Introduction

People marvel at the ease and rapidity with which children acquire their first language. It is generally observed that by the age of five every normal child obtains a full knowledge of the grammar of the language of the community in which they live. This amazing feat is often contrasted with the hopeless failure encountered by adults acquiring a second language (L2):

The outcome of first language acquisition is success: normal children acquire the grammar of the ambient language. Adult second language acquisition, on the other hand, results in varying degrees of success. Failure to acquire the target language is typical. (Birdsong, 1992: 706)

It is true that many adults learn to communicate effectively using an L2, and some few appear to have extensive if not perfect knowledge of the grammar of the L2. Nevertheless, the overwhelming majority are not able to achieve anything like the same level of mastery as that achieved by every normal child. (Schachter, 1996a: 160)

It is much more difficult to learn a second language in adulthood than a first language in childhood. Most adults never master a foreign language, especially the phonology – hence the ubiquitous foreign accent. Their development often 'fossilizes' into permanent error patterns that no teaching or correction can undo. (Schwartz, 1997)

It has been widely observed that children from immigrant families eventually speak the language of their new community with native-like fluency, but their parents rarely achieve such high levels of mastery of the spoken language ... Many adult second language learners become capable of communicating very successfully in the language but, for most, differences of accent, word choice, or grammatical features distinguish them from native speakers and from second language speakers who began learning the language while they were very young. (Lightbown & Spada, 1999: 60)

The difference in outcome between the child first language (L1) and adult L2 cases, as Schachter (1996a) puts it, is strong and unambiguous.

As early as 1972, Selinker conjectured that the absolute success in a second language affects a mere 5% of learners. Similarly, Eubank and Gregg (1999: 77) claim that 'with few exceptions adult learners fail, often miserably, to become indistinguishable from members of the ambient L2 speech community'.

If the 5% success rate in L2 acquisition is compared to the success rate in L1 development, the figures appear to be reversed, since in the latter case it is the failure rate that seems to stand at a mere 5%, and this is accounted for exclusively by those with specific language impairments (Eubank, 1997, SLART-L on-line communication; see also Bley-Vroman, 1989; Selinker, 1972; Selinker & Lamendella, 1978).

The overwhelming success surrounding first language acquisition (FLA) begs an important question: How is acquisition possible? This question was originally formulated as a logical problem in language acquisition (Hornstein & Lightfoot, 1981) to address the fact that learners' linguistic knowledge or competence transcends the input to which they have been exposed. Child first language acquirers have been noted to be capable of developing a robust and highly generative grammar despite exposure to input that is degenerate, under-determinate and finite. The general explanation given for the logical problem has been that child first language acquisition is driven by an innate language-specific mechanism known as Universal Grammar (UG). As Chomsky (1965: 58) states:

A consideration of the character of the grammar that is acquired, the degenerate quality and narrowly limited extent of the available data, the striking uniformity of the resulting grammars, and their independence of intelligence, motivation and emotional state, over wide ranges of variation, leave little hope that much of the structure of language can be learned by an organism initially uninformed as to its general character.

Some researchers (e.g., Gregg, 1996; L. White, 1989) maintain that the same logical problem also obtains in second language acquisition (SLA). That is, in SLA there exists a similar gap between input on the one hand and the acquired competence on the other (L. White, 1996). Gregg (1996) argues that insofar as second language grammar (i.e., interlanguage) – however imperfect – is underdetermined by input data, the logical problem obtains.

Other researchers (e.g., Bley-Vroman, 1989; Schachter, 1988, 1996a), however, challenge the straightforward application of the logical problem to SLA, pointing out that SLA is characterized more by failure than by success:

Few adults are completely successful; many fail miserably, and many achieve very high level of proficiency, given enough time, input, effort and given the right attitude, motivation and learning environment. (Bley-Vroman, 1989: 49)

By presenting a different view on the ultimate attainment of SLA, these researchers suggest an alternative version of the logical problem, namely, why is complete acquisition impossible? The explanation sought subsequently is that unlike first language acquirers whose acquisition is guided by UG, adult second language acquirers rely on their general problem-solving capacity for L2 development.

In postulating his Fundamental Difference Hypothesis, Bley-Vroman (1989) underscores nine major characteristics of second language acquisition: (1) lack of success; (2) general failure; (3) variation in success, course and strategy; (4) variation in goals; (5) fossilization; (6) indeterminate intuitions; (7) the importance of instruction; (8) the need for negative evidence; and (9) the role of affective factors. These features set SLA distinctively apart from FLA. In a similar vein, Schachter (1996a: 160–161; see also Schachter, 1988) points out four major dimensions along which SLA differs from FLA: (1) ultimate attainment (i.e., 'the ultimate attainment of most, if not all, of adult L2 learners is a state of incompleteness with regard to the grammar of the L2'); (2) fossilized variation (i.e., 'long after cessation of change in the development of their L2 grammar, adults will variably produce errors and non-errors in the same linguistic environments'); (3) lack of equipotentiality (i.e., 'the adult's knowledge of a prior language either facilitates or inhibits acquisition of the L2, depending on the underlying similarities or dissimilarities of the languages in question'); and (4) the role of prior knowledge (i.e., 'the adult learner's prior knowledge of one language has a strong effect, detectable in the adult's production of the L2').

The debate on the logical problem of SLA continues. Nonetheless, it becomes increasingly clear that unlike in FLA, a monolingual context, where success dominates, in SLA, a multilingual interactive context, success and failure co-exist, with both warranting explication. The logical problem in...