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Emmanuel Ahr



Ph.D student

Paris Descartes University

Development of the inhibitory control of irrelevant heuristic strategies : the case of reversible letters b, d, p, and q confusions

Supervised by Grégoire Borst & Olivier Houdé


Every child aged four to seven is likely to commit confusion errors on reversible characters, whose mirror-image counterpart is another character in the writing system (for instance, b, d, p, and q in the Latin alphabet). These errors are produced by the mirror generalization process, a property of the visual system that initially allows us to recognize a face, an animal, or an object independently of the perceived profile. It automatically applies (it is said to be heuristic) to reading and writing. We actually mobilize part of the neuronal networks initially allotted to the visual processing of faces, animals, and objects for learning to read and write, thanks to a process of brain plasticity called neuronal recycling. Thus, reading and writing inherits the mirror generalization property, although it is irrelevant for the recognition of reversible letters b, d, p, and q. Around seven years of age, the frequency of errors of reversible letters confusions suddenly drops. The main objective of the present thesis is to test the hypothesis that the mirror generalization process is not entirely "unlearned" as hypothesized by previous studies but rather actively inhibited. To this aim, we designed negative priming paradigms that we proposed to literate adults and primary school children in four empirical studies. A fifth study, more theoretical, proposes a new law of learning recent cultural objects (written language, mathematics), based on the dual process of "neuronal recycling + inhibitory control".


Brault Foisy, L., Ahr, E., Sarrasin, J. B., Potvin, P., Houdé, O., Masson, S., & Borst, G. (2021). Inhibitory control and the understanding of buoyancy from childhood to adulthood. Journal of Experimental Child Psychology, 208, 105155.

Ahr, E., Houdé, O., & Borst, G. (2018). Behavioral evidence of the inhibition of mirror generalization for reversible letters at a perceptual stage of processing. Annee Psychologique, 118(3), 255-272.


Brault Foisy, L.-M., Ahr, E., Masson, S., Houdé, O., & Borst, G. (2017). Is inhibitory control involved in discriminating pseudowords that contain the reversible letters b and d? Journal of Experimental Child Psychology, 162, 259-267.

Ahr, E., Houdé, O., & Borst, G. (2017). Predominance of lateral over vertical mirror errors in reading: A case for neuronal recycling and inhibition. Brain and Cognition, 116, 1-8.

Ahr, E. (2017) Développement du contrôle inhibiteur de stratégies heuristiques non pertinentes : Le cas des erreurs de confusion des lettres réversibles b, d, p, et q. [Doctoral dissertation, Université Paris Descartes]

Ahr, E., Houdé, O., Borst, G. (2016). Inhibition of the mirror-generalization process in reading in school-aged children. Journal of Experimental Child Psychology, 145, 157-165.

Borst, G., Cachia, A., Tissier, C., Ahr, E., Simon, G., Houdé, O. (2016). Early cerebral constraints on reading skills of school-age children: An MRI study. Mind, Brain Education, 10, 47-54.

Ahr, E., Borst, G., Houdé, O. (2016). The learning brain: Neuronal recycling and inhibition. Zeitschrift für experimentelle Psychologie, 224(4), 277–285. doi: 10.1027/2151-2604/a000263

Borst, G., Ahr, E., Roell, M., & Houdé, O. (2015). The cost of blocking the mirror generalization process in reading: Evidence for the role of inhibitory control in discriminating letters with lateral mirror- image counterparts. Psychonomic Bulletin Review, 22, 228-234.

Brault Foisy, L.-M., Ahr, E., Masson, S., Borst, G., Houdé, O. (2015). Blocking our brain: When we need to inhibit repetitive mistakes! Frontiers for Young Minds. doi:10.3389/frym.2015.00017

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