The processing of input with differential object marking by heritage Spanish speakers

Heritage Spanish speakers and adult immigrant bilinguals listened to wh-questions with the differential object marker a (quién/a quién 'who/whoACC') while their eye movements across four referent pictures were tracked. The heritage speakers were less accurate than the adult immigrants in their verbal responses to the questions, leaving objects unmarked for case at a rate of 18%, but eye movement data suggested that the two groups were similar in their comprehension, with both starting to look at the target picture at the same point in the question and identifying the target sooner with a quién 'whoACC' than with quién 'who' questions.