An analysis of the critical period effects on deaf individuals focusing on the acquisition of verb argument structure: a preliminary study

Considering the fact that different components of linguistic knowledge are not equally vulnerable, this study investigated the knowledge of argument structure of verbs in a group of deaf Persian speakers, as people who have been deprived of linguistic data during the early years of their childhood that is the critical period of language acquisition.
In this study, the knowledge of verb arguments was examined through two tasks, one written (for 10 verbs) and one pictorial (for 10 verbs), in the two groups of deaf and normal hearing individuals, each of which consisting of 12 participants (6 girls and 6 boys).
The analysis of verb argument structure showed that the number of errors in pictorial tests and recognized verb arguments was not significantly different between the groups. However, the main challenge of the deaf participants was attributed to mapping the arguments of the verb onto syntactic level.
The results showed that linguistic levels are not equally dependent on the successful experience of the critical period. The syntax level was highly affected by the critical period, while concepts like verb arguments had the least vulnerability.