In November, Stan Dehaene is coming to Maryland to give the annual Baggett Lectures on language and cognition. To “prepare” myself, I have just finished reading his last book, Reading in the Brain, which I can highly recommend. It appears that our friends in cog-neuro have begun to understand the underlying mechanisms behind our ability to read, tracing it to a confluence of capacities lodged, not surprisingly, in the visual system and FL. The reading trick, again not a surprise, is to figure out how to link morphemes to graphemes (I’m talking about alphabetic reading systems here) and this problem turns out to piggy back on some rather deep facts about the mechanisms that the visual system uses to interpret the physical environment and how different alphabets express the relevant morphemes in a language. It seems that letters like ‘T’ and ‘F,’ ‘K,’ ‘Y,’ and ‘L’ are “proto-letters” and they exploit capacities central in parsing a visual scene:
The shape T, for example, is extremely frequent in natural scenes. Whenever one object masks another, their contours always form a T-junction. Thus neurons that act as “T-detectors” could help determine which object is on front of which.
Other characteristic configurations, like the shapes of a Y and an F are found at places where several objects of an object meet…All of these fragments of shapes belong to what is known as “non-accidental properties” of visual scenes because they are unlikely to occur accidentally in the absence of any object…(loc 2138 e-book version).
These “natural” shapes find their way into many alphabetic systems thereby allowing the capacities of the visual system to be recycled to undergird the capacity to read.
The second leg of the reading capacity lies in tying graphemes to morphemes. This turns out to be rather difficult. I was surprised to find out (remember, I come from a philosophy department so I know virtually no phonology and, come to think of it, very little else) that the emerging consensus opinion concerning dyslexia is that stems from “an anomaly in the phonological processing of speech sounds” (loc 3779). It seems that the majority of dyslexic kids have trouble processing phonemes in general (i.e. independent of reading) and that’s why they have trouble matching graphemes (letters) to morphemes in reading. In other words, it seems that dyslexia is largely a speech processing problem (loc 3801). Dehaene calls this is a “revolutionary idea,” one that seems “barely credible,” but he argues that the evidence points to dyslexics having a problem with “phonemic awareness” and hence have trouble with the necessary phoneme-grapheme mapping mastery of which is required for fluent reading (loc 3801).
Interesting to me was the information that dyslexia appears to be far less apparent in some cultures than in others. For example, it seems that “dyslexia is hardly ever diagnosed in Italy” (loc 3876), whereas it is a pretty common syndrome in French and English reading cultures. Could dyslexia be nothing more than a cultural “disease”? Seems unlikely. And indeed, it is not so.
Rather, the biological propensity is rather stable across readers of different languages but the practical reading problem becomes acute only in cases where “writing systems [are] so opaque that they put a major stress on the brain linking vision to language” (loc 3898).
How this was demonstrated was rather neat. A research group in Milan (headed by Eraldo Paulesu) scoured Italy for reading impaired individuals who superficially did not seem particularly impaired. However, careful testing showed they were; in particular, “when compared to normal Italian readers, their scores were as deviant as those of groups of French and English dyslexics as compared to control subjects in their respective countries” (loc 3898). In other words, the absolute impairment Italian dyslexics suffer from is less than that afflicting English or French dyslexics though the relative impairment is the same. Conclusion: there is no underlying difference between these populations despite their very different behaviors. I love these kinds of discoveries, ones that penetrate beneath the surface glare to unpack common features of the underlying mechanisms.
Let me end this post noting one more thing that caught my syntactician’s eye. Chapter 7 is a long discussion of symmetry effects in reading. Dehaene reports on “mirror reading” (where (young) readers/writers “spontaneously confuse left and right”). He attributes this to a basic structural feature of the brain, viz. It encodes a symmetry principle “deeply buried in the structure of our cortex” wherein “[o]ur visual brain assumes that nature is not concerned with left and right…” (loc 4228).
It should be obvious why I found this interesting. The Minimalist Program (MP) has taken the position that grammars care exclusively about hierarchical dependencies, treating left/right linear order as a late addition that arises when hierarchical grammatical structures are sent to the S&M system for articulation. It is curious do find out that the disregard for left/right order is a design feature of certain parts of the nervous system. Specifically, Dehaene recounts the following accepted wisdom: the visual system has two main networks, a ventral what system, which functions to “recognize and label objects,” and a dorsal how system that does things (executes actions) with the objects so identified. Distinguishing left from right, Dehaene notes, likely arises from the dorsal how system and symmetry is a core feature of the ventral what system.
This dorsal/ventral cut has also made an appearance in the cog-neuro of language. Hickok and Poeppel have relatively recently distinguished a ventral and a dorsal pathway for language, the former mapping sound onto meaning and the latter mapping sound onto articulators (see here). My impressionistic self would love to speculate that FL’s disregard for left/right information is related to its living in a part of the brain that is blind to this kind of information (i.e. maybe the part of FL that maps syntax to meaning (to CI) lives in the ventral stream!). This comports with the basic MP conceit that FL exploits (in part) structures from extant brainware used for other (non-linguistic) cognitive tasks. So, if the FL mapping to “meaning” lives in the symmetrical (ventral) part of the brain (where high level “object recognition” also resides) then the fact that this mapping ignores left/right information (see here) is what we might expect (is this tenous enough for you?). We might also expect linear (left/right) info to be prominent in the dorsal stream, the part of the brain, which maps representations onto articulatory based representations.
Now, all of this is VERY stream of consciousness and as you all know I am far from being competent to do anything more than ramble here (but hey, what’s a blog for!). However, it is neat to have discovered that some parts of the brain, as a matter of fundamental organization (one view: symmetry is “inherent in the geometry of our interhemispheric conncections” (loc 4444)), ignore left/right info and that some parts of the language system, the ones mapping to meaning, appear to live in this general neighborhood.
There’s lots more in the book, and I cannot recommend it highly enough. I will blog one more post in the near future on another topic that Dehaene takes up in the penultimate chapter. But for now, if you have a couple of days of pleasure reading you are looking to fill, reading about reading is a good way to idle away the hours.
 Recycling is the star idea in this book. The term is self-explanatory: cognitive circuits that typically serve one function can be repurposed to serve other ends, an idea congenial to modern day minimalists.
 Dave Kush’s analysis of island violations in Swedish has a similar structure. He noted that the relative unacceptability of island violations was similar in Swedish and English (i.e. the same sentence enjoyed the same relative standing in the two languages), despite the fact that what is deemed ok or ? by speakers of Swedish is considered * by speakers of English. Like Paulesu, Kush has argued that the same mechanisms are at work wrt islands in both grammars despite these absolute differences in acceptability ratings. Of course, why this latter difference exists is well worth exploring (and Kush does) but the important common point is that these easily noticeable differences often mask deeper important commonalities.