TOP-DOWN PROCESSING

The influence of higher-level (conceptual) knowledge upon lower level (perceptual) processing. The terms ‘top-down’ and ‘bottom-up’ are derived from computer science, where they refer respectively to information that is knowledge-driven and information that is data driven.

‘Top-down’ is sometimes loosely used as a synonym of ‘contextual’. However, strictly speaking, it refers not to a single level of processing buttoadirection of processing. Suppose the knowledge that a given word exists can be shown to affect the way we hear the sounds in that word. This can be described as a top-down effect, because knowledge at word level is influencing processing at a lower (phoneme) level. Similarly, the way in which speech or writing is planned can be described as a ‘top-down’ process since it begins with large, conceptual units (propositions) and ends with small, perceptual ones (words in the speaker’s mouth or on the writer’s page).

For this reason, the term ‘higher-level processing’ is often preferred when describing the use of contextual information, as against lower level decoding operations. Or a distinction is made between conceptual and perceptual processes.

The term ‘top-down’ is also sometimes used to refer to theories of reading or listening which hold that contextual information plays a more important part than perceptual. Again, this is misleading as it implies that a choice has to be made. Even ‘top-down’ accounts have to include at least some perceptual evidence. The issue is to establish how the two information sources interact and which one predomi nates in case of conflict.

There are conflicting views. Some commentators claim that top down information is only used for checking bottom-up. Some argue for bottom-up priority, with contextual evidence only invoked once sufficient bottom-up evidence has become available. Their case is based partly on the fact that bottom-up processing is more automatised than top-down, and therefore faster; and partly on the argument that too many sources of information impede rapid decision making. Other commentators favour a fully interactive model of listening or reading, contending that both sources of evidence are available throughout. They argue that it is more efficient to have all the information available at one time.

It is important to make a distinction between two different purposes for invoking contextual knowledge in listening and reading:

To compensate for gaps in understanding. In the case of the weak reader, the gaps might reflect weak decoding skills. In the case of the second language learner, they might be the result of a limited vocabulary or grammar or the inability to recognise known words in connected speech.

To enrich the meaning interpretation of what has been read or heard by bringing in world knowledge, knowledge of the discourse so far etc.

The second purpose characterises the more skilled listener/reader and the more advanced language learner. They have achieved a degree of automaticity in the way they decode language, which frees working memory resources and makes them available for considering the wider contextual implications of what is being read or heard.

See also: Context effects, Listening: higher-level processes, Reading: bottom-up vs top-down, Reading: higher-level processes, Speech perception: autonomous vs interactive

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Primary Metaphor Theory

Hiding and highlighting

The conceptual nature of metaphor

Invariance

Metaphors and image schemas

Metaphor systems

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Motivation for target and source

The unidirectionality of metaphor

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