What is CAH and what are the differences between it and CLI? How can some of the concepts talked about in the Chapter (Brown ch 9) be used in the classroom, e.g., error analysis, CLI, Stages of learner language development, fossilization.
CAH is the Contrastive Analysis Hypothesis, or the systematic observation of frequent learner errors, with the idea that all of these errors are based on the contrast between features in L1 and L2. It was developed to begin predicting the specific errors a language learner will make in order to understand the mental processes of the learner and to possibly "cut them off at the pass," in a way, and plan better, more effective L2 instruction based on the type of L1 interference the student would have. CLI, cross-linguistic influence, is what Wardaugh (1970, as cited by Brown) calls a "weak version" of the CAH. So, there is plenty of error analysis, but only as the leaner produces the errors, not BEFORE the errors take place.
CLI also takes into account the fact that L1 interference/transfer/influence is not the only issue going on in language acquisition, and that a number of learner mistakes (self-correctable, like a mental typo) or errors (not self-correctable without help b/c learners do not know these are errors) must, by their very nature, be indicative of some process or stage going on besides L1 influence. There are intralingual (one language) issues as well as interlingual (two or more languages) issues, and the predictions from CAH often fall flat in the face of the errors the students actually make, although both sides (and most language teachers and learners) would agree that it is beneficial to have some familiarity with the L1 to try to support learners well.
I think learner language can be helpful in guiding us to determine where on the continuum of proficiency our learners may be, and perhaps an activity where learners discuss their processes as they develop would be helpful, either through a language survey asking them how they processed the language during a specific task or a think-aloud (while reading) activity. It takes a lot of time that teachers may not have to closely observe these activities, but even if students engage in such activities in pairs or small groups facilitated by the teacher to raise their own metalinguistic awareness, it should help them realize what the sticking points in their learning may be and name the the confusion they are facing in class.
The topic of error analysis is loaded, because it is usually not clear through simple observation what the root cause of the error is, but through such activities as above, we can try to get to the heart of the matter and determine where to go from here. It is important to try to analyze the errors somewhat and to give error feedback, but with most instructional strategies, the best practice is probably to vary the times we give error feedback, the type of error feedback, and the expected response to error feedback so that we may reach all learners, no matter what their learning styles are.