Here a quote from Stevick provided by Brian Barabe:
“According to the Natural Approach, adults acquire a language in much the same way as infants do.’ That is to say, they acquire it through exposure to sounds of the language and, simultaneously, to themeanings that go with those sounds.“
Those who say the natural approach or other CI methods assume 2nd language acquisition is done in the same way as the first quote only the first sentence, leaving out the second which shows HOW second language acquisition is the same as the first.