Effects of age of acquisition on morphosyntactic structures in Turkish sign language: Evidence from classifiers

This study investigates the differences in language production and comprehension of early learner and late learner Turkish Sign Language (TİD) signers. For this purpose, I focus on the complex structures such as classifiers and coordination to find out: (i) whether we observe any differences in the production of classifiers by early learner and late learner TİD signers with respect to morphological encoding as well as overt expression of the arguments on syntax-discourse level, (ii) whether we see any differences in the comprehension of coordinated clauses between two groups regarding the interpretation of the missing argument. I conducted two tasks, a production study with classifier constructions and a comprehension study with coordinated structures. The results of the production study indicate that early learner (Mage = 30) and late learner (Mage = 38) TİD signers encode the thematic role of the argument morphologically in an accurate way; therefore, this aspect of TİD grammar is not age-sensitive. However, the findings on the overt expression of the arguments in classifier construction show two groups utilize different alignment systems, which indicates that this aspect of the language is age-sensitive. The findings of the comprehension task conducted with 20 TİD signers (10 early and 10 late learners; Mage = 31,9 and Mage = 39,3, respectively) confirm the findings of the production study which claims early and late learner TİD signers use different alignment systems. However, no significant effect of thematic roles of the arguments is observed in this task unlike the production study. This finding may indicate the differences between the nature of classifier predicates and plain verbs.