Core Theories and Concepts in Second Language Acquisition

Interlanguage: A Unique Linguistic System

Interlanguage recognizes that L2 learners construct a linguistic system that draws, in part, on the learner’s L1 but is also different from it and also from the target language. It is a unique linguistic system and involves different premises.

Premises of the Interlanguage System

1. Mental Grammar: The learner constructs a system of abstract linguistic rules which underlies comprehension and production of the L2. This system is viewed as a mental grammar.
2. Permeability: The learner’s grammar is permeable. It is open to influence from the outside (e.g., through the input) and also from the inside (omission, overgeneralization, and transfer errors).
3. Transitional Nature: The grammar is transitional. Learners change their grammar from one time to another by adding rules, deleting rules, and restructuring the whole system. This results in an interlanguage continuum.
4. Variability: Researchers have claimed that the systems learners construct contain variable rules. Other researchers argue that interlanguage systems are homogeneous and that variability reflects the mistakes learners make when they try to use their knowledge to communicate.
5. Learning Strategies: Learners employ various learning strategies to develop their interlanguage.
6. Fossilization: The learner's grammar is likely to fossilize. Only 5% of learners go on to develop the same mental grammar as native speakers. The prevalence of backsliding (e.g., the production of errors representing an early stage of development) is typical of fossilized learners.

Behaviorist Learning Theory and Habit Formation

According to this theory, language learning involves habit formation. Habits are formed when learners respond to stimuli in the environment and subsequently have their responses reinforced so that they are remembered. Learning took place when learners had the opportunity to practice making the correct response to a given stimulus. Learners imitated models of correct language and received positive reinforcement if they were correct and negative reinforcement if they were wrong.

It should be clear that behaviorist accounts of L2 acquisition emphasize only what can be directly observed and ignore what goes on in the “black box” of the learner’s mind.

The Mentalist Theory of Language Acquisition

According to the Mentalist Theory:

1. Only human beings are capable of learning language.
2. The human mind is equipped with a faculty for learning language, referred to as a “Language Acquisition Device” (LAD).
3. This faculty is the primary determinant of language acquisition.
4. Input is needed, but only to trigger the operation of the language acquisition device. If learners don’t receive any input at all, they won't be able to activate the language.

Computational Model of L2 Acquisition: Input Processing

The Computational Model implies that the human mind works like a computer. The learner is exposed to input, which is processed in two stages:

1. First, parts of it are attended to and taken into short-term memory. These are referred to as intake.
2. Second, some of the intake is stored in long-term memory as L2 knowledge.

The process responsible for creating intake and L2 knowledge occurs within the “black box” of the learner’s mind where the learner’s interlanguage is constructed. Finally, L2 knowledge is used by the learner to produce spoken and written output.