No critical period

However, the study conducted under Stanislas Dahaene showed that the ability to read led to an extension of the areas of language and bidirectional communication between spoken and written language networks. Comparison between good readers and illiterate adults is illustrative of this: in the former, the vision of a written phrase activates the whole area of spoken language, but in addition, hearing a word re-activates its orthographic code in the visual areas. In illiterate adults, on the other hand, language processing is limited to the auditory mechanism alone.

Another interesting result is that the visual area of the left hemisphere which readers use to decode written words is activated in illiterate people when recognising objects and faces. Readers also do this, but the intensity with which the area is activated decreases slightly as their reading ability increases. Thus, activations associated with the recognition of objects and faces are observed as partially moving to the right hemisphere. To summarise, readers' visual corteces reorganise themselves to respond to the new activity of reading, which seems to create competition with the more ancient activities of identifying objects and faces. Does this damage the ability to recognise these two entities? In particular, are people who know how to read less physiognomist than those who don't? We don't currently know.

One questions is particularly pressing: to what extent do the results obtained differ according to whether the ability to read is acquired during childhood or later, through adult literacy classes?  According to the authors of the article published in Science, there is no critical period for learning to read, and the effect of learning upon cortical functioning is almost identical for those who were educated in childhood and those who learned to read later in life. The authors conclude from this, happily, that the circuits involved in reading remain flexible throughout life.

A decoding exercise

Reading is certainly a complex cognitive operation, during which information is transferred from the visual module, enabling the visual perception of words, to the module dedicated to the spoken language. Thus, as Martine Poncelet, researcher in the Psychology, Cognition and Behaviour Department of the University of Liège (ULg) points out, reading may be conducted either through a process of converting graphemes into phonemes, called the 'decoding procedure', or through an overarching process called the 'direct access  procedure'.

Young children who do not know how to read or write recognise certain symbols, which point them towards identifying product brands, for example, or certain simple words which they perceive around them using their visual characteristics. Thus, in French the word 'moto' (meaning 'motorbike') may, because of the two 'o's which appear in it, suggest the idea of two wheels. However, when children start to learn to read, they use the decoding procedure. They undertake a decoding exercise which enables them to establish a connection between the graphemes and corresponding phonemes. This same technique is used by illiterate adults when confronted with new words, some proper nouns or invented words used by psychologists for experimental purposes (pseudo-words). 'According to current thinking about learning written language, the ability to apply the strategy of converting graphemes into phonemes is a necessary condition for good reading', says Poncelet. The task of decoding is indispensable. '

Apart from examples where a word like 'moto' is identified because of its visual particularities, the direct access process only takes place at a subsequent stage. Clearly, it can only achieve be fully utilised by building upon knowledge previously acquired using the decoding process. When a word which has already been decoded is encountered repeatedly within a relatively short period of time, it becomes integrated in the reader's memory, in such a way that its recognition usually becomes instant when they see it. For experienced readers, reading is therefore based upon the direct access pro procedure; the decoding process is only, in theory, used to decipher unknown or forgotten words. 'A good reader is someone who automatically, quickly and faultlessly identifies written words and who can therefore focus on the meaning of what he or she is reading', stresses Poncelet.