The most common cause of early reading difficulties is a weakness in children’s phonological processing skills, the ability to recognize, manipulate, and use the sound structure of spoken language. Children with poor phonological processing skills have difficulty cracking the alphabetic code that connects the graphemes in written alphabetic languages to the phonemes in spoken language. These children lack an effective strategy for decoding an unfamiliar word when they encounter it in print. They tend to rely too heavily on contextual cues to guess the unfamiliar word rather than using knowledge of phonics to decode it. Consequently, their attempts to decode unfamiliar words result in many word-reading errors. Reading grade-level material is difficult, and many of these children begin to develop negative attitudes about reading, resulting in reduced opportunities to practice reading (Oka & Paris, 1986). Prior research has identified three interrelated clusters of phonological processing abilities: phonological awareness, phonological access to lexical store, and phonological memory (Wagner & Torgesen,1987).
Phonological awareness refers to the ability to detect or manipulate the sound structures of oral language. Research with a variety of populations, using diverse methods, has converged on the finding that phonological awareness plays a key role in the normal acquisition of reading (e.g., Adams, 1990; Byrne & Fielding-Barnsley, 1991; Stanovich, 1992; Wagner & Torgesen, 1987). Children who are better at detecting and manipulating syllables, rhymes, or phonemes are quicker to learn to read; this relation is present even after variability in reading skill due to factors such as IQ, receptive vocabulary, memory skills, and social class is partialled-out (e.g., Bryant, MacLean, Bradley, & Crossland, 1990;Wagner & Torgesen, 1987; Wagner, Torgesen, & Rashotte, 1994).
Phonological access to lexical store refers to the efficiency of retrieval of phonological codes from permanent memory (Wagner & Torgesen, 1987). In older children, lexical access typically is measured as the rate at which an array of letters, digits, or colors can be named. In younger children, lexical access may be measured as the rate at which an array of objects or colors can be named. Lexical access measures are significant predictors of growth in decoding skills in school-age children (Wagner et al., 1994, 1997), and appear to have an independent effect on growth in decoding above that of phonological sensitivity and phonological memory, consistent with the double deficit hypothesis (Bowers & Swanson, 1991; Kirby, Parrila, & Pfeiffer, 2003; Manis, Doi, & Bhadha, 2000; Schatschneider, Fletcher, Francis, Carlson, & Foorman, 2004).
Phonological memory refers to the coding of information in a sound based representation system for temporary storage (Baddeley, 1986) and is typically measured by immediate recall of verbally presented material (e.g., repetition of nonwords or digits). Results from studies by Wagner et al. (1994, 1997) indicate that phonological memory is a significant correlate of growth in decoding skills but that it does not provide unique predictive variance to growth in decoding beyond that provided by phonological awareness for school-age children.
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