According to Hulstijn (2005), there is least consensus as to the differentiation between implicit and explicit learning. Language teachers always ask one question in that whether they should teach grammar in an explicit form and manner. Psycholinguists of second language (L2) acquisition very often raise an issue as to whether the adult can learn a language effectively through the same implicit learning mechanisms as the child uses in learning a first language (L1). Nonetheless, it is pivotal to understand the difference that lies between implicit and explicit learning mechanisms, and the role they play in L2 teaching & learning. Hence, the purpose of this paper is to examine the issues arising from implicit and explicit learning and how they relate to L2 teaching and learning.
There are some basic definitions, which are very useful in this paper in putting the thematic issues into perspectives that distinguish implicit and explicit learning.
Implicit and Explicit Learning
Implicit learning is input processing which takes place unconsciously and without conscious intention. Explicit learning is input processing with such intention to find out whether there are regularities in the input information. If positive, learners have to make use of these regularities to formulate related concepts and rules. Notably, definition of learning, be it implicit or explicit, is often in connection with the nature of the knowledge acquired. Implicit and explicit learning is then equivalent to the learning of implicit and explicit knowledge. Pedagogically, implicit L2 learning may be defined as learning without the aid of grammar rules while explicit L2 learning requires the aforesaid aid (Hulstijn, 2005).
Implicit and Explicit Knowledge
If a learner has no awareness of the regularities underlying the knowledge acquired, that knowledge is said to be implicit; whereas if a learner can verbalize the regularities underlying the knowledge learned, that knowledge is said to be explicit (Hulstijn, 2005).
Implicit knowledge is often connected with automatic processing while explicit knowledge requires enduring effort in the learning process. Both declarative and episodic knowledge are explicit knowledge. Knowledge is declarative when one can explicitly declare or verbalize the knowledge acquired. One knows 'when and where' of an episode and if one can have that episodic memory, one can be said to have acquired that episodic knowledge (Hulstijn, 2005). For example, L2 learners may have episodic knowledge of new and recently encountered L2 words or expressions acquired.
Implicit and Explicit Memory
Implicit memory is memory of a past event without conscious awareness; however, explicit memory involves in conscious awareness (Schacter, 1987). Regarding implicit memory tasks, there is no association with past events where participants are simply asked to perform the task as accurately and fast as possible. In contrast, participants are explicitly asked to recollect past events or to refer to previously studied events in performing explicit memory tasks.
THREE FACTORS THAT CAUSE CONFUSION
Hulstijn (2005) identifies three factors that cause confusion in the understanding of the definition of implicit and explicit learning.
Effects of Attention
For L2 learning to take place, learners should pay considerable attention and awareness as to elements of the surface structure of utterances. Schmidt (2001) suggests that attention should play an important role in implicit learning much more than in explicit learning.
Frequency of Knowledge Exposure
A machine language comprises a set of comprehensive form-meaning units and syntactic rules, corporated with well-formed in grammar and well-defined strings in semantics. However, the characteristics of natural languages are absent with form-meaning relationship, from morpheme to the text level. Regarding lexicon and grammar aspects, they consist of too many ambiguous form-meaning relations which disallow a thorough understanding of them via various kinds of linguistic rules. Nonetheless, it is reasonable to argue that learners can have either implicit or explicit knowledge gained in any given learning situation.
Individual Differences in Language Learning
Hulstijn (2005) agrees with the notion of the effects of individual differences in implicit and explicit language learning such as aptitude, intelligence and working memory, which can be related to the concepts of implicit and explicit learning and knowledge. He opines that majority of the SLA literature has studied individual differences in language learning more than the fundamental issue of language learnability in question.
DIFFERENTIATING IMPLICIT AND EXPLICIT KNOWLEDGE
Ellis (2004) highlights seven ways concerning implicit and explicit knowledge of language, which can help differentiate between the two types of knowledge to serve the purpose of a better understanding of their constructs.
Ellis (2004) differentiates epilinguistic data from metalinguistic data for the examination of child language development. When a child exhibits epilinguistic behavior, he / she can be said to have demonstrated instinctively awareness of implicit grammatical rules. He comments that epilinguistic behavior is obvious when the child can immediately identify those ungrammatical errors in a sentence. In addition, when the child expresses conscious awareness of reasons behind an ungrammatical sentence and can show understanding of such ungrammaticality with an explanation, he / she can be said to have exhibited a metalinguistic behavior. It follows that over time, implicit knowledge of the children grows increasingly which allows room for explicit representation in the development. L2 acquisition is a similar process. If the L2 learners are taught explicit rules that can integrate into 'emerging representational structure', such L2 teaching can be said to be effective.
Type of Knowledge
In his study, Anderson (1983) distinguishes between procedural and declarative knowledge by commenting that reorganization of knowledge is slow in changing from one form of representation to another. Procedural knowledge is intuitive to a great extent. Declarative knowledge is explicit and all inclusive in nature. Declarative knowledge of language includes knowledge of abstract rules (e.g., the use of articles), fragments and exemplars (Ellis, 2004). When the learner empowers himself / herself with the control over the fragments and exemplars, and also the reorganization of declarative knowledge of rules into increasingly meticulous if-then productions, procedural knowledge then results.
Systematicity and Certainty of L2 knowledge
Reber, Walkenfeld, and Hernstadt (1991) argue that implicit knowledge is less diverse than explicit knowledge. Researchers suggest that interlanguages of learners (i.e., their implicit knowledge) are greatly systematic which contain different categories of rules. In contrast, explicit knowledge is often inexact, ambiguous, and irregular. Learners very often have difficulties in understanding as to how rules specifically work. Therefore, implicit knowledge is deemed to be more organized than explicit knowledge even though both types of knowledge involve certain degree of nonsystematicity and uncertainty.
Accessibility of Knowledge
Implicit knowledge contains intuitive processing while explicit knowledge implies controlled learning processing. On the one hand, learners structure messages by their implicit knowledge when communicating; on the other hand, if language form is required, they have to rely on explicit knowledge and its accessibility to monitor for accuracy's sake.
Ellis (2004) comments that it is obviously possible for learners to access to explicit knowledge, suggesting that explicit knowledge can be fully mechanized and therefore, it becomes practically same as implicit knowledge. However, Hulstijn (2002) opines that the aforesaid stays a basic difference between mechanized explicit knowledge and implicit knowledge regarding their accessibility.
Use of L2 Knowledge
Bialystok (1982) remarks that the use of implicit and explicit knowledge depends on the specific tasks learners are asked to perform. From the perspective of sociocultural theory, Ellis (2004) points out that explicit knowledge can help learners to gain control in challenging situations. Learners typically use declarative information to help them to address an issue such as when being asked to perform a think-aloud task (e.g., at the time of completing a grammaticality judgment test).
Explicit knowledge can be verbalized regardless of the learners' level of competence in verbalizing it. The skill of learners in verbalization may partly rely on their knowledge of metalanguage. As far as implicit knowledge is concerned, it may not be verbalized. Thus, without any prior formulation of explicit representation, any attempt to verbalize it will not be feasible. According to Ellis (2004), it may be possible to form explicitness or implicitness of a statement as to how its linguistic feature is expressed. For example, it is more explicit to say 'I know that is a relative pronoun that can refer to both animate and inanimate nouns' rather than saying 'that is a relative pronoun' or 'I used the word that'.
Many SLA researchers including Ellis (2004) argue that explicit knowledge is learnable at all ages, while implicit knowledge is not. For instance, learners with first languages (L1) which lack ability to solve grammatical functions may experience difficulties in acquisition. It is because for L1 learners, whose implicit knowledge had passed a certain sensitive age, may continue to develop explicit knowledge. Learnability of explicit knowledge is also controversial. Krashen (1982) questions that most learners are able to learn only formal, functional and simple rules, but Ellis (2004) shows that German learners of English who attain the university level can develop greatly sophisticated explicit knowledge.
COMPARING IMPLICIT AND EXPLICIT LANGUAGE LEARNING
Concepts such as consciousness, awareness, attention, noticing, and focus in L2 learning demonstrate a positive role through the explicit teaching of grammar, explicit error correction and input enhancement (Dekeyser, 2005).
Not many laboratory studies are used to compare implicit and explicit learning of new L2 material. On the one hand, it may involve volunteer learners who have never contacted a language before. On the other hand, others may be assigned a special experimental task which they have not been exposed before. One experiment shows the benefit of explicit rule presentation over word / pronunciation pairings while a second experiment demonstrates that explicit presentation of the rules are useful only if they are followed by practice (Dekeyser, 2005).
Even lesser studies have compared implicit and explicit tasks in a real classroom setting. Similar experiments were conducted by Scott (1990) with college students of French as a foreign language. In the studies, in the absence of any practice, an explicit group was presented with rules about relative pronouns and the subjunctive, while an implicit group read a text with a 'sea' of relevant forms. Both studies showed a better performance for the explicit group on written post-tests; and another study did not result in any obvious differences. Both treatment conditions in the studies appeared not very realistic, as the explicit condition subjects never practiced, and the task was not long enough for implicit learning to become effective.
TEACHING AND LEARNING OF L2
A decent amount of comparisons were made between implicit and explicit learning in specific structures which give an idea that learning explicitly is better than implicitly. However, few empirical studies on L2 acquisition have directly tackled the problem of differential effectiveness of implicit and explicit learning in relation to the learning of the nature of the grammar element. Krashen (1994) argues that implicit learning is especially beneficial to complex structures. Most people are difficult to grasp explicitly for such complex structures and can be impossible especially without instruction. Surprisingly, implicit learning will show a relative advantage for such structures. Most people feel difficult to grasp explicitly for such complex structures and may be impossible especially without instruction. A study shows that, on the one hand, out of the four conditions for hard rules, implicit induction was second best and explicit induction the worst, respectively; but on the other hand, the implicit condition was the worst for easy rules (Dekeyser, 2005).
Corrective Feedback of Implicit and Explicit Learning
Ellis (2006) sheds lights to the teaching and learning of L2 grammar either explicitly or implicitly. A review of previous studies of the effects of implicit and explicit corrective feedback on SLA reveals a number of methodological problems such as valid measures of implicit knowledge. The study designed by Ellis (2006) was to provide a precise comparison between implicit and explicit corrective feedback regarding the acquisition of past tense -ed. The aforesaid concepts could be operationalized in terms of partial recasts of speakers' errors and explanations of the learners' error metalinguistically.
The effects of the corrective feedback on learning were assessed by means of tests designed to measure learning of both implicit and explicit L2 knowledge. The tests were conducted before the instruction, one day after the instruction, and again two weeks later. The study shows that explicit feedback is more effective than implicit feedback in promoting system learning as well as item learning. In addition, it seems that explicit feedback is more likely to contribute to the cognitive comparison that supports learning within the classroom context.
Age and context differences
It is hypothesized that adults and children apply very different mechanisms for L2 learning. This idea can be found from Robert Bley-Vroman's (1988) Fundamental Difference Hypothesis. Explaining various observed differences in strategy and success between adults and children, Bley-Vroman (1988) suggests that children are more advantageous in using Universal Grammar and domain-specific learning procedures, while adults tap on native language knowledge and general problem-solving skills and systems. Bley-Vroman's distinction by and large matches with this dichotomy, even though he does not use implicit and explicit directly. Whilst the use of Universal Grammar and language-specific learning mechanisms by children occurs outside their awareness, adults make use of their analytical competence to contemplate about L2 structure and its differences with L1.
From childhood to adulthood, the shifting from implicit to explicit learning processes accounts for the two major findings in relation to age differences in L2 learning - children can learn better and adults can learn faster (Marinova-Todd, Marshall, & Snow, 2000). Consequently, given enough time in an unorganized environment, children turn out to be better than adults in learning. However, for instance, in a context of traditional school, with limited time and greatly organized learning, adults and older children can learn more under the same amount of time.
Fairly to say, first, that the amount of L2 research is narrowly focused on the implicit-explicit differentiation is in itself quite constrained, both in terms of number of studies, duration and scope of the learning target. Second, most of the research studies have been conducted in laboratory where its ecological validity is much limited when compared to classroom situations. Third, there are no longitudinal studies in tracing the role of implicit and explicit learning in untaught L2 acquisition. Fourth, the criterion measures always limit themselves to grammaticality judgments or fill-in-the-blank tests instead of adopting freely constructed discourse. Finally, it is difficult for psycholinguists and language teachers to meet the methodological requirements for ensuring pure implicit / explicit learning or for using a pure measure of implicit / explicit knowledge.
Researchers coming from different disciplines, believing in different schools of thought or using distinct terminology are questioning that L1 acquisition or its grammar depends mainly on implicit learning process while L2 acquisition depends very much on both implicit and explicit learning. In the field of L2 acquisition, how then can we make progress towards a better understanding of fundamental importance both to theories of L2 acquisition and to L2 pedagogy?
Effects of attention, frequency of knowledge exposure and individual differences in language learning are the three factors that may cause confusion in interpreting the definition of implicit and explicit learning.
In differentiating implicit and explicit knowledge, Ellis (2004) mentions seven ways for understanding of them in detail. They are: awareness, type of knowledge, systematicity and certainty of L2 knowledge, accessibility of knowledge, use of L2 knowledge, verbalization and learnability. Consciousness, awareness, attention, noticing and focus definitely play an important role in the explicit teaching of grammar, explicit error correction and input enhancement where implicit and explicit learning of new L2 material can be compared.
Research findings in relation to age differences in L2 learning suggest that children can learn better and adults can learn faster. More studies are expected to be conducted in the classroom context to explore ways to improve the understanding of implicit and explicit learning, knowledge and pedagogy.