ELT Journal

doi:10.1093/elt/53.4.338 53:338-339, 1999. ELT J

John Field ‘Bottom-up’ and ‘top-down’

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Key concepts in ELT

'Bottom-up' and 'top-down'In accounts of foreign-language listening andreading, perceptual information is oftendescribed as 'bottom-up', while informationprovided by context is said to be 'top-down'.The terms have been borrowed from cognitivepsychology, but derive originally from computerscience, where they distinguish processes that aredata-driven from those that are knowledge-driven.

Underlying the metaphors 'top' and 'bottom' is ahierarchical view of the stages through whichlistening or reading proceeds. In listening, thelowest level (i.e. the smallest unit) is the phoneticfeature. A simple analysis might present thelistener as combining groups of features intophonemes, phonemes into syllables, syllables intowords, words into clauses, and clauses intopropositions. At the 'top' is the overall meaningof the utterance, into which new information isintegrated as it emerges. Drawing on this conceptof levels of processing, many ELT commentatorspresent a picture of listening and reading in whichbottom-up information from the signal isassembled step by step, and is influencedthroughout by top-down information fromcontext.

The truth is rather more complex. First, it is notcertain that bottom-up processing involves all thelevels described. Some psychologists believe thatwe process speech into syllables without passingthrough a phonemic level; others that we constructwords directly from phonetic features. Nor doesbottom-up processing deal with one level at atime. There is evidence that in listening it takesplace at a delay of only a quarter of a secondbehind the speaker—which implies that the tasksof analysing the phonetic signal, identifying words,and assembling sentences must all be going on inparallel.

A quarter of a second is roughly the length of anEnglish syllable—so the listener often begins theprocessing of a word before the speaker hasfinished saying it. The listener forms hypotheses asto the identity of the word being uttered, whichare said to be activated to different degreesaccording to how closely they match the signal.The candidates compete with each other until,when the evidence is complete, one of themoutstrips the rest.

Like 'bottom-up' processing, 'top-down' is morecomplex than is sometimes suggested. Contextualinformation can come from many differentsources: from knowledge of the speaker/writer orfrom knowledge of the world; from analogy with aprevious situation or from the meaning that hasbeen built up so far. It can be derived from aschema, an expectation set up before reading orlistening; it can take the form of spreadingactivation, where one word sparks offassociations with others; or it can be based uponthe probability of one word following another. It isimportant to specify which of these cues isintended when the expression 'top-down' isemployed.

Also unspecified in many accounts of L2 readingand listening is the way in which bottom-up andtop-down processes interact. Does one occurbefore the other, or do they operatesimultaneously? The evidence from LI researchis contradictory. Some findings suggest thatcontextual information is invoked beforeperception, helping us to anticipate words;others, that it becomes available during theperceptual process; others, that it is onlyemployed after a word has been identified.Goodman's much-quoted view (1970) thatsuccessful readers guess ahead using currentcontext has not been conclusively demonstrated.

Some researchers argue for completely interactivemodels of listening and reading, in which top-down and bottom-up processes extendsimultaneously through all levels. In support ofsuch models, they cite evidence of wordsuperiority effects, where knowledge of completewords influences the way we perceive sounds orletters. This kind of effect is appropriatelydescribed as 'top-down' since it involvesknowledge at a higher level affecting processingat a lower. So note that the term 'top-down' is notalways synonymous with 'contextual'.

Finally, the vexed question of the use of bottom-up and top-down information by foreign-languagelearners. A truism of ELT has it that low-levellisteners and readers become fixated at word level,and do not have enough spare attentional capacityto construct global meaning. In truth, learnersappear to make considerable use of top-downinformation: employing it compensatorily to pluggaps where their understanding of a text isincomplete. The best account of this process is

338 ELT Journal Volume 53/4 October 1999 © Oxford University Press 1999

provided by Stanovich's interactive-compensatorymechanism (1980), originally formulated for LIreading. Stanovich suggests that we use contextualinformation to make up for unreliability in thesignal (bad handwriting, for example, or ambientnoise). The more flawed the bottom-upinformation, the more we draw upon cues fromtop-down sources. This seems to describeaccurately the way in which L2 learners resort totop-down inferencing when understanding isimpaired by limited vocabulary or syntax. Thestrategy may be more common in listening than inreading: see Lund (1991).

For accounts of the role of bottom-up and top-down processes in LI reading, see Oakhill andGarnham (1988), and Chapters 2-3 of Perfetti(1985). Currently, the most influential model of LIlistening is the fully-interactive Cohort Model(Marslen-Wilson 1987).

ReferencesGoodman, K. S. 1970.: 'Reading: A psycholinguis-

tic guessing game' in H. Singer and R. B.Ruddell (eds.). Theoretical Models and Pro-cesses of Reading. Newark, DE: InternationalReading Association.

Lund, R. J. 1991: 'A comparison of secondlanguage listening and reading comprehension'.Modern Language Journal 75: 196-204.

Marslen-Wilson, W. D. 1987: 'Functional paralle-lism in spoken word recognition'. Cognition 25.

Oakhill, J. and A. Garnham. 1988. Becoming aSkilled Reader. Oxford: Blackwell.

Perfetti, C. A. 1985. Reading Ability. New York:Oxford University Press.

Stanovich, K. E. 1980: 'Toward an interactive-compensatory model of individual differences inthe development of reading fluency'. ReadingResearch Quarterly 16: 32-71.

The authorJohn Field has a long-term interest in skillsapproaches in ELT. His publications includelistening and study skills materials, a BBC radioseries for beginners, distance-learning materialsfor Chinese television, and national secondaryschool coursebooks for Saudi Arabia. He hastrained teachers in Europe, the Middle East, theFar East, and Africa. He is about to complete aPhD on listening at Cambridge University, andlectures on the MA course in ELT and AppliedLinguistics at Kings College London.E-mail: jcfl000@dircon.co.uk

Key concepts in ELT 339