Benefits from morphological regularities in dyslexia are task dependent

Are difficulties of individuals with dyslexia (IDDs) reduced or enhanced in tasks where linguistic regularities typically facilitate performance, such as vocabulary acquisition and reading? If impaired short-term memory and poor phonological decoding pose the main impediments to IDDs, then they are expected to compensate for these difficulties with a greater reliance on linguistic regularities, to reduce online load. However, if reduced benefits from regularities pose the main bottleneck, IDDs might benefit less than good readers from regularities in spite of their online difficulties. To test that, we administered two experiments. In a novel paradigm of auditory vocabulary acquisition in Hebrew, novel words were presented either with or without familiar morphological structure. Participants with dyslexia showed a reduced recall benefit from familiar structure as compared with controls. However, their recognition was facilitated by morphological structure and did not significantly differ from controls'. In the second experiment, participants read novel words with and without familiar structure. Benefit from structure familiarity for IDDs was significantly smaller than for controls, in spite of IDDs' greater potential benefit from familiar structure due to their reduced overall accuracy. However, when asked to emphasize speed in reading, structure familiarity was found to be beneficial for IDDs, without compromising accuracy. These results imply that accumulative acquisition of sublexical regularities is less efficient in dyslexia, though in some tasks this knowledge is accessible and beneficial.