Abstract
In this discussion paper, I review a number of common misconceptions about the phonological deficit theory (PDH) of dyslexia. These include the common but mistaken idea that the PDH is simply about phonemic awareness (PA), and, consequently, is a circular “pseudo”-explanation or epiphenomenon of reading difficulties. I argue that PA is only the “tip of the phonological iceberg” and that “deeper” spoken-language phonological impairments among dyslexics appear well before the onset of reading and even at birth. Furthermore, not even reading-specific expressions of phonological deficits—PA or pseudoword naming, can be considered circular if we clearly distinguish between reading proper—real meaning-bearing words, or real text, and the mechanisms (subskills) of reading development (such as phonological recoding). I also explain why an understanding of what constitutes an efficient writing system explains why phonology is necessarily a major source of variability in reading ability and hence a core deficit (or at least one core deficit) among struggling readers whether dyslexic or non-dyslexic. I also address the misguided notion that the PDH has now fallen out of favor because most dyslexia researchers have (largely) ceased studying phonological processing. I emphasize that acceptance of the PDH does not imply repudiation of other non-phonological hypotheses because the PDH does not claim to account for all the variance in reading ability/disability. Finally, I ask where neurobiology enters the picture and suggest that researchers need to exercise more caution in drawing their conclusions.
Highlights
The Phonological Deficit Hypothesis of Dyslexia: A Scientific Success Story The Phonological Deficit Hypothesis (PDH) of dyslexia, in many ways, is a model of true scientific progress. This success story began over half of century ago at Haskins Laboratories, New Haven, Connecticut, where unplanned and unanticipated discoveries about the nature of the speech code [1] lead to a new appreciation of the complexities of “extracting” phonemes from the speech stream [2] and the far-reaching implications of these insights with regard to the challenges of learning to read a writing system based on phonemic units [3,4,5]
Returning to the tip of the iceberg analogy, it is clear that once we look below the surface we see that, this ensemble of phonological deficits are true precursors or antecedents of reading disability/dyslexia in both a temporal and logical sense
The search continues for other non-phonological sources of variation in reading ability and disability/dyslexia because phonology is not the whole story
Summary
In addition to learning the specific symbol-sound mappings of the orthography being learned, the learner must “get inside words”, go below the level of meaning and penetrate their sound structure This phonological analysis or “meta-linguistic” awareness is an inescapable pre-requisite for literacy learning enabling the learner to exploit the combinatoriality of writing, decipher novel letter strings, match up spellings and pronunciations, and begin the process of building the orthographic lexicon by unitizing or chunking sub-lexical symbols into higher-order meaning units—the key to rapid automatic word recognition. Phonology is not, cannot be the whole story to reading ability and disability/dyslexia
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