The Audio-Lingual method started in the 1940s as language training for World War II troops, who needed quick training for basic communication. The technique was broadened and popularized in the 50s and 60s and is still used today, mostly in combination with other methods. Drawing on the theories of American linguists Leonard Bloomfield and Charles Fries, the method is based on behaviorism, or giving a stimulus and response which immediately conveys positive or negative feedback. In the case of language learning, the teacher makes a statement that students repeat. The teacher then offers new vocabulary to drill in the same format. Sound Pavlovian? It most certainly is.
Teacher: They like to eat peaches. repeat
Students: They like to eat peaches.
Students: They like to eat pears.
Teacher: I like...
Students: I like to eat pears.
The method relies on drilling, habit formulation, and the use of a language lab, which might remind you of your high school language class. Grammar is not taught outright, but instead language is taught in its correct grammatical structure. Although the method made sense for its original purpose and was successful in allowing basic communication, it has been heavily criticized, especially by linguist Noam Chomsky. The rigidity of the method left little room for the spontaneity of free-flowing conversation, which made it difficult to use the language in the real world.