title: Literacy breaks mirror invariance for visual stimuli: a behavioral study with adult illiterates.
abstract: The ability to recognize 2 mirror images as the same picture across left-right inversions exists early on in humans and other primates. In order to learn to read, however, one must discriminate the left-right orientation of letters and distinguish, for instance, b from d. We therefore reasoned that literacy may entail a loss of mirror invariance. To evaluate this hypothesis, we asked adult literates, illiterates, and ex-illiterates to perform a speeded same-different task with letter strings, false fonts, and pictures regardless of their orientation (i.e., they had to respond "same" to mirror pairs such as "iblo oldi"). Literates presented clear difficulties with mirror invariance. This "mirror cost" effect was strongest with letter strings, but crucially, it was also observed with false fonts and even with pictures. In contrast, illiterates did not present any cost for mirror pairs. Interestingly, subjects who learned to read as adults also exhibited a mirror cost, suggesting that modest reading practice, late in life, can suffice to break mirror invariance.
authors.affiliation: Cognitive Neuroimaging Unit, INSERM-CEA.
authors.forename: Felipe
authors.initials: F
authors.lastname: Pegado
authors.affiliation: Collège de France.
authors.forename: Kimihiro
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: SARAH Hospital.
authors.forename: Lucia W
authors.initials: LW
authors.lastname: Braga
authors.affiliation: Faculty of Psychology, University of Lisbon.
authors.forename: Paulo
authors.initials: P
authors.lastname: Ventura
authors.affiliation: SARAH Hospital.
authors.forename: Gilberto
authors.initials: G
authors.lastname: Nunes Filho
authors.affiliation: Cognitive Neuroimaging Unit, INSERM-CEA.
authors.forename: Christophe
authors.initials: C
authors.lastname: Pallier
authors.affiliation: Cognitive Neuroimaging Unit, INSERM-CEA.
authors.forename: Antoinette
authors.initials: A
authors.lastname: Jobert
authors.affiliation: Faculty of Psychology, Université Libre de Bruxelles.
authors.forename: José
authors.initials: J
authors.lastname: Morais
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, Université Pierre et Marie Curie-Paris.
authors.forename: Laurent
authors.initials: L
authors.lastname: Cohen
authors.affiliation: Faculty of Psychology, Université Libre de Bruxelles.
authors.forename: Régine
authors.initials: R
authors.lastname: Kolinsky
authors.affiliation: Collège de France.
authors.forename: Stanislas
authors.initials: S
authors.lastname: Dehaene
mesh_terms: D000328:Adult; D004522:Educational Status; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation; D011930:Reaction Time; D017603:Signal Detection, Psychological; D055815:Young Adult