Revue de neuropsychologie


Does the reversal of the letters and digits by the five- to six-year-old child originate in the computational magic of the ventral stream? Volume 6, issue 4, Octobre-Novembre-Décembre 2014


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Université de Lorraine,
Laboratoire InterPsy,
EA 4432,
3, boulevard Albert-Ier, BP 3397, 54015 Nancy cedex, France
* Correspondance
1 Poggio et al. utilisent cette expression pour signifier que les objectifs computationnels et les propriétés détaillées des cellules de la voie ventrale suivent des propriétés de symétrie du monde visuel [1].

Evolution has certainly contributed to the establishment in our brain of a symmetrization process that helps to identify an object oriented to the left (for example) when we saw it as it was oriented toward the right. This process leads to generalization and is fundamentally adaptive because, for example, a tiger is equally threatening whether it is seen in right profile or left profile. The symmetrization process was recently investigated in the macaque and the human brains, notably through functional resonance magnetic imaging. These investigations support the idea that orientation information is processed in very early visual regions, and leaves open the possibility that this information disappears at subsequent processing stages. In reflecting the development of the symmetrization process, the authors suggest that it should lead to the left-right reversal (also called mirror-writing) of the letters and digits in the young child. Indeed, the process is very efficient until the age of three or four years, but become misleading when the child would write J, Z, and 3 (and not ) for example. An empirical study involving 189 five- to six-year-old children supports the hypothesis that during the time needed for the operationalization of an additional mechanism of orientation's retention, the children direct the characters towards the right (at least in a French culture). As a consequence, children who reverse the left-oriented characters (1, 2, 3, 7, 9, J, Z) the most are also those who reverse the other asymmetrical characters the least. This important result, and also more direct comparison, implies that some individual characteristics of the children, such as left-handedness, gender or the socio-economic level of their parents, explain badly the mirror-writing of capital letters and digits.