In his work on the “Natural Approach", linguist and researcher Stephen D. Krashen and Spanish teacher Terry Terrell offer five hypotheses linked to second language acquisition. These five hypotheses help to offer some insight as to the operating processes of learning a second or foreign language. The five hypotheses are:
- The Input Hypothesis
- The Affective Filter Hypothesis
- The Acquisition – Learning Hypothesis
- The Natural Order Hypothesis
- The Monitor Hypothesis
Using these hypotheses, we can address different ways in which people of different ages, backgrounds, socio-economic levels and intrinsic or extrinsic motivations internalize a first, second or foreign language. Briefly then, let’s look at each and how it generally applies to second language acquisition.
The Input Hypothesis
This hypothesis of Stephen D. Krashen states that language is acquired through the understanding of input, which is just a bit past our existing level of language ability. By understanding a piece of language structure that is a part of the next step in our language learning process, we develop increased competence in a language. For example, if a learner hears the “–ed" suffix on the end of a verb used in simple past tense and understands that past tense is indicated, the learner progresses to the stage of internalizing the elements of the simple past tense. Through a progressive series of inputs, a learner moves through stages of learning a language.
The Affective Filter Hypothesis
This hypothesis states that how “open" or receptive a learner is to language input or stimulus is determined by mental screening of language elements. That is to say when learners are highly receptive to language input as with using songs, for example, with musical-rhythmic intelligence learners, language learning takes place faster, more effectively and at a deeper level than when an alternative approach less amenable to the learner is used. With a musical-rhythmic learner as mentioned earlier, a purely verbal-linguistic approach may be far less successful since the learner may well “filter out" language input using this approach.
The Acquisition – Learning Hypothesis
The acquisition-learning hypothesis of Stephen D. Krashen and Tracy D.Terrell (1983) states that when language is used for actual communication purposes, it is in effect, acquired language. When formal study of a language is undertaken, the language is then “learned" as opposed to being acquired as defined above. Total immersion in a language and related culture then results in language acquisition, whereas taking university or language school courses in grammar, writing or otherwise learning about the language results in language learning.
The Natural Order Hypothesis
This hypothesis states that language or linguistic structures tend to be learned naturally in a relatively predictable order. So some structures tend to be learned very early in the language learning process, while other more complex or difficult structures tend to be learned much later in the overall language learning process. Present tense, present continuous and simple past tense, for instance, will be learned by most language students much earlier than say, the present perfect continuous, present perfect or future perfect continuous verb tenses among other grammatical structures.
The Monitor Hypothesis
The monitor hypothesis helps to explain why adult language learners tend to over-extend the “silent period" of language learning, during which speech and language output are minimal, since they tend to monitor their language speech, writing and output until they feel it is going to be “perfect." Learners tend to think about language or grammar rules, correctness and form before giving output or engaging in speech. They will even monitor their language to the point that they might even interrupt what they are saying in order to ask about rules, correctness, vocabulary or form. Children tend to be far less affected by the use of their linguistic monitor in foreign language or second learning than adult learners are.
In addition to these five hypotheses on language learning and language acquisition, certain elements may heavily impact second language acquisition, such as education background. Other factors include:
- The language learning method or approach used
- The age and background of the language learner
- The language learner’s first language and culture
- Time allotted or available for second language learning
- Materials and resources available for second language learning support
The Natural Approach in addition to aspects affected by these five hypotheses can provide some needed insight into the process of second language acquisition. This helps both language learners and language teachers alike to make effective adjustments in the learning process.