Understanding metaphors in developmental dyslexia. From eye-tracking to academic text comprehension.

The ability to understand metaphors has often been investigated in neurodevelopmental disorders, but studies devoted to adults with dyslexia are still few and present mixed results: in Griffith (2007) and Cappelli et al. (2018) participants with dyslexia show difficulties in metaphor comprehension tasks, while in Kasirer and Mashal (2017) the group with dyslexia does not differ from controls. The current research project is aimed at providing further insights into how adults with dyslexia understand metaphors. Three psycholinguistic experiments were conducted. In a first eye tracking study based on the Visual Word Paradigm, novel metaphors and corresponding literal sentences were aurally presented in isolation, and participants were asked to select the picture that best corresponded to what they heard. Findings indicated that those with dyslexia are as accurate as controls in interpreting metaphors but need significantly more time to process the figurative meaning (i.e., present longer fixations to the target picture and reaction times). The second study was then aimed at determining whether the identified slowness arises from early stages of metaphor processing, in which the figurative meaning is generated, and the literal components are inhibited. In a task based on the Metaphor Interference Effect paradigm, high and low familiar metaphors and their scrambled counterparts were aurally presented to participants, who were asked to judge whether sentences were literally true or literally false. Findings suggest that individuals with dyslexia are comparable to participants without dyslexia in the early stages of generating and inhibiting the metaphorical meaning, irrespectively of the metaphor familiarity. Thus, difficulties in metaphor comprehension might depend on meaning construction in context rather than online semantic processing. A third study was designed to verify this hypothesis in the case of academic texts, which typically contain a high number of metaphors. A multiple-choice comprehension task revealed that, when reading ability was used as covariate, university students with dyslexia presented significantly lower comprehension scores in texts in the metaphorical condition but not in those in the literal condition. As a conclusion, we suggest that metaphor might not be detrimental per se for individuals with dyslexia, but that inferencing its meaning and integrating it in complex contexts could add a layer of difficulty. Possible alternative ways to use metaphors in the education field are then proposed as future areas of research, building on the strengths of people with dyslexia.