Listening Activities for Effective Top-down Processing
Ji Lingzhu

Introduction
Once I played the recording of a hundred word passage on how to advertise for a kind of very expensive perfume to my students in the listening class. Before they listened, all the necessary new words like tuxedo, Leonardo da Vinci etc, were given and explained carefully. The tape was played three times before I asked them to retell the main idea of the passage. Half of them failed to give the correct answer. Even some of the strong learners failed. My students told me they did not know what the writer was talking about, although they knew all the words and the grammatical rules. Suddenly one lady student who seldom opened her mouth in the listening class stood up, telling me that the writer was talking about how to make an advertisement for a kind of perfume. She further explained that she was interested in reading fashion magazines in her spare time, and people always tried many ways to advertise their products. That was really out of my expectation because she was not very strong in listening comprehension.
The text itself was not very difficult linguistically and the students were capable of understanding it.  What caused the comprehension failure?
Just like reading, in listening, there are also two simultaneous and complementary ways of processing a text. In top-down processing, learners use their prior knowledge to make predictions about the text. In bottom-up processing, learners rely on their linguistic knowledge to recognize linguistic elements -- vowels, consonants, words, sentences to do the construction of meaning. Teachers often think that the learners hear every sound, word or sentences before they understand the general meaning of the passage. However, in practice, they often adopt a top-down approach to predict the probable theme and then move to the bottom-up approach to check their understanding.rAccording to the schema theory, the process of comprehension is guided by the idea that input is overlaid by the pre-existing knowledge in an attempt to find a match. The readers must relate textual materials to their background knowledge, so that the new input from a reading passage is mapped against some prior schema. All aspects of the previously existing schema must be compatible with the new input from the text. In a commercial society like ours, my students do not lack the schema for advertising.  However the passage is not about the advertisement for the perfume, but about his thoughts on the ways to advertise. The students reported that they did not think about the advertisement planning process while they listened to the passage. The lady student who did well reported that she had read an article on how to advertise for a famous brand of shirt. Most of the students actually failed because they were not very familiar with the topic.
In English listening, the content schema must be activated in order for the learners to access their prior knowledge. Consequently it is our job to use some classroom activities to help them. First of all, we must assess the students` level of background knowledge on a particular topic before the students listen to the text. If the students lack specific content schema, we should provide a remedial lesson on the topic to bring their level of content schema up to the level where they can better comprehend the text. Or we revise the teaching materials so that they will not be too demanding for the students. Furthermore, the teachers can use the information gained at this time to make specific lesson plans for the remainder of the listening lesson on that particular topic.
Activities to Activate Students` Prior Knowledge
To effectively activate the students` prior knowledge, I often use activities in my listening class and will introduce some of them here in this article.
Word Association Tasks
This method helps to determine what prior knowledge students bring to the new topic before they listen to the passage. They will respond to a key word or phrase such as "Crimes are harmful to the society." They can write down as many words and phrases as possible in five minutes` time related to this topic, or they may write freely on this topic. While they write, they should not worry about the words and sentences they write, just pay attention to the content. The whole process takes about ten minutes. The teacher can write down the main ideas on the board. Then according to the information, the teacher should adjust his/her teaching plan. The free association method of assessing background knowledge was originally developed as part of a pre-reading plan. Later it was further developed as a measure of prior knowledge. The learners are usually given three content words or phrases related to a topic and asked to write anything that comes to mind when they hear each word or phrase. We can also use the semantic webbing method. In this approach, teachers graphically connect the various concepts and key words surrounding a particular topic on the blackboard, helping students to see the possible relationship between ideas discussed. Here we are not creating new knowledge, but making students aware of the knowledge they already have by giving structure to the content information. This process will enable them to connect what they are going to learn with what they have already know.
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