Not All Comprehensible Input Is Optimal Input

By Beniko Mason

Because we want to help students enjoy language acquisition, we often consider bringing in visual supplements such as puppets, costumes, music, and others. We often think that it is a good idea to praise them to motivate them. But ironically, they often become a hindrance instead.

We have heard that comprehensible input is the cause of language acquisition, but have we considered whether the comprehensible input we provide is what the theory intended? The kind of input that Input Theory claims is sufficient by itself.

Is anything that students can understand and enjoy optimal input that causes optimal results?

Any method contains comprehensible input, but that input may be impoverished, and furthermore, the method may contain learning activities that hinder acquisition.

It is inherently the teacher’s job to make instruction comprehensible. So, almost anything teachers do contains comprehensible input.

When Input Theory stated that the cause of language acquisition is comprehensible input, and that it alone is sufficient, it meant that the input in question was optimal (Krashen, 1982). It was already stated over 40 years ago that comprehensible input had to be interesting, relevant, and abundant.

Over the years, through applying the theory in classrooms, using stories, making language delivery richer through comprehension-aiding supplementation (CAS), increasing the amount of input, and eliminating activities that encourage conscious language learning, Story-Listening gradually developed. More recently, the Input Hypothesis has been clarified as the Optimal Input Hypothesis.

It is a clarification of what Stephen Krashen has consistently argued for many years.

I have introduced the term P.O.U.I. (Pure Optimal Unified Input). The concept of pure optimal input has already appeared in published work co-authored with Stephen Krashen (Smith, Mason, & Krashen, 2021) and is consistent with the Optimal Input Hypothesis (Krashen & Mason, 2020). The term unified emphasizes the integration of Story-Listening and Guided Self-Selected Reading as complementary applications of Input Theory.

The Distinction Between Comprehensible Input and Optimal Input

The distinction between comprehensible input and optimal input is important.

Today, the term “comprehensible input” is often used very broadly. A grammar lesson may contain comprehensible input. A communicative activity may contain comprehensible input. Vocabulary exercises, teacher explanations, reading passages, and even drills may contain comprehensible input. Even theories that emphasize output or interaction often acknowledge the importance of comprehensible input, since interaction with proficient speakers may provide learners with opportunities to receive it.

However, the mere presence of comprehensible input does not necessarily make an activity optimal for acquisition.

When Input Theory claimed that comprehensible input alone was sufficient for acquisition, it was not referring to input embedded within large amounts of conscious learning activities. It was referring to input that learners could understand, attend to, and receive in sufficient quantity.

Many classroom activities divide learners’ attention between meaning and conscious learning. Students may be asked to memorize vocabulary, monitor grammatical accuracy, complete exercises, answer comprehension questions, or produce language before they have acquired enough language to do so comfortably. While such activities may contain some comprehensible input, their primary purpose is conscious learning rather than acquisition. They also consume time and mental resources that could otherwise be devoted to receiving optimal input.

The issue is not whether these activities are good or bad. The issue is whether they contribute to optimal acquisition.

If acquisition occurs through understanding messages, then we should ask a simple question: Does this activity increase optimal input, or does it reduce the amount of optimal input learners receive?

What P.O.U.I. Means

Optimal input has several characteristics. It is comprehensible. It is compelling enough to hold attention. It is rich in natural language. It is abundant both within individual input events and across time. Through comprehension-aiding supplementation (CAS), learners receive more comprehensible instances of familiar language (i), more opportunities to encounter i+1, and exposure to i+n that may serve as future investment for later acquisition. Most importantly, learners can focus primarily on meaning rather than on language itself.

This is the context in which I use the term P.O.U.I.

Pure refers to minimizing interruptions from activities whose primary purpose is conscious learning.

Optimal refers to input that is comprehensible, compelling, rich, and abundant.

Unified refers to the integration of listening and reading as complementary forms of the same acquisition process.

Is P.O.U.I. a New Theory?

No.

P.O.U.I. is not a new theory of language acquisition. It is not intended to replace Input Theory, revise it, modify it, or compete with it.

Rather, it is an attempt to describe more precisely the conditions under which Input Theory operates most effectively. Krashen (2024) has described Story-Listening and Guided Self-Selected Reading as applications of Input Theory.

Unfortunately, over the years, the term “comprehensible input” has sometimes become so broad that it includes almost any activity containing understandable language. When this happens, we may lose sight of the original claim of Input Theory — that acquisition occurs through input and that this input, when optimal, is sufficient.

P.O.U.I. simply emphasizes what was already present in the theory but has become clearer through decades of classroom application and research. In this sense, P.O.U.I. is an attempt to clarify the conditions under which Input Theory operates most effectively.

Many methods contain comprehensible input. The important question is not whether comprehensible input is present. The important question is how much optimal input is present, and how much of it reaches learners without interruption.

If language acquisition is driven by optimal input, then our task is not simply to make language comprehensible. Our task is to provide the richest, most compelling, most abundant, and least obstructed input possible.

Comprehensible input alone is not enough.

What matters is optimal input.

And if we wish to maximize acquisition, we should strive to provide it as purely as possible.

References

Krashen, S. D. (1982). Principles and practices in second language acquisition. New York: Prentice-Hall. http://www.sdkrashen.com/content/books/principles_and_practice.pdf
Krashen, S. (2024). Language acquisition and the power of pleasure reading. Asian Journal on Perspectives in Education, 5(1):19-25. https://www.researchgate.net/publication/395447277_Language_Acquisition_and_the_Power_of_Pleasure_Reading
Krashen, S., & Mason, B. (2020). The optimal input hypothesis: Not all comprehensible input is of equal value. CATESOL Newsletter (May). https://www.catesol.org/v_newsletters/article_151329715.htm
Mason, B., & Krashen, S. (2020). The Promise of “Optimal Input.” Turkish Online Journal of English Language Teaching (TOJELT), 5(3), 146-155. http://beniko-mason.net/content/articles/2020-10-20-revised-the-promise-of-optimal-input.pdf
Smith, K., Mason, B., & Krashen, S. (2021). Story-listening and guided self-selected reading: Short-term results from Indonesia. Language Issues, 1(3), 2–14. https://www.beniko-mason.net/content/articles/2021-short-term-results-from-indonesia.pdf