Saturday, 19 January 2013

The Visual Word Form Area


Codex Suprasliensis (source). Texts were less reader-friendly in the past. An ability to read and write meant not only a good livelihood but also reproductive success.

 
The Visual Word Form Area (VWFA) is a brain region that specializes in recognizing written words and letters. Though not essential to reading and writing, it makes these tasks much easier. It plays no role in other mental tasks, as shown when a case of epilepsy was treated by a surgical lesion to the VWFA:

[…] our patient presented a clear-cut reading impairment following surgery, while his performance remained flawless in object recognition and naming, face processing, and general language abilities. (Gaillard et al, 2006).

Some improvement was observed six months afterwards, but reading still took twice as long as it had before surgery.

The VWFA seems to function differently in different human populations, particularly between users of alphabetical script, where symbols represent sounds, and users of logographic script, where symbols represent ideas. Chinese subjects, for instance, process their idea-based symbols with assistance from other brain regions, whereas Westerners process their sound-based symbols only in the VWFA (Liu et al., 2008). Similarly, dyslexics activate this brain region in ways that differ by linguistic background, apparently because of differences in spelling and writing (Paulesu et al., 2001).

Evolutionarily speaking, these population differences seem paradoxical, as does the very existence of the VWFA. As Dehaene and Cohen (2011) note, natural selection could not have created a specialized mental organ for reading because “the invention of writing is too recent and, until the last century, concerned too small a fraction of humanity to have influenced the human genome.” Writing emerged in the Middle East only six thousand years ago, and some societies adopted writing only within the past century. Even in societies that have long been literate, reading and writing were confined to a minority until recent times.

To resolve this paradox, Dehaene and Cohen (2011) argue that our brains deal with word recognition by recycling neurons that were originally meant for face recognition:

Thus, learning to read must involve a ‘neuronal recycling’ process whereby pre-existing cortical systems are harnessed for the novel task of recognizing written words. […] reading acquisition should ‘encroach’ on particular areas of the cortex – those that possess the appropriate receptive fields to recognize the small contrasted shapes that are used as characters, and the appropriate connections to send this information to temporal lobe language areas. […] We have proposed that writing evolved as a recycling of the ventral visual cortex’s competence for extracting configurations of object contours (Dehaene & Cohen, 2011)

For Dehaene and Cohen, the VWFA is not hardwired in our genes. It always takes up the same area of the brain because that is where we can most easily recruit neurons when learning to recognize words. But why then does this recruitment happen so fast in young children and illiterate adults? A study on kindergarten children found that their VWFAs preferentially responded to pictures of letter strings after the subjects had played a grapheme/phoneme correspondence game for a total of 3.6 hours over an 8-week period. This finding is all the more strange because only a few of the children could actually read, and even then only at a rudimentary level (Brem et al., 2010; Dehaene et al., 2010).

So are we born with a ready-to-activate VWFA? And has this mental organ evolved out of an assortment of face-recognition neurons through generations of natural selection? But we’re now back to our evolutionary paradox. How could the VWFA have arisen in no more than six thousand years? The time constraint seems all the more paradoxical if we remember that literacy was confined until recent times to a privileged minority.

But maybe the paradox is only apparent. First, we estimate the literacy rate of past societies from signed documents of one sort or another: wills, court depositions, marriage certificates, etc. (Barr & Kamil, 1996, p. 52). If the “signature” is an ‘X’, the person is deemed to have been illiterate. We can thus measure the admittedly small proportion of people who could read and write cursive script. But a larger proportion could read and write texts of block letters, and even more could read short texts of block letters, e.g., storefront signs and graffiti, while not being able to write. Current historical methods thus underestimate the total proportion of people who had some reading ability.

Second, as Clark (2007) has shown, a selection pressure can affect an entire population even though it acts only on a minority of better-off individuals. As late as the 19th century, the English lower class did not replace itself demographically and was continually replenished by downwardly mobile individuals from the middle and upper classes. The average English man or woman, however poor, was largely descended from yesteryear’s kings, merchants, and scribes.

Finally, new mental organs can arise through natural selection over a fairly short time, especially if they evolve out of pre-existing structures. As Henry Harpending and Gregory Cochran point out:

Even if 40 or 50 thousand years were too short a time for the evolutionary development of a truly new and highly complex mental adaptation, which is by no means certain, it is certainly long enough for some groups to lose such an adaptation, for some groups to develop a highly exaggerated version of an adaptation, or for changes in the triggers or timing of that adaptation to evolve. That is what we see in domesticated dogs, for example, who have entirely lost certain key behavioral adaptations of wolves such as paternal investment. Other wolf behaviors have been exaggerated or distorted (Harpending & Cochran, 2002)

So who needs a VWFA?

Still, is the VWFA really vital to survival? Is it something that natural selection could have favored? As our epileptic patient showed, one can read without a functioning VWFA—admittedly at only half the normal speed.

Keep in mind that texts were a lot less reader-friendly in the past. Because parchment was expensive, writing usually took the form of a continuous stream of characters with little or no punctuation. It was a rare person who could read and write such texts on a sustained basis, so it is no surprise that scribes enjoyed not only good livelihoods but also reproductive success. According to the Book of Sirach [39: 11], “If [a scribe] lives long, he will leave a name greater than a thousand” (Frost, 2011).

When people began to read and write some six thousand years ago, they made use of neurons and neural networks that had served other purposes. It was a make-do solution that nonetheless paved the way for later improvements. If you had a knack for reading and writing, you now had an edge over those who did not, and that knack would be better represented in the next generation. Such mental characteristics would have become more and more widespread with the growing need for people who could process large volumes of textual information on a daily basis.

In this, as in many other ways, humans have directed their own evolution. After creating a new behavior by pushing their envelope of phenotypic plasticity, they gradually acquire a genetic basis for the new phenotype through natural selection for genetic characteristics that make it work better. Humans shape their cultural environment, and this cultural environment in turn shapes humans.

Indeed, there is a suspicious resemblance between the spread of alphabetical writing and the spread of the most recent variant of ASPM, a gene implicated in the regulation of primate brain growth. In humans, a new variant arose some six thousand years ago, apparently somewhere in the Middle East. It then spread outward, becoming more prevalent in the Middle East (37-52% incidence) and Europe (38-50%) than in East Asia (0-25%) (Frost, 2011; Mekel-Bobrov et al., 2005).

References

Barr, R. & M.L. Kamil. (1996). Handbook of Reading Research vol. 2, Routledge.

Brem, S., S. Bach, K. Kucian, T.K. Guttorm, E. Martin, H. Lyytinen, D. Brandeis, & U. Richardson. (2010). Brain sensitivity to print emerges when children learn letter-speech sound correspondences, Proceedings of the National Academy of Sciences U.S.A., 107, 7939–7944.

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World, Princeton University Press, Princeton and Oxford.

Dehaene, S. & L. Cohen. (2011). The unique role of the visual word form area in reading, Trends in Cognitive Sciences, 15, 254-262.

Dehaene, S. et al. (2010) How learning to read changes the cortical networks for vision and language, Science, 330, 1359–1364.

Frost, P. (2011). Human nature or human natures? Futures, 43, 740-748.
http://dx.doi.org/10.1016/j.futures.2011.05.017

Gaillard, R., Naccache, L., P. Pinel, S. Clémenceau, E. Volle, D. Hasboun, S. Dupont, M. Baulac, S. Dehaene, C. Adam, & L. Cohen. (2006). Direct intracranial, fMRI, and lesion evidence for the causal role of left inferotemporal cortex in reading. Neuron, 50, 191-204.

Harpending, H., & G. Cochran. (2002). In our genes, Proceedings of the National Academy of Sciences U.S.A., 99(1), 10-12.

Liu, C., W-T. Zhang, Y-Y Tang, X-Q. Mai, H-C. Chen, T. Tardif, & Y-J. Luo. (2008). The visual word form area: evidence from an fMRI study of implicit processing of Chinese characters. NeuroImage, 40, 1350-1361.

Mekel-Bobrov, N., S.L. Gilbert, P.D. Evans, E.J. Vallender, J.R. Anderson, R.R. Hudson, S.A. Tishkoff, & B.T. Lahn. (2005). Ongoing adaptive evolution of ASPM, a brain size determinant in Homo sapiens, Science, 309, 1720-1722.

Paulesu E., J.F. Démonet, F. Fazio, E. McCrory, V. Chanoine, N. Brunswick et al (2001). Dyslexia: cultural diversity and biological unity, Science, 291, 2165–2167.

25 comments:

Beyond Anon said...


To resolve this paradox, Dehaene and Cohen (2011) argue that our brains deal with word recognition by recycling neurons that were originally meant for face recognition:


This could be tested for by comparing the facial recognition skills of peoples who lack long association with reading and writing (perhaps Papuans) and those in the West or China.

Anonymous said...

This could be tested for by comparing the facial recognition skills of peoples who lack long association with reading and writing (perhaps Papuans) and those in the West or China.

Prosopagnosiacs, I expect would also be an interesting group to study.

Anonymous said...

Has there been any studies of the reading abilities of African Americans and SubSaharan Africans?

Anonymous said...

Knowledge of the VWFA will soon become a hate fact.

Anonymous said...

It seems that the paper on Dyslexia: Cultural Diversity Biological Unity can be found on the web.

Anonymous said...

Hmmm, you didn't mention The Myth of the Visual Word Form Area

Anonymous said...

PDF of The Myth of the Visual Word Form Area

Anonymous said...

PDF for Direct intercranial, fMDI and lesion analysis ...

Anonymous said...

This is a very interesting concept.

It raises the possibility that different racial groups might have a less effective or a more effective VWFA.

To what extent, and I imagine that it is large, does having a less effective VWFA reduce someone's ability to perform in a modern reading intensive environment?

Anonymous said...

More on the VWFA

Sean said...

What modern occupation would the ASPM gene or the Visual Word Form Area have been useful for? Andrew Carnegie And Thomas Edison both started as telegraph operators. Aged 17 Carnegie became one of the first to learn to translate messages 'by ear'.

Today, maybe genetic adaptations for working as a scribe help those working as computer programmers. I wonder if China and the overseas Chinese will be held back in information technology by genetic adaptations to logographic script. Apparently, in China it's essential to have clunky old Windows XP and IE 6; as that's what all the government institutions use.

Peter Fros_ said...

Anon,

I've seen only one study on the VWFA in African Americans:

"By selecting children of equivalent phonological skill, yet diverse socioeconomic backgrounds, we use functional magnetic resonance imaging (fMRI) to demonstrate that a child's experience, as operationalized by SES, can systematically modulate the relationship between phonological language skills and reading-related brain activity in left fusiform and perisylvian regions. Specifically, at lower socioeconomic levels, individual differences in skill result in large differences in brain activation. In contrast, as SES increases, this relationship between phonological language skill and activation is attenuated. Socioeconomic background factors are thus found to modulate brain–behavior relationships in reading, indicating that cognitive, social, and neurobiological influences on reading development are fundamentally intertwined."

Noble, K.G., M.E. Wolmetz1, L.G. Ochs,M.J. Farah, & B.D. McCandliss. (2006). Brain–behavior relationships in reading acquisition are modulated by socioeconomic factors, Developmental Science, 9,642–654.

http://onlinelibrary.wiley.com/doi/10.1111/j.1467-7687.2006.00542.x/abstract;jsessionid=385131120C797F124744A913ADAF982A.d03t02?deniedAccessCustomisedMessage=&userIsAuthenticated=false

In short, African Americans display less activation of the VWFA, even when speaking ability is equivalent to that of control subjects. The authors attribute this deficit to the social and economic environment.

Anon,

"The Myth of the Visual Word Form Area" was written over ten years ago when the evidence for the VWFA was much weaker than it is today. Dehaene and Cohen provide a good review of the literature on this subject.

Anon,

A less effective VWFA makes reading slower, perhaps because it's harder to store character strings in memory. I've worked with people with reading difficulties, and their most common complaint is that reading tires them. They can manage short texts fairly well, but long texts are burdensome.

Sean,

I've done computer programming, and the main problem is conceptualizing the algorithm. Writing the text is a secondary problem (which can be delegated to others). Writing a blog is probably a greater challenge for the VWFA.

Anonymous said...

It seems unlikely that the VWFA is recruiting from face recognition neurons because in more complex societies, people are going to meet more people and thus have to recognize more faces.

However, it seems to me that there might be recruitment from neural networks that were initially designed to recognize camouflaged predators or prey tracks etc.

It would be interesting to test if those who perform poorly on word recognition tasks (as shown by VWFA activation on fMRI) perform better on tasks associated with recognition of predators in their natural habitat, etc.

Anonymous said...

I've done computer programming, and the main problem is conceptualizing the algorithm. Writing the text is a secondary problem (which can be delegated to others). Writing a blog is probably a greater challenge for the VWFA.

Isn't reading code an important part of learning programming?

Anonymous said...

The Unique role of the VWFA in reading

Beyond Anon said...


Isn't reading code an important part of learning programming?


Precisely. You have to be able to read code to learn how to program at the very least. However, all modern programming positions require the holders to read lots of code to:

1. Improve the code to perform new functions or be more efficient,

2. Fix bugs.

Indeed, very few roles in modern societies do not require lots of reading. Only back-breaking work, stoop labor, and sports do not require lots of reading, and even there you will find people who can read who can also do that work.

If reading is a problem for your lineage in the modern world, your lineage is on the way out.

Sean said...

Black Africans needed facial recognition skills as much as anyone. I believe they are at least as fast as Europeans at learning to put new faces to names. Dehaene and Cohen's theory would lead one to expect Africans' face recognition and naming skills would, through recycling, enable them to read with no problem at all. Whatever their SES.

Mate acquisition would require certain phonological language skills. Namely, the ability to 'represent' oneself; superficial and difficult to measure perhaps, but nonetheless real. In a polygynous mating system vapid 'smooth talking' would be selected for, I think.

The interesting thing to me is if something was lost in gaining VWFA and related adaptations; could 'face to face' social intelligence be attenuated?

Anonymous said...

Black Africans needed facial recognition skills as much as anyone.

This is crap. Brain tissue is expensive to develop and to maintain. It is also expensive during birth.

The amount of brain tissue required for face recognition is proportional to population density, and East Asians, Middle Easterners and Europeans have lived in much more dense societies than black Africans.

Anonymous said...

It would be interesting to get fMRI measurements of various racial groups.

I suspect that the key genetic selection mechanism here will be for neural plasticity, especially the ability to recruit existing neural tissue for novel uses.

Some people will have genes that will enable neural plasticity and others wont. Not having that plasticity will mean that such individuals and lineages will be driven to extinction.

Sean said...

Maybe Dunbar's Number (which takes up brainpower as it increases) is less for Africans, but theory of mind skills based on the ability to accurately 'read' others from their facial expressions, is more essential in a volatile society where it is easy to get edged out by those with better social skills. I think Africans would need those specialized face reading neurons more than other peoples.

If neural plasticity enables adjustments for reproductive success, and whites have more plasticity (as implied), how explain the current white birthrate? Surely plasticity would enable those who have it to adapt better to any circumstances that require specialized mental functions. No, whites went beyond plasticity; they are hardwired now, and the side effect of their previous adaptations are now deleterious to survival.

A beta wolf spends his time cowering, but has plasticity in the sense that, if the alpha position becomes vacant he will be fired up and behave like an alpha; or 'big man'. Humans have odd personalities that are fixed. For instance. in Pride and Prejudice the character of Darcy is painfully awkward at balls. He detests dancing is prone to lengthy silences, and the first time he proposes to Elizabeth Bennett he delivers a strange monologue. (Darcy eventually gets the girl; he is wealthy though.) Is that kind of odd personality more common in European or African men? Selection for winning women’s hearts wasn't left untouched by selection for being a clerk. I think there were deleterious side effects from selection for special mental functions of a non social type, and pacification.

Anonymous said...


Maybe Dunbar's Number (which takes up brainpower as it increases) is less for Africans, but theory of mind skills based on the ability to accurately 'read' others from their facial expressions, is more essential in a volatile society where it is easy to get edged out by those with better social skills.


Ahhh, so now you have walked it back a bit and also demonstrate that you don't understand the claims.

1. Facial expressions are limited compared with the number of individuals that one might come in contact with, and reading facial expressions is likely hard-wired in all humans. In addition, truly gifted social manipulators can fake their facial expressions.

2. One needs to be able to recognize faces so one can remember past interactions with those individuals and thus predict future outcomes and strategies.

The number of social interactions one will engage in is greater in the more complex societies outside southern Africa. This has been so for far longer in those groups outside southern Africa, possibly as much as 100 generations longer. Selection thus has had longer to operate.

As to the following:

If neural plasticity enables adjustments for reproductive success, and whites have more plasticity (as implied), how explain the current white birthrate? Surely plasticity would enable those who have it to adapt better to any circumstances that require specialized mental functions. No, whites went beyond plasticity; they are hardwired now, and the side effect of their previous adaptations are now deleterious to survival


You clearly do not understand selection. I would also note that certain groups of religious whites actually have quite high birth rates.

Also, I don't think I implied whites. I was thinking of East Asians as well.

Sean said...

"The intriguing possibility that our face-perception abilities suffer in proportion to our reading skills will be explored in future research," Here.

If a scribe had a rare and highly marketable skill; the status/resources to make him a 'catch' would follow, hence it wouldn't have mattered very much if he was socially awkward. In Africa there was no need to divert neuronal processing to help with reading. However, African men ran a far higher risk of being excluded from reproduction if they lacked social skills, because of polygyny. The stakes of purely social interaction were higher for African men, and in consequence face-perception abilities would have been selected for.

Through Confucian exam culture, East Asians have been intensively selected for reading ability. In my opinion East Asian men are relatively nerdy.

Anonymous said...

It would be interesting to test Aboriginal Australians and mixed Caucasian and Aboriginal Australians or mixed Chinese and Aboriginal Australians to see:

1. To what extent the VWFA is activated among AAs when presented with written material vs, say pictures of tracks of animals they hunted [1]

2. To what extent those of mixed ancestry improve their reading abilities compared with those of less admixture.

[1] It seems obvious that tracking abilities requires some training, but that there would have to be some in-built support.

Sean said...

struccw1209There are brain genes that have been selected for in Black Africans. They are not hunter gatherers.

Overlord of the Über-Feral said...

Very interesting post. Language is the big one, in terms of issues around engagement with human genetics. Without language, no writing; without writing, no nowt (in terms of issues around advanced civilization).

BTW, this will give your VWFA a work-out:

http://www.omniglot.com/writing/rotor.htm