Synesthesia in children with difficulties in written language learning.

We tested whether the acquisition of grapheme-color synesthesia during childhood is related to difficulties in written language learning by measuring whether it is more frequent in 79 children receiving speech and language therapy for such difficulties than in the general population of children (1.3%). By using criteria as similar as possible to those used in the reference study (Simner et al., 2009), we did not identify any synesthete (Bayesian 95% credible interval [0, 4.5]% for a flat prior). The odds of the null model (no difference between 0/79 and 1.3%) over alternative models is 28 (Bayes Factor). A higher prevalence of grapheme-color synesthetes among children with learning difficulties is therefore very unlikely, questioning the hypothesis of a link between synesthesia and difficulties in language acquisition. We also describe the difficulty of diagnosing synesthesia in children and discuss the need for new approaches to do so.

Personality profile of child synaesthetes.

Previous research into personality and synaesthesia has focused on adult populations and yielded mixed results. One particular challenge has been to distinguish traits associated with synaesthesia, from traits associated with the ways in which synaesthetes were recruited. In the current study we addressed recruitment issues by testing randomly sampled synaesthetes, and we looked particularly at synaesthesia in childhood. Our child synaesthetes were identified by a screening program across 22 primary schools in the South East of England (n = 3387; children aged 6 to 10 years old). This identified two types of synaesthete (grapheme-colour synaesthesia and sequence-personality synaesthesia), and we tested their personalities using both child-report and parent-report measures. We found strong support for synaesthesia being associated with high Openness to Experience, a personality trait linked to intelligence and creativity. Both synaesthesia subtypes showed this feature, supporting previous research in adults (1-3). We additionally found low Extraversion in grapheme-colour synaesthetes and high Conscientiousness in sequence-personality synaesthetes. We discuss our results with reference to earlier recruitment issues, and as to how perceptual differences such as synaesthesia might link to trait-differences in personality.