Contrastive Analysis (= CA) In the 1940s to 1960s before the SLA field as we know it was established, Charles Fries (1945:9) wrote: "The most efficient materials are those that are based upon a scientific description of the language to be learned, carefully compared with a parallel description of the native language of the learner." Robert Lado, Linguistics Across Cultures, 1957: "Individuals t...