What do we know about individuals who reach near-native levels of proficiency in a foreign language?
Achieving Native-Like Second Language Proficiency (Speaking) by Betty Lou Leaver is a research-based catalogue of factors that would seem to predict ability to reach the highest level of foreign language proficiency and is based on common characteristics shared by more than 200 near-native speakers, identified by self-report, survey, and interviews by master testers. The study, following common thought, expected to find a commonality among the highly proficient language users in age of onset, i.e. that beginning as a child results in higher proficiency. However, that was not the case. Age of onset did not matter much except for naturally correct pronunciation picked up by children (though often that was affected by interlanguage contact that happens in immigrant situations) that had to be acquired with great effort by adult learners. The important characteristic in terms of age of onset did not appear to be child vs adult but (1) whether the learner had been exposed to a multilingu