Masking Dyslexia: Lexical-Semantic Compensation in Twice-Exceptional Children

Children with high intellectual ability may exhibit reading difficulties that remain undetected because their cognitive strengths partially compensate for underlying decoding deficits. Although this masking hypothesis is widely discussed in the literature on twice-exceptionality, the cognitive mechanisms supporting compensation remain poorly understood. Building on cognitive models of reading, we hypothesized that compensation primarily operates through lexical-semantic processing, allowing high-ability children to benefit from meaningful linguistic material while providing little advantage in tasks that require sublexical phonological decoding.
To test this hypothesis, we conducted a retrospective multiple single-case study using clinical data collected from five specialized Italian diagnostic centers. The sample comprised 34 children with high intellectual ability and reading weaknesses (twice-exceptional group) and 51 children with developmental dyslexia and average intellectual functioning. Reading performance was assessed using standardized text, word, and pseudoword reading tasks. Bayesian single-case methods were employed to identify both individual reading deficits and statistically significant dissociations between reading conditions.
Children in the twice-exceptional group showed substantially fewer impairments in text reading than in word reading and, particularly, pseudoword reading. Moreover, they displayed dissociation patterns that were predominantly consistent with relatively preserved lexical-semantic processing and weaker sublexical decoding. In contrast, children with developmental dyslexia exhibited a more generalized and heterogeneous pattern of impairment. Notably, the main differences between groups emerged in comparisons involving pseudoword reading rather than text-versus-word reading, suggesting that compensation reflects enhanced lexical-semantic support rather than contextual facilitation alone.
These findings provide empirical support for theoretical accounts proposing that high cognitive abilities selectively compensate for reading difficulties when semantic information is available. They also highlight the clinical importance of pseudoword reading tasks and multiple single-case analyses for identifying hidden reading difficulties in high-ability children, thereby contributing to more accurate assessment of twice-exceptionality.