some biological influences (other than genetics) from the environment that affects its development.

actually, the article was rather vague. can you point me to a more technical treatment of the issue?

thanks

I wonder, is it any more maladaptive than, say, lefthandedness or colorblindness?

Also, innate doesn't mean genetic. It could be the result of neurological developments in utero, for example, or even of postnatal factors similar to those that shape language development. This is one way that even severely maladapative conditions manage to appear consistently.

I wonder, is it any more maladaptive than, say, lefthandedness or colorblindness?

colorblindness is a sex-linked issue that emerges out of high mutational rates on the opsin genes, from what i recall. also, there is some evidence that colorblind males can detect movement and what not better against a background. remember that most mammals are nearly colorblind, fruit eating primates are an exception, not the rule. as for lefthandness, it might be an issue of frequency dependent selection. in sort, both might decrease (or increase) fitness somewhat, but i doubt it is an big issue.

It could be the result of neurological developments in utero, for example, or even of postnatal factors similar to those that shape language development. This is one way that even severely maladapative conditions manage to appear consistently.

granted, but these stochastic developmental issues are often conditioned on prior genetics. in other words, a certain genetic profile seems to impart greater robusticity and insulate one from random acts of nature to some extent.

"Robusticity," eh? I thought you made that up until I googled it. Why not robustness? Lit Crit envy? Weird.

I googled around for genetic vs trauma-related prosopagnosia -- nothing clear. Seems that most research focused on the trauma-related kind since stroke, trauma, etc. are already on record for that person, and faceblindness occurs shortly afterward & is so noticed better. The claim is that developmental prosopagnosia is underreported since they don't suffer a stroke or whatever -- but that seems like it's BS. Sure, it's embarrassing to admit you can't remember faces, but I'd think that those around you would easily notice & tell you to go see a doctor. But who knows.

Of course, this might be a normally distributed quantitative trait on some level (this seems plausible, to an extent), and this "2%" are popping up on a very sensitive measure, and only a far smaller % are extreme enough to qualify as pathological. An analogy might be between Asperger's Syndrome and Austism.

This makes sense to me. Most of the folks that I know who have prosopagnosia (including myself) aren't completely face-blind. Many have no problems recognizing people that are very familiar to them (spouse, girlfriend, boyfriend, family members) -- someone you see a lot -- but have a harder time recognizing people they sort-of know out of context. And out of context is really the key. One might easily recognize one's doctor in their office -- but not if you happen to see them in the grocery store.

Agnostic -- I never realized I was face-blind until recently -- even though throughout my life I've been "rude" to people that I didn't say hello to because I didn't see them. I just always thought I was too busy thinking about something to notice people around me. :p And, most people have just thought I was a little flakey. But, no one ever told me to go to a doctor. There's a lot of developmental prosopagnosia around that goes underreported. How was I ever to know that other people didn't experience the world like me? I just assumed that other people saw the world (or didn't see it!) the same way I did.

actually, the article was rather vague. can you point me to a more technical treatment of the issue?

ACK! I didn't want to take time for this, but here ya go. the first one is co-authored by Ken Nakayama, cited in the original article...

This brief review makes it clear that there are many possible ways that such a complex and protracted process could be disrupted. An absence of normal input to right hemisphere mechanisms could arise for any number of reasons: lack of social contact, failure to direct attention to faces, or low-level visual problems such as infantile cataracts, severe uncorrected myopia, or amblyopia in which input from the left eye is suppressed. The many cortical recognition mechanisms involved with face recognition could fail to develop due to environmental factors, genetic deficits, or brain damage anytime during development.

Duchaine, B. & Nakayama, K. (2005). Dissociations of face and object recognition in developmental prosopagnosia. Journal of cognitive neuroscience, 17(2), 249-261.

The most common cause of prosopagnosia is a posterior cerebral artery stroke, although any process which can damage the occipitotemporal lobes may be responsible. Thus, other etiologies include a transient ischemic attack, carbon monoxide poisoning, temporal lobectomy, encephalitis, neoplasms, right temporal lobe atrophy, trauma, Parkinson's disease, and Alzheimer's disease. More diffuse processes include alcohol intoxication, Asperger syndrome (a form of autism), and psychosis due to schizophrenia and mescaline.

Golsdmith, Z. T. & Liu, G. T. (2001). Facial recognition and prosopagnosia: past and present concepts. Neuro-opthalmology, 25(4), 177-192.

colorblindness is a sex-linked issue that emerges out of high mutational rates on the opsin genes, from what i recall. also, there is some evidence that colorblind males can detect movement and what not better against a background. remember that most mammals are nearly colorblind, fruit eating primates are an exception, not the rule. as for lefthandness, it might be an issue of frequency dependent selection. in sort, both might decrease (or increase) fitness somewhat, but i doubt it is an big issue.

That was sort of my point. Lefthandedness does seem to increase accident rates somewhat, so it is at least slightly maladaptive. Colorblindness in humans is somewhat different than it is in other animals, simply because human society and the habits we inculcate in our kids are at least partly based on the fact that most humans can see colors.

Also, many if not most colorblind animals rely mainly on other much better senses, such as hearing and smell. Vision is a relatively minor sense to a dog - about as important as smell is to a human. So I'm not sure that animal models are appropriate here.

That said, I don't think that colorblindness is fearsomely maladaptive in humans. And I can't really see why prosopagnosia would be either. Someone who has it almost always develops coping mechanisms. In ancient times the most important threats to survival wouldn't have been affected by this condition in any case, so it wouldn't have been selected against very strongly.

these stochastic developmental issues are often conditioned on prior genetics. in other words, a certain genetic profile seems to impart greater robusticity and insulate one from random acts of nature to some extent.

We don't know that the triggering factors are random. It might be any of a number of factors or combinations of factors, some of which may be more common in modern times than they were when our genome was getting its groove on.

What I'm getting at here is that we really don't have any solid reason to doubt these results. They're surprising, yes, but mainly because I don't think anyone suspected that 2 out of every hundred people they know might not be able to recognize their faces. We don't know enough about what causes this condition to have any firm opinion on results themselves, IMO.

i ran across your interesting discussion of our estimate of the incidence of prosopagnosia, and i wanted to chime in with my thoughts on the 2% figure.

it's worth keeping in mind that in modern environments we see hundreds or thousands of faces a day in a wide variety of contexts. in ancestral environments, we undoubtedly saw far fewer faces than we do today. as a result, face recognition abilities are under much greater strain than they used to be. it could be that many prosopagnosics in current environments would have done just fine in ancestral environments.

i also would be very surprised if individuals in the bottom 2% of the population don't regularly experience face recognition difficulties that have social repercussions. i'm probably somewhat below average at face recognition (my wife often laughs at my inability to recognize celebrities), but i'm definitely not prosopagnosic. nevertheless, i have occasionally gotten in awkward situations, because i failed to recognize a face i should have recognized. if i was the bottom 2%, i expect this would happen far more often.

I am not a genetics whiz, just a stay-at-home-mom that used to be an electrical engineer. I am clearly out of my league here, but I do have the critical reasoning/analytical skills to somewhat follow. What does qualify me somewhat is that I have a just-turned 5 yr old son that is significantly face blind. I always knew he was different than other kids -- he could not recognize friends from across the street or across the playground, even though he seemed incredibly bright, but I didn't know why. Oddly enough, I realized what was going on after watching an episode of the now-cancelled TV show 3 Lbs. -- it was like a light bulb going off! After some questioning, it turns out that he recognizes people only by their voice, hair and clothes. If I get new clothes, he has told me that he barely recognizes me in those new clothes (his words, not mine). He does not recognize pictures of himself or me (on the refrigerator - "how many pictures of me are there on the refrigerator?"). I asked him how he knows it is me when I pick him up from school: "Sometimes I recognize your clothes.". What if you don't recognize my clothes?: "I just wait.". Wait for what?: "For you to say something.".

My son is left handed; his greatest strength is language - he has a working vocabulary that rivals many adults (everyone mentions this, it's not just my assessment); he has a facility for understanding complex mathematical functions for his age, e.g. mulitiplication; he has excellent pattern recognition skills (can build 600+ piece Lego models by following the illustrated directions - considered for ages 8-16); has no interest in reading although he can sound out a word if you spell it out loud for him; had extreme colic as an infant that did not go away until he was 9 months old; has anosmia on the right side of his nose; and has a huge amount of food allergies and sensitivities (egg, soy, gluten, dairy, mold food allergy, fruit allergies). Can any of these things be related? I wonder.

He is incredibly bright, but obviously deficient in this area. Turn out that his dad is too -- I never knew. I have taken the tests at the following website: http://www.icn.ucl.ac.uk/facetests/myabilities.php as well as others, and always score 96% or higher (some 99%). When I told my husband about it, he at first thought I was crazy, but then recalled how when he was in grade school, they merged two schools together and he felt like he could no longer tell who anyone was -- he said it took him a couple of months to figure things out. Somehow, my son's face blindness seems to be much worse than my husbands. Today, I asked my husband to take the tests on this site. He was 86% for Famous Faces, but then tried to take the Old-New Faces and came out and told me he didn't even think he could do it. He's going to try tomorrow morning after being well rested.

I obviously have more than an academic interest in this condition. I enjoyed reading your blog, and know that I am posting well after the original entry. I would appreciate any more of your thoughts on this issue as I am trying to learn as much as I can.

"In other words, 2% is just way too high for something that seems so clearly maladaptive. This is only a few steps short of finding out that 2% of the population was incapable of language, recognizing faces is a necessary precondition for much of human sociality."

I disagree. First of all, humans are remarkably good at finding strategies for hiding their disabilities, and they often enlist the support of confidants in doing so. Second, in many cases a disability is accompanied by a unique ability. Genetics is not just about finding a single optimum configuration, but about exploring all possible alternatives and trade-offs. (Man has clearly not yet reached the pinnacle of perfection, and there are still many different avenues to explore.) Many people see severe social maladaptiveness in nerds, but much of the technology that keeps our society running is based on their designs. Perhaps people with "genetic-based" prosopagnosia have some as-yet-undiscovered abilities that most of us lack.