Inhibition of the mirror generalization process in reading in school-aged children

• Mirror errors (confusing b for d) in reading are quite common in children.
• Mirror generalization might be at the root of these mirror errors.
• Discriminating ‘b’ from ‘d’ impairs discriminating animals presented in mirror.
• Children must inhibit mirror generalization to avoid mirror errors in reading.

A striking error in reading is the early and sometimes persistent confusion of mirror letters such as b and d. These mirror errors are likely a result of the mirror generalization process that allows one to identify a visual stimulus regardless of its presentation side. A previous study demonstrated that preventing mirror errors in reading requires the inhibition of the mirror generalization process in expert adult readers (Borst et al., 2015). Using the same experimental paradigm, the current study aimed at replicating this result in school-aged children. Three age groups—1st, 3rd, and 5th graders—performed a negative priming study in which they were asked to determine on the primes whether two letters were identical and on the probes whether two animals facing opposite directions were identical. All three groups of children required more time to discriminate two letters that were lateral mirror images of one another (e.g., b/d) than two letters that were not (e.g., f/t). Crucially, children required more time to determine that two animals facing opposite directions were identical when preceded by two letters that were lateral mirror images of one another (b/d) than when preceded by letters that were not mirror images of one another (f/t). Importantly, the amplitude of the negative priming effect did not vary with age. Our results suggest that overcoming mirror errors in reading, regardless of the reading proficiency of school-aged children, is rooted in the ability to inhibit the mirror generalization process.