“…Although it is not always the case that heritage speaker (HS) bilinguals differ from monolinguals of comparative ages (see, e.g., Kupisch and Rothman 2016), HS deviation from monolingual performances on experimental tasks-potentially representing bona fide differences in mental grammars-is not uncommon (see, e.g., Montrul 2008Montrul , 2016. It is important to define what we mean by HSs from the beginning.…”