Study of Developmental Phonological Dyslexia

Disorder description

Dyslexia is a condition in a which an individual has language impairments and/or reading difficulties. The term “dyslexia” was developed by Rudolf Berlin in 1887 in belief that a form of inability to read was caused by brain lesions. He distinguished between severe damage to the brain (alexia), and partial damage to the brain (dyslexia). In this, Berlin went on to focus on the between two main categories of effects of a physical trauma: acquired and developmental dyslexia (Wager, 1973). It is important to understand the differences between these two types, as it benefits in understanding the differing effects they have on individuals.

Acquired dyslexia refers to a reading impairment present in an individual who once had the ability to read normally, however lost this due to brain damage. On the other hand, developmental dyslexia occurs when an individual (often a child) has a reading impairment due to issues in their developmental stages of life, thus was never initially able to read normally. It is a condition which affects one’s reading, writing, and spelling skills, and impacts the ability of an individual to understand and interpret language. It is imperative to note that dyslexia doesn’t determine one’s intelligence level nor does it control one’s visual capacity.

Reading is a complex process, and reading impairments arise from deficits in different aspects. Also, different kinds of dyslexia can uniquely affect individuals. The process of reading entails two key processes: ‘lexical’ and ‘non-lexical’ skills. This is evident in the dual-route model developed by Max Coltheart in 1978. This model explains the process of how one reads from letters and words from print, to how they understand and interpret it to produce phonation/speech. The lexical route (left-hand side) displays the whole word aspect of reading in which an individual can recognize the word, it’s meaning, and its phonic requirements then produce speech. The non-lexical (right-hand side) is associated with the letter-sound rules which explores an individual’s ability to work with letters and sounds they interpret from seeing a word, and thus convert it to speech (Ziegler et al, 2008).

Case-study description

The case study chosen “A case study of developmental phonological dyslexia” (Temple & Marshall, 1983) explores a subject H.M whose reading abilities are thoroughly analyzed to understand her condition. By doing so, researchers were able to gather information from her test results, draw out conclusions, and synthesize hypothesis’. H.M is a 17-year-old girl who is of good average intelligence, with a reading age of 10 years 11 months. She presents difficulty in non-word reading in comparison to word reading, in which she cannot read any long non-words or any unusual long words. This is evident through her inability to read words where the stimuli are distorted enough to limit global perception. The case study primarily focuses on H.M.’s phonological inabilities, as well as other errors in her reading such as derivational or visual paralexias.

The features and characteristics found in the results of H.M.’s various tests found to be similar and consistent with other reported cases of acquired phonological dyslexia. The case study confidently diagnoses H.M as a developmental phonological dyslexic. The case study begins with context on the history, features, definitions, and explanations of dyslexia to allow the readers to first gain an adequate insight on dyslexia. The focus then turns on the case report where more detail on the subject is given, and intelligence/capabilities/abilities are explained and compared to those of the average child e.g. H.M.’s verbal and performance test scores. The case report breaks down the analysis of H.M through sub-categories such as ‘non-word reading’, ‘word reading’, ‘spelling and writing’, and ‘further tests’ (Temple & Marshall, 1983).

The case study explicitly explores the features, processes, and explanations as to why various tests were given to H.M. This allows readers to understand how H.M.’s particular case of phonological dyslexia compares to other similar reported cases studies, or other types of dyslexia. Cognitive theory description The dual-route theory developed by Coltheart is a universal model used by researchers, psychologists, sociologists and cognitive scientists to deepen their understanding of reading processes and impairments. The model displays how two major routes (lexical and non-lexical) explain the process of an individual initially visualizing and identifying printed letters, to producing speech sounds from them.

Reading impairments arise when there becomes an issue in one or both routes. With the two major routes, hence are two distinct conditions associated with them: phonological (non-lexical route) and surface dyslexia (lexical route). The lexical route consists of three major aspects which help the individual to produce speech. The first step is access to the written word store which holds the recognition of familiar words. When the printed letters are identified, the individual can access a store of knowledge and memory where the representation of letters can be constructed. Inability to access this written word store will result in a condition known as surface dyslexia where the individual is poor in whole word reading (i.e. sight vocabulary). Following, is access to the word meaning store where when affected, it is usually a case of hyperlexia where the individual can accurately read aloud the word however is unable to comprehend its meaning.

The spoken word store is the last step of the lexical route where once the individual has accessed both a word’s familiarity and meaning, they can to link these to the word’s pronunciation and thus produce speech. The non-lexical route consists of one part: letter-sound rules. The production of speech stems from the individual’s ability to sound-out letters and construct words based on letter-sound rules. For example, the understanding of how the individual letters ‘d’, ‘o’, and ‘g’ form to pronounce the word ‘dog’ in its phonic sense. When this process of the dual route model becomes deficit, it is known as phonological dyslexia where the individual has poor knowledge of letter-sound rules thus poor ability in non-lexical reading. It is evident in individuals who struggle to read nonsense words where they tend to read these words as the most similar looking word. These are known as “lexicalization errors”.

Evidence

In the case study, the subject H.M. is diagnosed as a developmental phonological dyslexic. We can then say that her condition stems from a deficit in her non-lexical route. She has trouble in her grapheme-phoneme rules thus inhibiting her from understanding the relationship between how letters look and how they sound. Phonological dyslexia occur when there is poor knowledge of letter-sound rules, thus poor non-lexical reading. Difficulty in reading nonsense words in comparison to reading words is common to acquired phonological dyslexics.

H.M.’s nonword reading was shown to be poor as she relies on her lexical route of word familiarity and meaning, thus nonsense words are too foreign for her apprehension. H.M.’s non-word reading abilities were tested using 50 (25 word and 25 non-word) stimuli, where the non-word differentiated from the word by only one letter e.g. street : streed. H.M. was required to read each word correctly, where she only read 9 of the non-words correctly (Temple & Marshall, 1983). H.M relies on her lexical route thus memorization is key to her reading abilities, as she states ‘that’s the way I learn to read. I can’t do it any other way.’ When asked the value of good memory in assisting the reading of new words. H.M. is said to have “at least average intelligence and above average oral vocabulary”, as dyslexics are not lacking in their intelligence levels (Temple & Marshall, 1983).

The errors made in phonological dyslexia are generally categorized into two types; derivational or visual. H.M. is said to have most of her reading errors be both. A derivational error is where the subject’s error stems from a common root of the given stimuli whereas a visual error is where the subject’s error originates from a visual similarity to the stimuli. In H.M.’s case where she was presented with three hundred and forty-six words, two hundred and ninety-two (84%) were read correctly. There were several errors present, both being derivational (24%) and visual (41%) (Temple & Marshall, 1983).

Thus, it is evident that H.M.’s symptoms coincide with the theoretical symptoms of phonological dyslexics. Conclusion In conclusion, the dual route theory is a comprehensive, and highly accurate model in which case studies such as H.M.’s can be based on. Having a model that can explain the process of skilled reading and its components, allows us to identify the origins and causes for types of dyslexia. It is important to understand that most cases of dyslexia will have more than one component of the dual-route model affected. Thus, individuals such as H.M. can experience various symptoms that do and don’t account for her condition.

The understanding of dyslexics and dyslexia are significantly increased using theories such as the dual-route theory as it serves as a standardized model to which different diagnosis’ can compare to. There is still a great deal of research that needs to be done to extend current knowledge on the causes, effects, identification, characteristics, and treatments/interventions for dyslexia. Many skills tests exist to distinguish dyslexic patients and with more being developed, the accuracy of diagnosis will improve. Though theories and models prove highly effective in explaining circumstances, further research into the correlation between individuality and dyslexia symptoms will deepen our understanding of how we can better diagnose and thus treat dyslexic patients.

Reference List:

1. Temple, C., & Marshall, J. (1983). A case study of developmental phonological dyslexia. British Journal Of Psychology, 74(4), 517-533. doi: 10.1111/j.2044-8295.1983.tb01883.
2. Wagner, R. (1973). 5. Rudolf berlin: Originator of the term dyslexia. Bulletin Of The Orton Society, 23(1), 57-63. doi: 10.1007/bf02653841
3. Wu, D. (2002). A Third Route for Reading? Implications from a Case of Phonological Dyslexia. Neurocase, 8(4), 274-293. doi: 10.1093/neucas/8.4.274
4. Ziegler, J., Caste