This document summarizes research on non-native English speakers learning in English. It reviews both psycholinguistic and sociolinguistic studies on bilingual learners. The psycholinguistic studies show that the language used in learning tasks can impact specific cognitive processes, with performance generally better when the language matches what was used during initial learning. However, more abstract tasks may not be affected by language. Sociolinguistic studies reveal important personal and social factors, showing learners strategically switching between languages to facilitate learning. Both types of studies provide insights into how bilingual learners use their multilingual resources to achieve learning goals.