Contrastive Analysis Hypothesis

1950s and 60s saw language as a habit. Second language learning was seen as forming a new set of habits. Therefore, native language had a very relevant role, since in this view of language learning, it was the major cause of lack of success in language learning. The habits established in childhood (NL) interfered with the establishment of a new set of habits (TL). From this understanding emerged the need to compare NL and TL. This is known as Contrastive Analysis which compares the rules of two languages to determine similarities and differences. Robert Lado is the major proponent of the this field.

Contrastive Analysis (CA) is a way of comparing languages in order to determine potential errors to isolate what needs to be learned and what doesn't need not be learned in second language learning. Phonology, morphology, syntax, social aspects, etc. are studied to predict what will be easier and difficult for learners. Similar structures will be easily transferred and learned.

Lado says:

Since even languages as closely related as German and English differ significantly in the form, meaning, and distribution of their grammatical structures, and since the learner tends to transfer the habits of his native language structure to the foreign language, we have here the major source of difficulty or ease in learning the structure of a foreign language. Those structures that are similar will be easy to learn because they will be transferred and may function satisfactorily in the foreign language. Those structures that are different will be difficult because when transferred they will not function satisfactorily in the foreign language and will therefore have to be changed. (Lado, 59) 

Pedagogical materials that came out of CA in North American tradition were based on the following assumptions:

1. CA is based on the assumption that language is a habit, learning a new language is establisment of a new set of habits. 
2. major source of error in second language is the native language - NL.
3. errors can be explained using differences between NL and TL.
4. Greater the difference, greater the difficulty. 
5. One has to learn the differences. Similarities are easily transferred.
6. difficulty and ease are proportional to differences and similarities between the two languages under consideration. 

Various views on CA Hypothesis

Strong/a priori/predictive view: One can predict about learning, and success of materials based on CA. 

Weak/a posteriori/explanatory view: Starts with the learners' recurring errors and gives explanations for the learner behaviour based on CA.

Weak version gained faith because the strong version failed. Weak version gave importance to the learner, the forms they produced and the strategies they used to reach their IL forms.

CA did not survive because its theoretical background-behaviourims- belief that NL was the driving force of L2 learning- was discarded. In the 60s, language came to be seen in terms of structured rules. Behaviourism was discarded. Learning was no more seen as imitation and habit formation, but as active rule formation. 

The failure of behaviourism had implication on SLA. If imitation and reinforcement has no bearing on NL acquisition, may be SL also is not influenced by it. This became evident through data analysis. Some errors learners produced in L2 were in no way related to the structures/errors in their L1. (He comed yesterday- attempt to impose regularity on irregular verb). The theory did not predict what was happening in non-native speech. Not only did the predictions NOT come true, things that they did not predict appeared more than often. Within a theory based on the transference of NL forms, this could not be explained, for why should transfer occur in one instance, but not in another?

For example:

In French, object pronouns precede the verb, as in 

- Je  les  vois.

  I  them see

 "I see them.”

In English, object pronouns follow the verb. However, the following facts emerge in learner data:

By French learners of English 

I see them. (produced) 

*I them see. (not produced) 

By English learners of French- None of these is possible in French. 

a. Je vois elle. I see her. 

b. Le chien a mangé les. The dog has eaten them. 

c. Il veut les encore. He wants them still. 

In other words, French learners of English never prepose the object pronoun. Rather, they correctly follow English word order, which in this case is in violation of French word order. With English speakers, the reverse occurs: they follow the native language word order. If the “habits” of one’s native language are the driving force, then why should they be operative in one language, but not the other? (Gass 98-99)

The ideas of difficulty were also questioned. Difficulty was equated to errors in CA. Error meant that learner was having difficulty in learning. It is not a real measure of difficulty. How does one judge what is difficult for the learner? Error is not a real measure of difficulty. To equate difference with difficulty attributes a psycholinguistic explanation to a linguistic description. 

We can't say that there are no factors in NL that influences TL. But there surely are other factors than NL. The conclusion is that the 1:1 correspondence implied by CA Hypothesis between native and second language does not hold ground. It is not that simple. L1 has its effect, but cannot be limited to difficulty and transfer. There are other factors that may influence the process of acquisition, such as innate principles of language, attitude, motivation, aptitude, age, other languages known, and so forth. 

Comparing languages is a complex business. Lado himself had identified it. Stockwell, Bowen, and Martin gives a framework or hierarchy of difficulty in learning. it speaks also about ways in which languages can differ. Categories in which there is differentiation (NL has one form, TL has two forms), absence of some category in either languages (articles in English; Japanese has no articles), Only one form in L2, but two in L1, Correspondence, etc. are the elements of the hierarchy. CA also failed to validate claims through data from real world (empirical basis). 

Lado's hypothesis inspired a lot of research in the field of second language learning (to match CA predictions and actual data). As a result of Lado's warning to check hypothesis against actual data, Error Analysis emerged.

Reference
Gass, Susan M. (2008). Second Language Acquisition. Routledge, New York.
Secondary: Lado, R. (1957). Linguistics Across Cultures. Ann Arbor: University of Michigan Press.