The Case for Comprehension Input

Stephen Krashen provides the evidence to support his hypothesis of second-language acquisition

The work of the last 40 years is the result of a war between two very different views about how we acquire language and develop literacy.

The comprehension hypothesis says that we acquire language when we understand what we hear or read. Our mastery of the individual components of language (“skills“) is the result of getting comprehensible input.

Its rival, the skill-building hypothesis, says that the causality goes in the other direction: we learn language by first learning grammar rules and memorizing vocabulary, we make these rules and new words “automatic” by producing them in speech or writing, and we fine tune our (conscious) knowledge of grammar and vocabulary by having our errors corrected.

In this paper, I briefly present some of the data that support the comprehension hypothesis as well as research that demonstrates the limits of skill building in the area of second-language acquisition.

Evidence for the Comprehension Hypothesis

Comparison of Comprehension-Based Methods and Traditional Methods
When comprehensible-input-based methods are compared to methods that demand the conscious learning of grammar, comprehensible-input methods have never lost.
Krashen (2014a) includes studies of beginning and intermediate language teaching, the latter including content-based (sheltered) instruction and classes that include time set aside for self-selected reading.

Several reviews have confirmed the effectiveness of sheltered subject-matter teaching (Krashen, 1991; Dupuy, 2000) as well as in-class self-selected reading on tests of vocabulary development and reading comprehension (Jeon and Day, 2014; Nakanishi, 2014). Mason ( includes a number of studies showing that CI-based methods, such as hearing interesting stories (story listening) and pleasure reading, are more efficient than “study”—that is, more language is acquired per unit…

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