Due to the insights of second language acquisition, the need of recycling for second or foreign language learning has also been stressed in materials development as well as course syllabus design.
Tomlinson (1998) has indicated that “materials should take into account that the positive effects of instruction are usually delayed” (p.15). Since acquisition is a gradual and dynamic process rather than an instantaneous one, learners cannot be expected to learn a new feature and be able to use it in a lesson. Therefore, it is
important for materials to recycle instruction and to provide frequent and ample exposure to the instructed language features in communicative use (Tomlinson, 2003). Tomlinson (1998) suggested one way to promote durable learning. He stated:
The conventional textbook approach of PPP (Presentation- Practice-Production) could be used to promote durable learning if the objective of the Production phase was seen as reinforcement rather than correct production and if this was followed in subsequent units by more exposure and more representation relating to the same feature. (p.16)
Therefore, if the structures targeted in the lesson are recycled in the subsequent lessons, students’ retention and recall of the structures will be enhanced and strengthened. Howatt (1974) also noted the need of recycling in the teaching materials. He pointed out the need of revision in the language course. As he mentioned:
Revision should be both cumulative and recurrent. When a learning point has been introduced into the materials, it should be used again and again in the succeeding units. Of course, some points are more important than others and it would be physically impossible to bring back every single item in every unit, so choices have to be made.
However, if the notion of cumulative recurrence were to be applied to teaching materials in even the most limited way, the effect would be startling. (p.19)
According to Howatt (1974), repeated experience of same features of language should always be in context and preferably in different contexts so that students might not get bored and could always be reminded of what they have learned.
In course syllabus design, one is faced with a choice between two approaches to the sequencing of items in the course, namely a linear, and a cyclical or spiral
gradation (Dubin& Olshtain, 1986; Richards, 2001; Stern, 1992). The linear approach would be to teach grammatical structures from start to finish through a syllabus covering each item thoroughly before the next items appear, while the cyclical or spiral approach would be to reintroduce and recycle structures occasionally with each time at a more complex or difficult level. Researchers have recommended a cyclical or spiral treatment of grammatical structures rather than a linear one due to the reason that the cyclical approach allows for the kind of gradual acquisition that is compatible with what is known about interlanguage development (Bai, 2001; Foppoli, n. d.; Howatt, 1974; Larsen-Freeman, 1991; Martin, 1978).
With a spiral approach, a lot of recycling will be required. That is, a new item will not be introduced once and then dropped; instead, it will be revisited in different manifestations at various times in the course so that learners might become aware of its relevance and might gradually grow into the language as their experience of it increases.
Studies on vocabulary acquisition have also shown the need of recycling in language learning (Horst, Cobb, & Meara, 1998; Kanchroo, 1962; Liu, 2002; Nation, 1990; Salling, 1959; Saragi, Nation, & Meister, 1978; Schmitt & Schmitt, 1995).
They indicated that multiple exposures to a word could benefit acquisition and suggested that the exposures ranging between five to sixteen times to a word could better ensure vocabulary acquisition. For example, Salling (1959) reported that at least five times of exposures were required in order to acquire a word. Kanchroo (1962) suggested that words encountered seven or more times in a textbook could facilitate vocabulary acquisition. Saragi, Nation, and Meister (1978) found that words appeared fewer than six times were learned by half of the participants, whereas words presented six times or more were learned by 93% of them,
Meara (1998), students were required to read a book over a 10-day time frame.
Results indicated that words repeated eight times or more had a higher pick-up rate.
Focusing on Taiwanese senior high school learners, six encounters were found to be beneficial for vocabulary acquisition although an increase from six to twelve encounters was not proved to be significant (Liu, 2002). Gu (2003) later summarized that the number of exposures needed for the mastery of a word actually involved many other factors, such as the salience of the word in context, the richness of contextual clues, or the learner’s existing repertoire of vocabulary. Although there is no definite answer to the number of exposures needed for vocabulary acquisition to take place, the need of multiple exposures to a word can never be overemphasized.
Although no research has been done to examine the number of exposures needed for the acquisition of a particular structure, it is without doubt that recycling is a necessary part for the learning of grammar. Just as Doughty and Williams (1998) has suggested, “although a single encounter with a form may lead to an acquisition breakthrough, we do not know whether it is the tenth, fifth, or thousandth encounter that will be the crucial one” (p. 253). Until we know more, it can be assumed that multiple encounters are required for engaging learning process, such as testing, comparison, or restructuring. As a consequence, in order to facilitate second or foreign language acquisition, recycling various aspects of the target structures over a period of time for learners is undoubtedly essential.