Association Between a Standardized Digit-Comparison Task and Reading Comprehension in Japanese Schoolchildren With Adequate Decoding

<title>Abstract</title> <p> Background Reading comprehension is generally considered to depend on decoding and language comprehension. However, some children experience reading comprehension difficulties despite adequate decoding. Whether performance on standardized digit-comparison tasks is associated with reading comprehension in such children remains unclear. The present study aimed to examine the association between performance on standardized Number Comparison tasks and reading comprehension in Japanese schoolchildren with learning difficulties but adequate decoding abilities. Methods This cross-sectional study included 410 elementary schoolchildren with learning difficulties who were referred to a hospital. Children meeting standardized criteria for decoding difficulties were excluded. Reading comprehension was assessed using Reading Sentences 3A and 3B from the Comprehensive Assessment of Reading Domains (CARD). Digit-comparison performance was assessed using Number Comparison I and II, standardized subtests of the Wide-range Assessment of Vision-related Essential Skills (WAVES). Hierarchical multiple regression analyses were performed after controlling for sex, full-scale intelligence quotient (FSIQ), and decoding-related measures. Results Number Comparison I (β = .095, <italic>p</italic> = .048) and Number Comparison II (β = .112, <italic>p</italic> = .022) were significantly associated with Reading Sentences 3B but not with Reading Sentences 3A. These associations remained significant after adjustment for decoding-related measures and FSIQ. The additional explained variance was modest (ΔR² = 0.8–1.1%). Conclusions Performance on standardized digit-comparison tasks was associated with one measure of reading comprehension in Japanese schoolchildren with adequate decoding ability, independent of decoding-related performance and general cognitive ability. Although the observed associations were modest, these findings suggest that standardized digit-comparison tasks may provide complementary information when evaluating reading comprehension difficulties in children without decoding impairments. </p>