Past puberty our capacity to learn foreign languages decreases, but adults do not learn a second or additional language at the same pace. Many individual variations affect the outcomes, continue reading to find out which one seems to be the most influential one.
Besides age, aptitude seems to be the best language learning predictor in L2/3/4 adult learners. The construct of foreign language aptitude is strongly associated with the name of John B. Carroll, the first to establish the methodology for studying aptitude, and its nature. Carroll (1962) believed foreign language aptitude to be a specific autonomous talent or a group of talents separated from intelligence. Far from regarding aptitude as a monolithic construct, Carroll, pinpointed four independent subcomponents able to help foreign language learning: 1) Phonemic coding ability, the ability to distinguish foreign sounds and to encode them so that they can be recalled; 2) Grammatical sensitivity, the capacity to recognise the functions of words in sentences (a skill strictly related to the ability to assess whether or not words in different sentences perform the same function); 3) Inductive language learning ability, the capacity to deduce and extrapolate rules about a language from language samples; 4) Associative memory, the capacity to form associations in memory. He also suggested that aptitude has to be considered as a fairly stable construct and maintained a neutral position as to whether aptitude exists within an individual from birth or is the result of early experience. As a result of his work, Carroll published the Modern Language Aptitude Test (MLAT) (Carroll and Sapon 1959), a measure which generated significant high correlations with language performance. Up to these days, this test is still the keystone of aptitude research. The total score produced by the MLAT is at the base for predictions of language learning success. However, despite its importance, the study of foreign language aptitude decreased considerably by the 1970s: first of all, because it was perceived to be anti-egalitarian; second, because it was seen as irrelevant and associated to old-fashioned class learning; third, because at that time English language teachers did not appear to be interested in the differences present between learners. However, the research scenario changed from 1990s with research focusing on investigating individual differences affecting language learning success in L2 learners. The MLAT test was then, reconsidered to be a respected test for foreign language aptitude prediction. There was also a continuation in believing that aptitude could significantly be influenced by affective variables. In addition, aptitude was then reconsidered to be a cognitive construct influenced to a great extent by language variables especially by the individual’s skills related to his/her phonological and orthographic native language systems. The latter concept was at the basis of the Linguistic Coding Differences Hypothesis formulated by Sparks and Ganschow (1991). In recent literature, aptitude is thought to be one of the key factors which influence adult second and additional language learning. Recent studies have suggested that aptitude correlates significantly positively, especially in native-like adult L2 learners, producing positive effects, which may compensate for the negative effects linked to the brain maturational constraints and the critical period. However, high or low aptitude seems to be irrelevant or of a minor importance in early acquisition. Abrahamsson and Hyltenstam (2008), investigated L2 proficiency and language aptitude in 42 near native L2 speakers of Swedish perceived to be native speakers by mother-tongue speakers of Swedish. Their study was conducted in order to test DeKeyser’s (2000) hypothesis according to which aptitude is a strong predictor of language achievement in naturalistic acquisition as well as in an instructed context. Indeed, the results indicated that high levels of analytical abilities are required in learners who can pass as native speakers in daily communication. However, it was also suggested that even a high degree of aptitude does not represent a sufficient condition for achieving a “complete” native-like fluency.