Child and adult Spanish heritage speakers have been shown to display erosion and loss of the tense-aspect and mood system in oral production. In particular, While they retain the preterit-imperfect difference in the past, the meanings and forms are often confused. Subjunctive morphology, on the other hand, is even more affected (Silva-Corvalan, 1994 2003). Two related Studies were conducted to examine the extent of incomplete knowledge of tense-aspect and mood morphology in 65 adult Spanish heritage speakers raised in the USA and a comparison group of 23 fully competent adult native speakers. Study I tested the preterit-imperfect contrast with different predicates; Study 2 focused on the present indicative-subjunctive contrast in different Subordinate clauses. Both Studies used elicited oral and written production tasks to test morphological accuracy and a sentence conjunction judgment task to tap semantic Interpretations. The overall results showed significant differences between the native speakers and the heritage speakers, confirming that heritage speakers make errors with grammatical aspect and mood morphology. Accuracy on grammatical aspect, however, is higher than accuracy on sub morphology in oral and written production and interpretation. This result is compatible with the Regression Hypothesis (Jakobson, 1941), which relates order of acquisition to order of language loss, and with the Interfaces Hypothesis (Tsimpli & Sorace, 2006). which takes into account file complexity of certain linguistic interfaces.
