It has been suggested that people differ in the extent to which they possess a natural ability for learning an L2. This ability, known as language aptitude, is believed to be in part related to general intelligence but also to be in part distinct.

Early work by John Carroll led to the identification of a number of components of language aptitude. These are:

1. Phonemic coding ability, i.e. the ability to identify the sounds of a foreign language so that they can be remembered later.This ability is also seen as related to the ability to handle sound-symbol relationships (for example, to identify the sound which ‘th’ stands for).

2. Grammatical sensitivity, i.e. the ability to recognize the grammatical functions of words in sentences (for example, the subject and object of a sentence).

3. Inductive language learning ability, i.e. the ability to identify patterns of correspondence and relations between form and meaning (for example, to recognize that in English ‘to’ can denote direction and ‘at’ location).

4. Rote learning ability, i.e. the ability to form and remember associations between stimuli. This is believed to be important in vocabulary learning.

Research involving language aptitude has focused on whether and to what extent language aptitude is related to success in L2 learning. There is strong evidence that it is. Learners who score highly on language aptitude tests typically learn rapidly and achieve higher levels of L2 proficiency than learners who obtain low scores. Furthermore, research has shown that this is so whether the measure of L2 proficiency is some kind of formal language test or a measure of more communicative language use.

Most of the research on the relationship between language aptitude and L2 proficiency took place in the 1950s and 196Os and, therefore, predates the birth of SLA. From an SLA perspective the key question is: How does language aptitude relate to the processes of interlanguage development? One interesting possibility is that different components of language aptitude may be implicated in different stages of processing. Phonemic coding ability would seem relevant to the processing of input, grammatical sensitivity and inductive language learning ability to the central processing stages involving interlanguage construction, and memory to the storage and access of language. However, such a proposal, while interesting, remains speculative.

(Selected from Second Language Acquisition by Rod Ellis)