Comparing the intelligence-reading relationship in gifted and twice-exceptional twin students: A case analysis

This comparative case study examined how WISC-IV cognitive index profiles relate to reading outcomes in two pairs of twins (N = 4; ages 9.17 and 9.50 years). One pair consisted of twice-exceptional (2E) students with giftedness and ADHD, whereas the other comprised gifted twins without an additional diagnosis. Cognitive functioning was assessed using Full Scale IQ (FSIQ) and the WISC-IV indices of Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed. Reading performance was evaluated through reading rate, reading accuracy, and reading comprehension. In both twin pairs, FSIQ was high and relatively similar within pairs (2E: 127-131; gifted: 130-132). However, within-pair divergence was more evident in reading outcomes, particularly in reading rate and accuracy. In the 2E pair, the twins differed by 6.5 words per minute in mean reading rate and by 5 percentage points in mean reading accuracy, whereas the difference in reading comprehension was limited to 1 point. By contrast, the gifted pair showed a more homogeneous reading profile, with a difference of 2.5 words per minute in mean reading rate, 1 percentage point in mean reading accuracy, and no difference in reading comprehension. At the cognitive-profile level, the 2E pair showed relatively lower performance in working memory and processing speed, whereas the gifted pair demonstrated higher scores in these domains. These findings suggest that high general cognitive ability may coexist with variability in reading outcomes requiring speed and efficiency. By illustrating how closely matched gifted and twice-exceptional twins may show distinct cognitive-reading configurations, the study highlights the value of profile-based assessment for identifying individual strengths and potential support needs.