Beyond the scope of acquisition: a novel perspective on the isomorphism effect from Broca’s aphasia

Children have been reported to prefer the surface scope or “isomorphic” reading of scopally ambiguous sentences (Musolino 1998, among others). Existing accounts in the literature differ with respect to the proposed source of this isomorphism effect. Some accounts are based on learnability considerations (e.g., Moscati & Crain 2014), while others invoke pragmatic and/or processing factors (e.g., Gualmini et al. 2008; Musolino & Lidz 2006). The present study investigates whether the isomorphism effect is specific to development or rather is observable in other populations with language processing limitations. We investigated the interpretation of ambiguous sentences containing “every” and negation in 4–6-year-old children, individuals with Broca’s aphasia, and neurotypical adult controls. We observed parallel performance in the children and the aphasic group, with both groups accessing more surface scope readings than inverse scope readings. This finding suggests that the preference for isomorphism may not be specific to acquisition and supports accounts that are not specifically based on learnability considerations—for example, processing accounts along the lines of Musolino & Lidz (2006).