He specializes in second language acquisition, which he investigates on both theoretical and practical levels, using techniques from psycholinguistics, applied linguistics, and cognitive psychology.
He is renowned for his work on second language acquisition and second language teaching, and for writing successful textbooks and popular books about linguistics.
It contains sample databases from within several subfields of communication, including first language acquisition, second language acquisition, conversation analysis, classroom discourse, and aphasic language.
Thus, high self-consciousness and a reluctance to reveal their weaknesses and faults, coupled with feelings of vulnerability could greatly impede second language learning.