We evaluated the contributions of lexical quality (LQ) (Study 1) and ASL variables (Study 2) to reading comprehension in deaf adult signers, matched for reading ability with hearing non-signers. The Lexical Quality (LQ) Hypothesis proposes that the quality of phonological, orthographic, and semantic representations impacts reading comprehension, above and beyond other variables known to influence comprehension, such as non-verbal reasoning, age or education. The LQ variables were orthographic (spelling), phonological, and semantic (vocabulary) knowledge assessed using standardized tests.
In Study 1, we recruited 98 hearing and 97 deaf adults who completed a number of assessment tests, including a standardized test of reading comprehension (PIAT-R reading comprehension subtest). Using a hierarchical regression model, which allows us to factor out variables one step at a time, we found that for hearing readers, phonology was the strongest predictor of reading comprehension. In contrast, for deaf readers, semantics and orthography, not phonology, predicted reading comprehension. We replicated this result using a different test of reading comprehension (assessed by the Woodcock-Johnson IV Passage Comprehension Subtest), suggesting that the lack of the role of phonology is not specific to the PIAT test. We conclude that strong orthographic and semantic representations, rather than precise phonological representations, predict reading skill in deaf adults.
In Study 2, we recruited 89 deaf ASL signers, who completed tests of ASL skill, ASL comprehension, ASL sentence reproduction and ASL fingerspelling repetition tests. We asked to what extent ASL skills predict reading comprehension above and beyond other variables. We found that fingerspelling was the only significant variable in our model, explaining variance in reading comprehension scores. The findings corroborate the idea that ASL fingerspelling and English orthography mutually facilitate reading proficiency in deaf readers .