Profile of hyperlexia: Reconciling conflicts through a systematic review and meta-analysis

It is believed that children with poor decoding skills and adequate listening comprehension skills exhibit a dyslexia-type syndrome. However, there is no consensus relating to the other problem that arises: children who have exceptional decoding but poor listening comprehension. Sometimes, these children have been labeled as “individuals exhibiting hyperlexia.” There is no clear understanding of the following aspects of hyperlexia: a) population criteria (e.g., typically vs. atypically developing children), b) specific criteria (e.g., precocity, definition of “good decoding”) on their associations with reading, and c) the applicability of reading theories to hyperlexia (e.g., phonemic awareness is critical in decoding; both decoding and listening comprehension contribute to reading comprehension). Therefore, we conducted a systematic and meta-analytic review to explore these questions. We found that despite good decoding and verbal short-term memory skills, individuals with hyperlexia exhibit poor listening, verbal working memory, and reading comprehension skills. Also, all but three studies identified hyperlexics from atypical developing populations; however, criteria to define “good decoding” varied and the onset of precocious decoding behavior was not consistently reported. Our meta-regression analysis suggests that decoding still predicted the performance of reading comprehension after controlling for listening comprehension, suggesting that the variations of defining “good decoding” led to different reading comprehension profiles (e.g., mild vs. severe reading comprehension deficit). Further, listening comprehension but not decoding is related to phonemic awareness, which may be due to the difficulty of understanding phonemic awareness tasks. However, it may also suggest that the current decoding theory is not applied to hyperlexia. Future suggestions for hyperlexia research are provided.