Writing is one of the cultural inventions that have radically altered the cognitive skills of the human species. A veritable extension of our memory, it "enables us to converse with the dead, with those who are absent, with those who were never born, across all distances of time and space" (Abraham Lincoln). The aim of the 2006-2007 lecture was to examine the mechanisms that enable the human brain to read, i.e. to access linguistic and memory representations through the visual recognition of arbitrary symbols.
The cognitive mechanisms of reading are of particular interest insofar as they raise the question of the foundations of cultural learning. Writing was only invented some 5,400 years ago, and until very recently, only a tiny fraction of humanity learned to read. So there's no way the human brain could have been selectively pressurized in the course of its evolution to facilitate learning. The same is true of most, if not all, of the cultural skills that are part of humanity's recent baggage: at first glance, they seem unprecedented in the evolution of species and detached from any link with the evolutionary history of our brains. Indeed, very few social scientists consider that brain biology and evolutionary theory could be relevant to their field of study. Most adhere to an implicit model of the brain that I call generalized plasticity and cultural relativism, which sees the human brain as a universal learning device. Freed from the shackles of biology, the human brain, unlike that of other animal species, would be capable of absorbing any form of culture, however varied.
In contrast to this dualistic, relativistic vision, which dissociates human thought from its biological roots, the 2006-2007 lecture, through a detailed examination of the brain's mechanisms of reading, set out to outline a neurobiological approach to human cultural activities, the theory of neural recycling. Clearly, this is not to deny that our brains are capable of learning, without which they would never be able to incorporate new cultural objects. But this learning seems to be narrowly limited. In all individuals, in all cultures of the world, the same brain regions are involved in reading, and the same constraints characterize writing systems. According to the neural recycling hypothesis, cultural inventions such as reading are based on ancient brain mechanisms that have evolved for a different purpose, but which have sufficient plasticity to be able to recycle or reconvert to this new use. Each cultural object must therefore find its "ecological niche" in the brain: a circuit whose initial role is sufficiently similar, and whose flexibility is such that it can be reconverted to this new use. However, this circuit retains intrinsic properties, inherited from its evolutionary history, which make it more or less suitable for its new purpose. Neurobiological constraints thus confer universal traits on cultural objects.
In the case of reading, three major sets of brain circuits are involved. The networks of invariant visual recognition are involved in identifying the string of characters - these are the circuits that are best known at the cerebral level today, and to which the neural recycling model applies most directly. Next comes the conversion of written characters into a phonological representation and, in parallel, access to the lexicon and meaning of words and sentences. Each of these networks is put in place with the learning to read, depends in part on the organization of writing and the orthography of the language, and can be the subject of cognitive deficits in both adults and children. The lecture successively examined these different points, drawing on specialized literature as well as several reference works (Ferrand, 2001; Rayner & Pollatsek, 1989; Snowling, 2000; Snowling & Hulme, 2005).