As you plan your lesson, do you start with the small building blocks and then expanding? Or do you start with the big picture and break it down? These two approaches actually have names - "bottom-up" and "top-down" approaches. The terms have been borrowed from cognitive psychology, but derive originally from computer science, where they distinguish processes that are data-driven from those that are knowledge-driven.
Imagine two situations: listening to a friend telling a story about last weekend and reading a recipe where you read the ingredients first. How do you listen or read in each case? Are there any differences? In the situation with a friend, you understand the general idea first, in contrast, when reading a recipe understanding the exact words is likely to be more important. The way you listened to the story could be characterised as "top-down" approach. The second comprehension is achieved by dividing and decoding the parts - "bottom-up".
"Bottom-up" processing
Vandergrift states that listeners or readers use BUP “when they use linguistic knowledge to understand the meaning of a message. They build meaning from lower level sounds to words to grammatical relationships to lexical meaning in order to arrive at the final message”.
Bottom up teaching starts with small details, like vocabulary words or grammar structures. As students have learnt them, the teacher broadens the scope of the lesson to include a reading or listening passage.
Bottom-up reading strategies begin with letter-sound correspondences (the bottom) to achieve comprehension (the top), starting with letters and sounds, building to morpheme and word recognition, and then gradually moving to grammatical structure identification, sentences, and longer texts. A phonics approach to teaching reading supports bottom-up processes.
"Top-down" processing
Top-down Processing (TDP), in contrast with BUP, is holistic, “going from whole to part, and focused on interpretation of meaning rather than recognition of sounds, words and sentences. Listeners actively formulate hypotheses as to speaker's meaning, and confirm or modify them where necessary”.
Top-down strategies instruction focuses on activities that construct meaning, which students generate by employing background knowledge, making predictions, and searching the text to confirm or reject the predictions that are made. Other examples of common top-down listening / reading activities include putting a series of pictures or sequence of events in order, listening / reading to conversations and identifying where they take place, reading information about a topic then listening to find whether or not the same points are mentioned, or inferring the relationships between the people involved.
During top-down processing of a word, students use their lexical knowledge to identify the incoming word as they connect the word to their knowledge of other related words and concepts. Students learn to recognise the words rather than read them letter by letter or syllabus by syllabus.
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