Similar to CLT, Tracey D. Terrell's Natural Approach (1970s) is based
on Stephen Krashen's theories of second language acquisition (L2A). Krashen argues that
there is a natural process by which we acquire second languages. All
that is needed is adequate exposure to 'comprehensible input' in
stress-free situations, and the L2 will be acquired in much the same way
as children learn their first language. Krashen draws a distinction
between conscious learning and subconscious acquisition.