Second language processing (SLP) is an emerging field of research that examines the mental processes involved in language use by non-native speakers. It explores topics such as how non-native speakers’ use of language is affected by their first language, age of acquisition, and L2 proficiency and to what extent they are able to develop nativelike competence in a non-native language. SLP is closely related to cognitive sciences, psycholinguistics, second language acquisition, and applied linguistics. SLP seeks insights in psycholinguistics for theoretical frameworks, language processing phenomena, and research methods. Its findings offer insight on many issues related to second language acquisition and teaching.