There is one main principle that governs language growth. It regulates the development of “external language” as a shared social system as well as the development of “internal language” that the individual uses as a means of thought and available output for communication. The principle is so fundamental—like the Law of Gravity—that we seldom notice it. This is the principle of contrast: “A new form emerges in a linguistic system only if it provides a significant contrast with a form that’s already in the system.
I first learned of this principle from Eve Clark, way back when I was at the University of Michigan, in a course I took on child language development. The principle of contrast applies to all language systems—phonological, lexical, syntactic, pragmatic—but it is especially interesting in the acquisition of grammar.
Referring to this principle, Professor Clark often spoke of “emergent language.” “What new contrast is emerging in the mind of the learner?” she would ask repeatedly as we studied transcript after transcript of a child interacting with a caretaker.
This type of investigation is guesswork to a large degree, but if you do the analysis often enough, you start to see clues and patterns and systems and stages.
 Clark, E. (1987). The principle of contrast: A constraint on language acquisition. In B. MacWhinney (Ed). Mechanisms of Language Acquisition, 1-33. Mahwah, NJ: Erlbaum.
The role of emergent language
As a caregiver, or as a teacher, I believe it is ultra-important to think this way: What contrasts are emerging in the mind of the learner? What is the learner noticing? We have to continuously remind ourselves that acquisition is a process that is internal to the learner, not an external quality determined by the input itself and not a direct result of our teaching.
Any other form of thinking, such as “how can I best teach the grammar so that my students learn it?” just misses the boat entirely.
Teachers can, of course, assist learners in initiating the acquisition process. In first language acquisition, there is now considerable evidence to suggest that the way caretakers talk to their children certainly influences how rapidly they acquire the language. And for you brain-research loving teachers (like me), there is also growing evidence that the way teachers talk to their students influences their self-understanding and well-being. 
But how about for second language acquisition? Good news here: There is growing evidence that, in L2 settings, teacher-student interactions play a key role in the perceived enjoyment of learning, positive engagement, and in successful learning outcomes for the students.
All of this is part of “positive well-being.” And, fortunately, teachers are increasingly coming to understand the role of promoting well-being in second language learning situations. Particularly in countries with the ongoing pulse of “one-race nationalism,” it is essential for language professionals to address issues of social injustice. The well-being of our students hangs in the balance.
 Kuchirko, Y., Schatz, J., & Fletchert, K., & Tamis-Lemonda-C. (2019). Do, say, learn: the functions of mothers’ speech to infants. Journal of Child Language (1), 1-21.
 Lippold, M., Davis, K, Lawson, K., & McHale, S. (2016). Day-to-day consistency in positive parent-child interactions and youth well-being. Journal of Child and Family Studies 25, 3584-3592
 Lavy, S., & Naama-Ghanayim, E. (2020). Why care about caring? Linking teachers’ caring and sense of meaning at work with students’ self-esteem, well-being, and school engagement. Teaching and Teacher Education, 91.
 Singer, T. (2017). EL Excellence Every Day. (especially Section 2: Engagement). Thousand Oaks, CA: Sage.
The underlying methodology
Okay, so back to grammar and to the big question of “how.” How do caretakers and teachers accelerate acquisition? Is it osmosis? Is it caring? Is it love? Is it magic? Well, it might be all of those to a degree, but the scientific explanation is actually something much simpler.
Consciously or unconsciously, caretakers use “initiation codes” to draw attention to something in the child’s input (in what the child has just seen or heard or experienced) or in the child’s output (in what the child has just said or done). In other words, they help the learner notice something they had previously been unaware of. And then they let the child do the rest. Internally.
For example, a young child, Amy, age 2, says to her father, as she puts on her coat to go outside with him.
 Greer, A. (2018). Parent-child conversations regarding the movie Finding Dory [Doctoral Thesis]. Salisbury University.
 Foster-Cohen, S. (2013). The communicative competence of young children: A modular approach. (Chapter 4: Communicating with Language). New York, NY: Routledge.
Amy: Amy go Daddy now.
Father: Yes, Amy’s going with Daddy now.
Amy’s father (the teacher) is using an “elaboration statement” (one of the initiation codes) to draw attention to a linguistic contrast that can be discovered. What he is pointing out here to his daughter (the student) is an “overextension.” Overextension is by far the most common type of “grammatical error” in language development. In overextension the learner is overusing one form to govern multiple potential distinctions—here, the unmarked verb “go” governs present “go/goes” and future “is going.” In other words, the learner is not noticing a contrast that the teacher thinks is necessary. Or the learner doesn’t perceive that there is a contrast that can be made.
And that’s okay.
 Kay, A., & Anglin, J. (1982). Overextension and underextension in the child’s expressive and receptive speech, Journal of Child Language, 9, 83–98.
Noticing and pacing
Students learn grammar—learn to perceive contrasts in language they hear and then try out these contrasts in their own speech—at their own pace. Children, in their L1, do it at a steady, comfortable, inexorable rate, in step with their cognitive and social development. No rush, no hurry, it all works out in the end. Teachers and caretakers can and should monitor what is “emerging” in the student’s developmental process. They can create gentle noticing opportunities to accelerate and solidify the student/child’s understanding, but they can’t do the learning. It is the student herself who controls—essentially decides—what to take in.
Or so said Professor Clark. And that was a valuable takeaway for me, as I was about to embark on a career in second language teaching. (My initial training at the University of Michigan was to be a secondary school teacher, but a Peace Corps diversion after my graduation got me re-tracked into second language education.) Teachers can help students to notice a contrast, but it is the student who must do the actual noticing.
am beginning to do language acquisition research. I find myself again with an opportunity to learn from a guru in language acquisition. This time it’s Professor Rod Ellis, the SLA superstar. As luck would have it, we’re sharing an office at Temple University Japan, both teaching in the M.Ed. program. By this time, I’ve become a “specialist” in second language listening. (I define “specialist” as a person who has become obsessed with a certain area of a discipline and doesn’t know how to escape.) And Rod Ellis, of course, has become an international rock star in the grand arena of Second Language Acquisition research, particularly in grammar acquisition.
Through discussions with Rod over the course of the year he was in residence, I became familiar with the vocabulary of his trade: grammar awareness, grammaticality, direct vs. indirect teaching of grammar, consciousness raising tasks, form‐focused instruction, grammar flooding (a focus‐on‐form intervention in which the input that is provided to learners is seeded with multiple examples of a target structure), and a bunch of other “cutting edge” concepts that were relevant to teacher education.
Essentially, what I learned from Rod can be boiled down to a few central points:
- The key question teachers need to ask is: “How can we teach grammar in a way that is compatible with how learners acquire grammar?” We need to teach grammar in a “learner-friendly”—or, more accurately, “learner-accessible”—way.
- When learning a second language, learners need to attend to both meaning and form. (This was at the time Rod’s response to Krashen’s hypothesis that comprehensible input alone is sufficient for learners to acquire grammar.)
- New grammatical features are more likely to be acquired when learners notice and comprehend them in contextualized input than when they engage in extensive production practice focused on specific grammatical points. (This was in response to the debate over whether grammar should be taught “atomistically,” point by point in isolated contexts, or “holistically,” contextualizing target grammar in larger chunks of language. Using contextualized input is also supported by Lightbown’s developing “Transfer-Appropriate Processing” (TAP) Theory about how learners remember new grammar contrasts.)
- Learners’ awareness of grammatical forms helps them to acquire grammatical features slowly and gradually. (This was a defense against the attacks that pointed to little or no effects for “consciousness-raising” (CR) activities in short-term research studies. The claim is that a CR approach helped students become more “grammatical,” leading to better long-term acquisition.)
- The teacher’s role in grammar acquisition is two-fold: (1) providing input (listening or reading) that contains sufficient opportunities for noticing grammatical contrasts that affect meaning; (2) providing opportunities for output (speaking or writing) that force the learner to produce these contrasts in the process of getting their own meaning across. (This was, of course, in response to teachers’ main concern: “The research is all well and good, but what are we supposed to do in the classroom?”)
 Lightbown, P. (2008). Transfer appropriate processing as a model for classroom second language acquisition. In Z. Han (Ed.) Understanding second language process, 27-44. Clevedon, UK: Multilingual Matters
 Ellis, R. (2016). Grammar teaching as consciousness raising. In E. Hinkel (Ed.), Teaching English grammar to speakers of other languages, 128-150. New York, NY: Routledge.
The birth of Impact Grammar
Rod also took an interest in my work on listening strategies, and endorsed my focus on listening-based language acquisition. Shortly after we both left Temple University, we decided to collaborate on a listening-based grammar course. Bringing another former Temple colleague, Steve Gaies, onto the team, we created a course called Impact Grammar: Grammar Through Listening. (This was part of the innovative Impact series, of which I am the series editor, published by Pearson.)
The premise of the course, originally published twenty years ago, was the four points that Rod had been refining up to that time:
- Units are content-based, with the attempt to use topics and genres of interest to the target students, so that “meaning” drives each unit.
- While the units are content-based, the course is also form-focused, with a syllabus of 50 units focusing on 50 grammatical contrasts (e.g. present tense vs. present perfect, definite vs. indefinite article), organized into five levels, based on what was known about “order of acquisition” at the time. (See Taferner, in this issue.)
- Units are input-based and content-driven, with both listening and reading input (typically, classes would read and listen at the same time, though we encouraged listening first). Most critically, the passages were seeded with the grammatical structures we wish to draw attention to. The units are graded according to typical acquisition sequences (what distinctions tend to be learned in what order; see Taferner, in this issue), though this is not an exact science because mastery does not proceed in a clear linear fashion.
Unit activities focus on consciousness-raising and output-oriented tasks, both through comprehension questions and through peer discussions, requiring the students to attempt to recognize and utilize the target grammatical structures (this was referred to internally in the nomenclature of the time as “forced output,” which admittedly sounds a bit brutal!).
A typical unit would flow like this:
Content: A short vignette about a woman who lived at a boarding house.
- Error Box refers to a typical learner error involving the target grammar contrast
- Listening to Comprehend checks general comprehension of the passage.
- Listening to Notice has ten blanks in the passage to be filled in to see if students are noticing the contrast.
- Understanding the Grammar Point requires students to go back to the input passage to formulate rules, followed by an error analysis problem.
- Checking presents (in written form only) a similar passage with ten target contrasts, some of which are correct, some of which are incorrect. Students are asked to identify the errors and correct them.
- Trying It is an expression activity, for speaking or writing exchange, requiring use of the target contrasts.
- Grammar Explanation is a reference table in the appendix articulating the grammar rules and presenting common errors.
Further ruminations… (kind of like post-hoc noticing)
I could end here, as is customary in a teacher-oriented article with a “formula for success.” But, as a course developer, I feel obligated to do a bit of “post-mortem analysis,” to give you a peek at some of the challenges that came up during the process.
Is Impact Grammar a success?
In other words, is an approach to language teaching based on grammatical contrasts and consciousness raising, encapsulated into a text/audio book, a viable path for instruction?
I think you saw this coming: The answer is “yes and no.” Or a mitigated “yes.” Or a theoretical “big success” and a commercial “partial success.”
Theoretically, we were able to demonstrate to teachers and students that there is a coherent approach to teaching grammar based on listening and “noticing.” We demonstrated that we can articulate a classroom approach to learning grammar that is consistent with the research on language acquisition. And we developed a large fan base in the process, a number of teachers who swear by the approach.
Commercially, however, it’s a bit more difficult to call it a success. Clearly, we ran into the “conservative wall” of opposition that limited the sales of the course. Even with proof contrary to their beliefs, most teachers believe that the time-honored PPP (Present-Practice-Produce) approach is the best one to adopt.
The majority of teachers, it would appear, when they are teaching grammar want to have a clear presentation that they are in control of, with a prescribed focus on what is to be learned. They want to have the bulk of class time oriented toward extensive practice and testing of specific points that have been explicitly introduced.
And clearly, the majority of EFL teachers who are teaching limited hours per week will opt for a four-skills course, over a grammar-focused course. That condition too severely limited the size of the potential audience for Impact Grammar in EFL settings.
If I had it all to do over again, would I have pushed for a different version of Impact Grammar, maybe one that appeased the PPP teachers?
First of all, Rod wouldn’t have allowed it. One thing I admire about him is that he sticks to his principles. This “stubbornness” led to a number of uncomfortable, occasionally acrimonious, conversations with my publishing colleagues, some of whom described him as “obstinate” and “difficult to work with.” Publishers do not like to hear an author say, “No, I’m not going to do that because it’s against what I know to be true about language acquisition.” Nor do they want a university professor to “mansplain” how languages must be taught, and hear how they’ve been doing things “backwards” all these years…
But no regrets. I think in publishing (and in other endeavors in life), you undertake some projects as “proof of concept.” You just want to see if something can be done. You want to test out a new dimension of “the principle of contrast.”
So, in conclusion, what have I learned about grammar teaching from this teaching-researching-collaborating–publishing process? Some good stuff, actually. Here are the key lessons that I’ve carried with me to this day:
- Grammar should be taught in context, using full texts (like stories or interviews or movie clips) so that students get used to grammar as a system, not isolated points. Comprehension and output tasks should accompany the input, so that students are required (here’s that “forced output” concept again) to try to use new grammar structures that they normally avoid.
- Students’ grammar development should be evaluated formatively over a long period of time, by the usage in their output, both in speaking and writing. Corrective feedback should be given selectively, and generally as a request for a redo or clarification rather than as error correction.
- “Did you notice…?” should become a frequent question posed to students. Students “become grammatical” by noticing grammar contrasts in use.
- Because grammar is really “the nervous system” of a language, language teachers need to know the grammar of the language they’re teaching inside-out, period. Not that they need to explain rules or give elaborate presentations, but they need to be aware of the contrasts that their students are noticing as they learn the language.
From an instructor’s perspective, the teaching and learning of grammar is a conundrum. How much to present? How much to correct? How much to expect? The answers are not simplistic, but an understanding of the principle of contrast can guide our decision-making.
Michael Rost is an independent scholar, author, editor, and teacher trainer now based in San Francisco. Michael is the author of the several books on oral communication research. He is also editor of several popular online-based and classroom-based learning materials, including Pearson English Interactive, Contemporary Topics, English Firsthand, and Impact Issues, all now in multiple editions.