Flickering lenses enhance reading performance through placebo effect.

Developmental dyslexia (DD) is the most frequent neurodevelopmental disorder among school-age children. Traditional remediation programs for DD are rarely controlled for the placebo effect, raising the hypothesis that positive expectations might explain their efficacy. Wearing expensive flickering glasses has been associated with extraordinary improvements in reading skills. The placebo effect and efficacy of these glasses on reading performance were tested. A double blind within-subject experimental design was used in children with DD (n = 49; Experiment 1) and unselected young adults (n = 48; Experiment 2). Positive expectancy (placebo effect) improved word reading accuracy in young children with DD, with an effect size larger than those reported for gold-standard training programs. This improvement in reading accuracy was replicated in adult poor readers; whereas typical readers improved only in pseudoword decoding speed. Individually-tuned flickering glasses decreased the advantage of word reading over pseudoword reading (the lexicality effect) and predicted pseudoword decoding speed in children with DD. These findings cast shadows on the real efficacy of dyslexia standard training and highlight how the role of placebo effect in training for DD could be dramatically underestimated.