What is the role of explicit grammatical knowledge in second language acquisition?

“Input cannot be equated with the staple of much traditional language teaching: explanation about grammar, presentation of vocabulary lists, practice, fill-in-the-blanks, and so on. For mental representation to develop, learners have to hear and see language as it is used to express meaning. There are no shortcuts; representation cannot be taught in the traditional sense of teaching.”

—Bill VanPatten, PhD, in ACTFL’s The Language Educator, Oct/Nov 2014

“Conscious learning has an extremely limited function in adult second language performance, it can only be used as a monitor, or editor.”

—Stephen Krashen, PhD, The Natural Approach (1998). p. 30

“Language is best taught when it is being used to transmit messages, not when it is explicitly taught for conscious learning.”

—Stephen Krashen, PhD, The Natural Approach (1998). p. 55

“Comprehensible input, if there is enough of it, automatically contains the grammar that students are ready to acquire.”

—Stephen Krashen, PhD, Fundamentals of Language Education (1992), p. 26