How do children learn to read and what goes wrong for some children?

February 07th, 2012

Models of reading: The dual-route approach

There are a number of different models of how we read, the most appealing of which is Max Colheart’s Dual-Route Approach. 

This approach uses the terms “lexical” and “non-lexical” to describe two ways in which words can be read aloud. “Lexical” refers to a route where the word is familiar and recognition prompts direct access to a pre-existing representation of the word name that is then produced as speech. “Non-lexical” refers to a route used for novel or unfamiliar words. As unfamiliar words are, by definition, unrepresented in the brain’s lexicon, they cannot be read directly. They have to be decoded using knowledge of grapheme-phoneme (or “letter-sound”) conversion rules (GPCs).

Figure 1 shows the Dual-Route model. The visual features and the global form of the printed word shelf are recognised as a familiar word, which activates the orthographic representation of shelf in the Orthographic Lexicon, in turn activating the word’s name in the Phonological Lexicon, before activating the word’s meaning in the Semantic Lexicon. The 4 Sub-Lexical Phonological Representations (speech sounds) (i.e., /sh/ /e/ /l/ /f/) are then activated and produced as the spoken word shelf.

In contrast, gallimaufry will not be read directly by anyone other than those with exceptional large vocabularies, because most mere mortals will have no pre-existing Orthographic or Phonological representations for this very low-frequency word. Instead, the individual letters are analysed using knowledge of GPCs (e.g., g = /g/), the appropriate Sub-Lexical Phonological Representations are accessed, before finally, the sub-lexical units are reassembled as a word and translated to speech. There is a feedback system in operation in this process that allows access to the word’s meaning and learning of new words to take place.

Figure 1. An adapted Dual-Route model of reading showing the different pathways by which the know word shelf and the unknown word gallimaufry may be read aloud. Source http://www.maccs.mq.edu.au/~ssaunder/DRC/.

 

Skilled readers mostly use the Lexical route. They retain the ability to use the Sub-Lexical route (consider how you read gallimaufry and bioluminescence), it is just that they don’t need to – they have had enough experience with reading to have developed sufficient lexical knowledge. In contrast, young readers, and individuals struggling with reading , do not possess word-specific lexical knowledge in sufficient quantities. How then, do we teach this skill?

The goal of all word-reading instruction should be to assist students to read most words fluently, using the lexical route. But how do we do this? The answer lies in the development of the sub-lexical route.

The development of Sub-Lexical Reading

The following describes what we think might happen in learning to read. However, readers should note that we have a good idea of how skilled reading occurs but we actually don’t yet know how we learn to read.

Imagine that the young student destined to become a skilled reader has, by virtue of genetic fortune, all of the skills required to read. Then imagine that the following words are the first they ever attempt to read:

sit

pat

The skilled-reader-to-be has some recognition that words can be segmented into speech sounds (e.g., sit has three: /s/ /i/ /t/). This helps them map the written letters s, i t, p, a onto a speech sound (e.g., s = /s/). Acquiring these “letter-sound mappings” gives the student access to the Sub-Lexical reading route. They can read any word that has any combination of those five letters without the help of an adult (i.e., they can independently read words like tap, tip, sap, spit).

Research has shown us that we have to accurately identity a word between 4-12 times before it becomes what teachers refer to as a “sight word”. That is, before a strong enough representation of the visual form of the word and its name is formed to allow reading using the Lexical route. At this point, reading begins to speed up. The student no longer has to laboriously decode every word; fluent recognition frees up cognitive space and energy which can be used for other functions, such as comprehension and learning unusual spelling patterns.

The process seems to be different for the unskilled reader. For whatever reason, when they see the first words sit and pat they have difficulty recognising the relationship between the speech sounds in the words and the written letters used to represent them. Acquisition of “letter-sound mappings” is therefore delayed, preventing access to the Sub-Lexical reading route. When the young, or unskilled reader sees the words below, how then do they read them?

sap tip

at pit

They can’t accurately decode them using the Sub-Lexical route. Instead, they guess. In some cases the guess may be ‘educated’, but a guess all the same. Sometimes they will try to predict the word from the meaning or structure of the sentence. Often they will look at a picture to help with the printed words. They may also rely upon salient visual cues within the words, such as the initial letter, word length, or other obvious letters. It is possible that an unskilled reader will read “A fat cat sat on the mat” as “A big kitten was sitting on the floor”.

Despite common belief in education circles, using contextual cues is not only inaccurate, but damaging to students’ reading. Research has shown that contextual cues only provide 5-25% accuracy rates; and for the important content words in sentences the accuracy rate is towards the bottom of that range. In addition, because prediction from context avoids use of both the Lexical and Sub-lexical routes, even if the student guesses correctly, it does not count towards the 4-12 successful decoding attempts required to learn a word “by sight”. Using contextual cues is therefore self-defeating.

Teaching students to read

Reading is a complicated process that requires instruction in, among other things, phonological awareness, letter-knowledge, phonics, spelling, strategy development, vocabulary, grammatical awareness, and comprehension strategies. The Understanding Words programme is a good example of an evidence-based reading intervention.

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