Wednesday, November 08, 2006

Up from the Bottom or Down from the Top?

By Peter McKenzie-Brown

Psychology long ago began to debate two views – “top-down interpretation” and “bottom-up processing”– of how we understand language. Although the evidence is ambiguous, researchers generally believe they are distinct but complementary processes. For language instructors, the debate is less important than an appreciation of the roles these parallel processes play in classroom teaching and learning.

This discussion argues that good teaching practice accepts both views of language learning. However, their relative importance largely depends on the skills of the language learner.

To appreciate this, let’s begin with points of view. The advocates of “top-down interpretation” argue that background knowledge and previous experience of a situation, context, and topic play primary roles in helping us interpret meaning. We use prior knowledge and experience to anticipate, predict, and infer meaning. By contrast, the advocates of “bottom-up processing” believe language relies more heavily on decoding the sounds and letters of a language into words, clauses, sentences, and such. We then use our knowledge of grammatical, syntactic and lexical rules to interpret meaning. In this view, language users work from the bottom – the sounds they hear and the letters they encounter – to identify meaning.

To put that broad debate into context, consider that the primary focus of communicative language teaching is to develop communicative competence. CL teachers develop this competence through the use of materials and activities that focus on using language functions – for example, describing people and telling time. Because native-speakers use higher mental schema when they are processing language, language teachers develop activities that will enable their second-language learners to do the same. Broadly speaking, activities of these kinds involve top-down learning skills.

Is this always a good thing? No. Some language teachers are too quick to jump on the top-down bandwagon. In our view, better teachers are those who strike a conscious balance between top-down and bottom-up learning, which both have roles in language instruction.

According to Robert Norris, who uses listening activities to illustrate, “If we…require (our) students to use native speaker processing skills without first giving (them) a firm grounding in decoding the stream of sounds they hear, we run the risk of causing (them) more frustration and confusion than they can handle.”

We will return to Norris’s thoughtful discussion shortly. In the meantime, remember that bottom-up processing is particularly important when learners use the receptive language skills of listening and reading, because it plays a big role in making input comprehensible. And comprehensible input is the engine of effective language acquisition.

Bottom-up…: The bottom-up view assumes that listening is a process of decoding sounds and graphemes (the letters of the alphabet). We start with the smallest units, and gradually decode them until we understand the content of what we are listening to or reading.

The number of micro-skills involved is large. For example, when we listen we discriminate among the distinctive sounds of English, recognize stress patterns and the rhythmic structure of English, and discern how we use stress and intonation to signal information. Also, we need to identify words in stressed and unstressed positions and in reduced forms. We also have to recognize grammatical structures and typical word-order patterns. Meaning and comprehension are the last steps in the decoding process.

When we read, we use the building blocks of language to make meaning of what we see on the printed page. Bottom-up processes include sounds and graphemes -- the representation of sounds by letters. In English this involves word recognition for the countless irregular spellings and a sophisticated system of punctuation. We then need to to process written information through grammar and sentences. From these blocks we build comprehension.

…and Top-down: By contrast, top-down proponents believe that language processing involves the reconstruction of meaning through prior knowledge or “schema.”

Listeners actively reconstruct the original meaning of the speaker using incoming sounds and other signals like body language as clues. Prior knowledge of context and situation enables us to make sense of what we hear. A native speaker, for example, may completely zone out while hearing the news, then snatch a few brief cues that quickly draw him in. Similarly, when we begin a phone conversation to make an appointment, we shift into formal speech-patterns for such situations. This is another instance of schema guiding language use.

We also use schema to help us understand what we are reading. For example, the format of letters, emails and magazine ads are similar from culture to culture. Their format, whether in the reader’s first or second language, provides specific and useful information about what we can be likely to expect. Other top-down skills include surveying, skimming, scanning, reading for full comprehension, reading between the lines (inference), and reacting personally to reading texts. Teaching these learning strategies to your intermediate students can greatly improve their reading comprehension.

The Language Level Issue: In his excellent discussion of top-down and bottom-up teaching, Norris argues that the teaching community’s eagerness to focus on top-down teaching is sometimes misguided. “Many of the listening materials on the market today are concerned chiefly with helping learners become more adept at improving top-down skills by having them (identify relevant information while ignoring unnecessary details.)”

He adds, “In order to simulate the knowledge that native speakers bring to listening, learners are often provided with vocabulary lists prior to the task and told who the speakers are, what the situation is, and what the topic is about. However, scant attention is paid to the phonological characteristics that mark informal speech. This seems a bit like putting the cart before the horse.”

Norris makes a strong case that teachers must develop both bottom-up and top-down skills, especially at the lower levels. “Teachers are asking a lot from their students… when top-down listening tasks are given without first assessing the students' ability to do bottom-up processing.” His argument is sound. Learners need many micro-skills learners for bottom-up processing, and a good teacher neglects them at his peril. This applies especially to beginning and early intermediate students.

Wrap-up: The main conclusion of this discussion is that we need to feed both learning processes when we are teaching our students.

How and when can we use top-down processing? When you are teaching, make sure your students are aware of the format and general content of a reading, for example. Tell them they are going to read a ghost story, for example, and then elicit ideas about what the content might be, what vocabulary might occur, and so on. This switches on the ghost-story schema in their brains, and also begins activating their English skills. You can do the same with listening. Tell them you are about to listen to a sports broadcast on the Football World Cup. Elicit information about football and the vocabulary they might expect to hear, and so on. Also, of course, a CL teacher is constantly using authentic activities to teach. Thus, a role-play “in the restaurant” is by its very nature a top-down comprehension activity.

In these and many other ways, you can take advantage of your students’ ability to use top-down comprehension to get them ready for the upcoming learning activity. As your students advance, you can use more sophisticated top-down schema and strategies.

Bottom-up skills are different. As we have suggested throughout, they are usually more basic and therefore more important for lower-level students. With those students, you need to spend time helping them recognize reduced speech, for example, and irregular spellings. In the early stages of language acquisition, automaticity in word recognition is critical.

Communicative language teaching emulates real-life language acquisition, which means our work has a top-down bias. Your class needs to use authentic activities and materials to function effectively, and those materials tend to be top-down. However, focusing exclusively on top-down teaching creates problems. Especially with beginning students, spend time developing bottom-up skills.
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