Top Down vs Bottom Up Processing

Top down and bottom up processing

The way in which we process (and therefore understand) written and spoken texts is often described as either top-down or bottom-up.

What is top-down processing?

Top-down processing is the idea that to process and understand a text we start with “higher-level” features – background knowledge, context, overall meaning – and proceed through a series of steps “down” to “lower-level” semantic, syntactical and phonological features.

This contextual information at the top can come from knowledge about the world or the speaker/writer, from a mental image or expectation set up before or during listening or reading (often called a schema), or from predictions based on the probability of one word following another.

What is bottom-up processing?

To process and understand a text with bottom-up processing, we start by recognising phonemes, combining these into syllables, syllables into words, words into clauses, and so on “up” to contextual and background information.

Background knowledge
– Factual
– Cultural
– How language is used in texts
WORLD VIEW

Schematic knowledge

↑ ↓ ↑ ↓
Knowledge of the situation and context Context
↑ ↓ ↑ ↓
Linguistic knowledge
– Semantic
– Syntactic
– Phonological
Linguistic knowledge

LINGUISTIC VIEW

Do language learners use top-down or bottom-up processing?

Let’s use the example of watching the TV news. In our first language, we probably make use primarily of top-down processing. Our previous experience of watching TV news gives us some knowledge and expectations from which to make predictions about the likely content, as well as the style of language that will likely be used by presenters and journalists. As a news item starts, we may recognise it as an ongoing story, and call upon our knowledge of the story’s context. From there, we progress to “lower level” features to understand the finer details of the story.

L2 learners use more of a combination of bottom-up and top-down processing. They may compensate for a lack of vocabulary by using top-down cues about the context, but often rely too heavily on bottom-up processing at the expense of these cues, focusing on individual words and sentences. We can help them make more use of top-down cues with classroom activities focusing on this.

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