‘Bottom-up’ and ‘top-down’ In accounts of foreign-language listening and reading, perceptual information is often described as ‘bottom-up’, while information provided by context is said to be ‘top-down’. 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.
Underlying the metaphors ‘top’ and ‘bottom’ is a hierarchical view of the stages through which listening or reading proceeds. In listening, the lowest level (i.e. the smallest unit) is the phonetic feature. A simple analysis might present the listener as combining groups of features into phonemes, phonemes into syllables, syllables into words, words into clauses, and clauses into propositions. At the ‘top’ is the overall meaning of the utterance, into which new information is integrated as it emerges. Drawing on this concept of levels of processing, many ELT commentators present a picture of listening and reading in which bottom-up information from the signal is assembled step by step, and is influenced throughout by top-down information from context.