What is Comprehensible Input?

Instructor: Jesse Richter

Jesse holds two masters, a doctorate and has 15 years of academic experience in areas of education, linguistics, business and science across five continents.

Do you need a quick overview or refresher about comprehensible input? This lesson explains the origin and meaning of the term and provides examples of how to incorporate this theory into classroom practice.

What is Comprehensible Input?

The term 'comprehensible input' refers to language that is intelligible but just a little more advanced than the student's current ability to understand it. This means that the overall message of the language is clear even though some words and grammatical structures might be unfamiliar.

This concept is from one of five hypotheses in linguist Stephen Krashen's theory of second language acquisition developed in the 1980s. According to Krashen, language learning is the process whereby a student actively tries to gain understanding. This is different from language acquisition, which is the process whereby a student naturally (passively) gains understanding. From his research, Krashen explains that comprehensible input is necessary for language acquisition.

The Formula for Comprehensible Input

Krashen summarizes his comprehensible input hypothesis in the simple and elegant expression i+1. Here, the letter i stands for input, which is the student's current language ability level. The '+1' is exposure to slightly more advanced language that leads to acquisition. When we combine both parts of the statement into i+1, we give students a task that is challenging yet achievable.

Comprehensible Input = Input + 1.

The i+1 expression is our key to understanding Krashen's hypothesis. If we are only providing the i level of language exposure to our students, we are not challenging them enough to acquire new language. On the other hand, if we provide i+2, we are giving our students a challenge that is too difficult to achieve. This often leads to frustration, decreased motivation and the desire to simply give up.

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