What predicts success in second language acquisition? Or: babies know statistics!

Apparently, there are significant individual differences in the  people's ability to learn a second language.  What causes them?  And what predicts fast and successful acquisition of a second language?

There are two approaches that try to explain these individual differences.  Probably the best explanation combines both approaches.

The first approach argues that the acquisition of a second language is dependent on the same linguistic abilities that allowed for the first language acquisition.  This approach is supported by studies showing that phonological awareness, syntactic knowledge, orthographic knowledge and vocabulary in the first language usually predict success in second language acquisition.  When a child immigrates with high cognitive academic language proficiency in this first language (a level which is usually achieved through reading), he usually acquires high cognitive academic proficiency in the second language  faster and better than a child immigrating with only basic communication skills in his first language.  According to this view, linguistic measures are the best predictors of success in second language acquisition.

The second approach argues that second language acquisition is like any other learning process.  In any learning process we identify and perceive systematic and probabilistic structures in our environment.  Acquiring  second ( and first) language is mainly a process of acquiring and assimilating the statistical features of our linguistic environment.

What does this mean?

Statistical learning refers to the cognitive process by which repeated patterns, or regularities, are extracted from the sensory environment. Such learning often happens without an intention to learn and without an awareness of what was learned.

How do babies acquire language, and how do they identify words in the stream of voice sounds they hear when someone talks to them?  Saffran and colleagues showed that 8-month old 2 infants are sensitive to auditory statistical regularities. They exposed infants to a stream of syllables, constructed from 12 syllables (e.g., tu, pi, ro, bi, da, ku, go, la, bu, pa, do, ti) that formed four tri-syllabic “words” (e.g., tupiro, bidaku, golabu, padoti). After a 2- minute exposure to streams such as “bidakupadotibidakugolabutupiro …”, infants were tested in a habituation procedure with two tri-syllables. One was a “word” (e.g., “bidaku”) heard during the 2 min-exposure phase, and the other was a foil (e.g., “tudabu”). The foils were composed of three syllables that were never paired together. Saffran and colleagues found that infants showed more interest in the foil than in the word, as indexed by increased listening time (e (i.e., the duration of showing interest in each tri-syllable). That is, infants are capable of statistical learning after just two minutes of exposure to sound sequences.

Oral  and written words in any language are built by rules that restrict and determine their internal structure (for example, the sound sequence "shchtz" is not possible in English, and "lpstzr" cannot be an English word).  Each language has its own statistical structure, and when people acquire a second language, they implicitly acquire, according to the second approach, a new set of statistical rules.

Thus, according to the second approach, the fundamental cognitive faculty of implicit correlation-learning which underlies any form of learning plays a primary role in second language acquisition.

The degree of similarity between the statistical characteristics of the first and second languages can affect the process of statistical learning of the second language structure.  Like any other cognitive ability, individual differences in sensitivity to correlations in the environment can affect second language acquisition.

Is it really so?  And how do we measure it?  In the next post.