Conception or *conceivation? The processing of derivational morphology in semantic dementia

<i>Background</i>: Only a few studies have focused on derivational morphology in semantic dementia (SD). The productive and componential nature of derivational morphology as well as recent findings in psycholinguistics suggest that semantic cognition would be involved in the production and comprehension of derivational morphemes and derived words. Therefore, participants with SD might present impairment in derivational morphology. <br> <i>Aims</i>: This study aims to specify semantic cognition’s involvement in the production and comprehension of derivational morphemes and morphologically complex words in SD participants. This involvement was considered in relation to the production of morphologically complex words, the comprehension of the meaning conveyed by morphemes, and the capacity to distinguish between words with a real vs. an apparent morphological structure. <br> <i>Methods and Procedures</i>: Ten French-speaking SD participants completed three tasks of derivational morphology. Their performances were compared to those of a group of 20 age-, gender- and education-matched adults without cognitive impairment. <br> <i>Outcomes and Results</i>: Compared with participants of the control group, SD participants had more difficulty producing nouns derived from verbs that follow less-frequent patterns of root allomorphy, while their performance was less affected when they could rely on basic morphological decomposition/composition abilities. Participants with SD also had more difficulties to match derived words and pseudo-words to a definition and to distinguish between pairs of real morphological antonyms and pseudo-morphological non-antonyms. <br> <i>Conclusions</i>: These results support the involvement of semantic cognition in the validation of morpheme combinations and in derivational morpheme representation. Difficulties in the production and comprehension of derived words and derivational morphemes are another of the many consequences of central semantic impairment that characterises SD. More studies are needed to develop tests and further characterise the involvement of semantic cognition in derivational morphology.