As master language teacher and learner Terry Waltz has beautifully pointed out in this article, it is not enough for the language we deliver to our students (in speech or writing) to be comprehensible. “Comprehensible” is an abstract term, and implies that students “should” understand something. By making “comprehended input” our goal, teachers can plan input with their specific students in mind, rather than a hypothetical or ideal student. Ultimately, we cannot say that the input we provide for our students is comprehensible, until students have shown us that they have comprehended it.
But why would teachers not want the input to be immediately comprehensible (and therefore comprehended) by all of their students? Waltz goes into detail about the educational trends and tendencies which counteract comprehensibility, such as grit, problem-solving, dealing with ambiguity, etc. These skills may be appropriate to other academic subjects, but not the first years of learning a language. As Stephen Krashen has pointed out here, the “no pain no gain” model has no place in language education. So why should our language classes be anything but easy and pleasurable, allowing students to focus on the messages being conveyed rather than the obscure mechanics of grammar for its own sake? Maybe it’s the pride that we and some of our students take in knowing something that not everyone can learn. Maybe it’s the respect we get from colleagues and the larger community for teaching a challenging subject, one which demands rigor and discipline. Again, here’s the link to the excellent article by Terry Waltz:
http://terrywaltz.com/comprehensible-input-blog/c-is-for-comprehended/