Luke the Evangelist (source: British Library). In the past, only a minority could read long texts of cursive writing. But many more could read short texts of block writing.
The Visual Word Form Area (VWFA) is a specialized part of the brain that helps us recognize written words and letters. If it is subjected to a surgical lesion, the patient will suffer a clear impairment to reading ability but not to recognition of objects, names, or faces or to general language abilities. There will be some improvement over the next six months, but reading will still take twice as long as it had before surgery (Gaillard et al, 2006).
Most of the initial skepticism over the existence of the VWFA has disappeared. There does seem to be, however, much variability in its size. An area that may fall within this mental organ in one person may fall outside it in someone else (Glezer and Riesenhuber, 2013).
In addition to word recognition, the VWFA may participate in higher-level processing of word meaning:
[It seems that] the VWFA would not only be recruited at an early stage for allowing low-level (script processing) word processing as has been previously instantiated (Pammer et al., 2004; Dehaene and Cohen, 2011), but also at a later stage for gating high-level (lexico-semantic) processing. Such late semantic gateway would not be selective to the VWFA but rather emerge in the posterior LOT and extend anteriorly to the VWFA. (Levy et al., 2013)
The VWFA is described in the above study as a “bottleneck to consciousness.” It helps us not only to recognize words on a page but also to understand what the words mean. To me, this makes sense. I’m better at thinking through an idea and its implications if I can write it down and then read it. There thus seems to be a single mental pathway that does double duty: processing character strings (words) and processing higher-level concepts.
The VWFA functions differently in different human populations. The difference is striking between people who use alphabetical script, where each symbol represents a sound, and those who use logographic script, where each symbol represents an idea. Chinese subjects 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).
Hardwired or softwired?
For Dehaene and Cohen (2011), the VWFA is not a hardwired mental organ. They argue that it occupies 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? When kindergarten children were asked to play a grapheme/phoneme correspondence game, their VWFAs preferentially responded to pictures of letter strings after a total of 3.6 hours over an 8-week period. It is worth noting that only a few of these children could actually read, and even then only at a rudimentary level (Brem et al., 2010; Dehaene et al., 2010).
But the alternative view, hardwiring, is also hard to accept. Reading began not in the Paleolithic but in historic times, less than 6,000 years ago. Widespread literacy is even more recent, and there are still many societies where most people cannot read or write. How could an entirely new mental organ have evolved over so short a time?
Yet this alternative view may not be so farfetched. Let’s examine the two main objections.
Was there not enough time for natural selection to work?
The VWFA did not evolve out of nothing. It seems to be a population of neurons that originally served to recognize faces (Dehaene and Cohen, 2011). This sort of recycling is a common pathway for natural selection and explains much of the apparent rapidity of evolution. A complex mental adaptation may take a long time to evolve, but much less time is needed to develop an exaggerated version of it or to alter when and how it becomes activated (Harpending and Cochran, 2002).
Indeed, parallel to the way alphabetical reading ability has spread historically and geographically, there is a similar spread of the latest variant of ASPM, a gene implicated in the regulation of brain growth. In humans, a new variant arose about 6,000 years ago in the Middle East. It eventually became 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).
Would it have benefited too few people to have been favored by natural selection?
There is some debate over the relative recentness of literacy. It is true that before the modern era only a small minority could read long texts of cursive writing. But the ability to read short texts of block writing was much more widespread, as evidenced by the prevalence of graffiti and storefront signs. We should also keep in mind that the literate few contributed disproportionately to the gene pool of subsequent generations. Clark (2007) has shown that the English lower class is largely descended from people who were middle or upper class a few centuries ago. In the ancient world, there was a perception that scribes enjoyed reproductive success. The Book of Sirach [39: 11] states: “If [a scribe] lives long, he will leave a name greater than a thousand.”
There may have been positive feedback between reading ability and the cultural opportunities it created. One example is the scientific revolution in Western Europe (15th - 18th centuries), which took off once a critical mass of scholars could read each other’s papers. In short, reading and writing are advantageous to the extent that other people can read and write. While this kind of feedback loop is self-evident, its biological implications may be less so. The same feedback loop would have steadily ratcheted up selection for the VWFA and, subsequently, for higher-level faculties. This might explain why the VWFA evolved beyond word recognition per se and towards lexico-semantic tasks.
One priority would be to study the VWFA in populations that have become literate only in recent times. What form, if any, does it take in such people? A study in New York elementary schools found that VWFA activation varied with socioeconomic status. In students from high SES families, activation seemed to be more hardwired and less dependent on familiarity with the way sounds are visually represented. Unfortunately, there was no attempt to break the data down by ethnic background (Noble et al., 2006).
At present, high VWFA activation is attributed to an environment where reading material is accessible and parents very supportive, this being in turn attributed to high SES. Yet reading material is ubiquitous nowadays. And how crucial is parental support? As a child, I read almost always on my own with little encouragement at home or school. My teachers were in fact annoyed by my habit of sneaking into the small storage room where old textbooks and encyclopedias were kept (we had no library). “If you’ve finished your assignment, stay at your desk. Is that clear?!”
Nonetheless, I read voraciously, even when I couldn’t understand half of what I read. Strange new words were a source of pleasure, and I would often read and reread the same texts simply because I liked the flow of the words and the images they conjured up.
Brem, S., S. Bach, K. Kucian, T.K. Guttorm, E. Martin, H. Lyytinen, D. Brandeis, and 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.http://psyserv06.psy.sbg.ac.at:5916/fetch/PDF/20395549.pdf
Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World, Princeton University Press, Princeton and Oxford.
Dehaene, S. and L. Cohen. (2011). The unique role of the visual word form area in reading, Trends in Cognitive Sciences, 15, 254-262.http://www.cnbc.pitt.edu/~plaut/VisCog/papers/DehaeneCohen11TICS.VWFA.pdf
Dehaene, S. et al. (2010). How learning to read changes the cortical networks for vision and language, Science, 330, 1359–1364.http://gondabrain.ls.biu.ac.il/Neuroling/courses/877/Dehaene_Science2010.pdf
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, and L. Cohen. (2006). Direct intracranial, fMRI, and lesion evidence for the causal role of left inferotemporal cortex in reading, Neuron, 50, 191-204.http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.76.7620&rep=rep1&type=pdf
Glezer, L.S. and M. Riesenhuber. (2013). Individual variability in location impacts orthographic selectivity in the “Visual Word Form Area”, The Journal of Neuroscience, 33(27), 11221–11226.http://www.jneurosci.org/content/33/27/11221.full
Harpending, H., and G. Cochran. (2002). In our genes, Proceedings of the National Academy of Sciences USA, 99(1), 10-12.http://www.wcas.northwestern.edu/nescan/2008-2009%20papers/harpending%20-%20in%20our%20genes.pdf
Levy, J., J.R Vidal, R. Oostenveld, I. FitzPatrick, J-F. Démonet, and P. Fries. (2013). Alpha-band suppression in the Visual Word Form Area as a functional bottleneck to consciousness, NeuroImage,78C, 33-45.http://hal.inria.fr/docs/00/81/96/67/PDF/Levy_et_al.pdf
Liu, C., W-T. Zhang, Y-Y Tang, X-Q. Mai, H-C. Chen, T. Tardif, and Y-J. Luo. (2008). The visual word form area: evidence from an fMRI study of implicit processing of Chinese characters, NeuroImage, 40, 1350-1361.http://psychbrain.bnu.edu.cn/teachcms/res_base/teachcms/upload/channel/file/2010_4/11_25/6hlcggx7rk3z.pdf
Mekel-Bobrov, N., S.L. Gilbert, P.D. Evans, E.J. Vallender, J.R. Anderson, R.R. Hudson, S.A. Tishkoff, and B.T. Lahn. (2005). Ongoing adaptive evolution of ASPM, a brain size determinant in Homo sapiens, Science, 309, 1720-1722.
Noble, K.G., M.E. Wolmetz, L.G. Ochs, M.J. Farah, and B.D. McCandliss. (2006). Brain–behavior relationships in reading acquisition are modulated by socioeconomic factors, Developmental Science, 9, 642–654.http://www.cumc.columbia.edu/dept/sergievsky/fs/publications/Noble-et-al-2006-2.pdf
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.http://www.drru-research.org/data/resources/42/Paulesu-et-al-2001.pdf