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Krashen's Hypotheses and Second Language Acquisition

Krashen's Hypotheses and Second Language Acquisition | ITTT | TEFL Blog

During the previous century, there were many different discussions on second language learning. Hence, many theories were formed by different researchers. The most famous hypothesis was proposed by an American linguist Steven Krashen.

Nature vs Nurture

Researchers have divided second language acquisition into two categories: nurture and nature.

The former proposes that human interaction with the environment leads to experience which results in the acquisition of human knowledge including second language acquisition. The one perspective that is based on nurture doctrine is the behaviorist perspective.

The latter stresses the importance of genetic factors which are also important in second language acquisition. Social science theories explain that knowledge is innate and transmitted genetically. The representatives of this approach believe that humans are born with a device that allows them to learn a language naturally and that learning a language is biologically determined.

Krashen’s Hypothesis

Acquisition or learning

Krashen argues that adult learners develop second language competence through one or two ways which are referred to as acquisition or learning.

Krashen described acquisition as a subconscious process that is similar to the way children learn their second language. In contrast to that, conscious learning is more related to knowing the rules and grammar of the language.

Krashen’s Natural Approach

Krashen's natural approach consists of five main hypotheses:

  1. the acquisition language hypothesis;
  2. the monitor hypothesis;
  3. the natural order hypothesis;
  4. the input hypothesis; and
  5. the affective-filter hypothesis.

According to Krashen, acquisition is a subconscious process whereas learning is conscious.

The monitor hypothesis makes a distinction between acquisition and learning. He said that the learned system acts as a monitor, making changes and polishing what the acquired system has produced.

Krashen's order hypothesis says that second language learners acquire rules of language in a predictable sequence. This hypothesis also states that some rules are easy to memorize and these rules are difficult to acquire.

Krashen's most important hypothesis is the input hypothesis which proposes that the acquirer must receive comprehensible input through hearing, and reading language structures that are above the learners' current ability. It is crucial that the learner receive input that is challenging for them in order for it to lead to improvement in linguistic competence. It is essential to occupy the classroom time with acquisition tasks or activities. Also, the acquirer must not be forced to speak too early.

According to Krashen, learners will go through a silent period when they gradually receive and build enough comprehensible input in order to produce their own structures. That input will occur when the acquirer's affective filter is down or low. This hypothesis received a lot of support.

Even though it had a lot of support, Krashen's hypothesis was faced with some criticism. His monitor theory was attacked because it did not provide clear evidence to show us 'monitor' use. He also has not produced any clear, empirical evidence that more output results in more language acquisition. Moreover, scholars said that they needed clear definitions of acquisition and learning. Many scholars view foreigner-talk (FT) as ungrammatical and are concerned that students may complain if teachers speak to them using modified speech.

Grammatical FT has been seen as useful in supplying simple input. It is widely believed that second language learners need exposure to a broad range of input in order to increase their communicative competence.

Krashen also argues that error collection has no point in long-term linguistic competence. Finally, there is some concern that input does not last long enough to promote the development of confidence in the acquirer and we have no evidence indicating what the acquirer does with the input.

Despite this criticism, Krashen's hypothesis has been popular with many people teaching in the ESL field. He believed that grammar should not be taught in the classroom and that formal rules are not necessary for comprehensible input. Many language instructors supported this. It is also important for instructors to encourage learners to use context and their knowledge of the world to help their learners with comprehension, grammar, and vocabulary. Krashen also found communicative tasks very important. However, some learners, especially adults can benefit from knowing certain rules of grammar and vocabulary explanations. Kreshen also felt that in order to improve their language skills, learners must attempt to understand the language which exceeds their current ability.

Many instructors were very happy with the affective-filter hypothesis and strive to make their classrooms more relaxed and lessons more enjoyable. Also, the input hypothesis can be viewed as too simple as it is not specific enough, but in an overall sense, it is an interesting theoretical perspective.


Despite his theories and hypotheses being criticized and denied by many, Krashen’s hypothesis is still one of the dominant ones in the sphere of second language acquisition. For that reason, it is very important to understand it and try to apply it when learning a second language.

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References:1 Ellis, Rod. 2015. Understanding L2 Acquisition, 2nd ed. Ch. 1 (pp. 16-32)2 Shannon, Frederick. 2012. The Natural Approach: Krashen's Model of Second Language Acquisition. Studies in English Language and Literature, No 62:51-59.