Orthographies and dyslexia

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Dyslexia is a complex, lifelong disorder involving difficulty in learning to read or interpret words, letters and other symbols. Dyslexia does not affect general intelligence, but is often co-diagnosed with ADHD. [1] [2] There are at least three sub-types of dyslexia that have been recognized by researchers: orthographic, or surface dyslexia, phonological dyslexia and mixed dyslexia where individuals exhibit symptoms of both orthographic and phonological dyslexia. [3] Studies have shown that dyslexia is genetic and can be passed down through families, but it is important to note that, although a genetic disorder, there is no specific locus in the brain for reading and writing. The human brain does have language centers (for spoken and gestural communication), but written language is a cultural artifact, and a very complex one requiring brain regions designed to recognize and interpret written symbols as representations of language in rapid synchronization. The complexity of the system and the lack of genetic predisposition for it is one possible explanation for the difficulty in acquiring and understanding written language. [4]

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Furthermore, recent evidence has found that there are certain genes responsible for causing dyslexia. [5] Research also suggests a clear genetic basis for developmental dyslexia with abnormalities in certain language areas of the brain. [6] [7] However, there is also evidence that orthography, the correspondence between the language's phonemes (sound units) and its graphemes (characters, symbols, letters), plays a significant role in the type and frequency of dyslexia's manifestations. [7] Some psycholinguists believe that the complexity of a language's orthography (whether it has a high phoneme-grapheme correspondence or an irregular correspondence in which sounds do not clearly map to symbols) affects the severity and occurrence of dyslexia, postulating that a more regular system would reduce the number of cases of dyslexia and/or the severity of symptoms. [8]

Current psycholinguistic models of dyslexia are "largely developed on the basis of alphabetic writing systems such as English", [9] but the amount of research on some logographic orthographies, Chinese in particular, [10] is also fairly significant. Unfortunately, little research has been done on syllabic writing systems, and "cross-linguistic studies of the acquired dyslexia and dysgraphias are scarce." [9]

Dyslexia and orthographic features

Orthographic Dyslexia

Orthographic dyslexia, a subtype of dyslexia, results in difficulty decoding and encoding skills due to slow and inaccurate rates of storing word and letter formations into memory. Orthographic dyslexics have difficulty in storing mental representation of words, especially phonetically irregular words such as word spellings that end in -ight ("light" and "sight"). The problems underlying this type of dyslexia are related directly to memory and coding skills that allow representation of printed letters and words, not to poor phonological processing. [11]

This type of dyslexia is also termed surface dyslexia because people with this type have the inability to recognize words simply on a visual basis. Words that are misspelled cause the readers difficulty because they attempt to sound out the words by looking at each individual letter rather than the word as a whole. [12] So a reader might read the word "cat" and pronounce the "c" as a hard "c" but then read the word "ice" and pronounce the "c" as a hard "c" as well because they are sounding out each individual phoneme rather than just recognizing the word "ice" in its entirety.

Despite intervention, children with orthographic dyslexia continually have lower achievement reading levels when compared to their peers. Additionally, children show a greater difficulty throughout schooling when spelling words with irregular or unusual orthographies when compared to their other children. Research also shows that dyslexic children have primary difficulties in phonological processing and secondary difficulties in orthographic processing, aiding to the distinction of two subtypes. [13]

The effects of orthographic depth on dyslexia

The complexity of a language's orthography is directly related to the difficulty of learning to read in that language. Orthographic complexity also contributes to how dyslexia manifests in readers of different languages. [14]

Deep orthographies are writing systems, such as those of English and Arabic, that do not have a one-to-one correspondence between sounds (phonemes) and the letters (graphemes) that represent them.

Shallow orthographies, such as Italian and Finnish, have a close relationship between graphemes and phonemes, and the spelling of words is very consistent. With shallow orthographies, new readers have few problems learning to decode words and as a result children learn to read relatively quickly. Most dyslexic readers of shallow orthographic systems learn to decode words with relative ease compared to dyslexics using deep orthographies, though they continue to have difficulty with reading fluency and comprehension. [8] The hallmark system of dyslexia in a shallow orthography is a comparatively slow speed of rapid automatized naming.

Writing and drawing performed by a child with dyslexia, displaying common behavioral symptoms. Dislexia.jpg
Writing and drawing performed by a child with dyslexia, displaying common behavioral symptoms.

For languages with relatively deep orthographies, such as English and French, readers have greater difficulty learning to decode new words than languages with shallow orthographies. As a result, children's reading achievement levels are lower. [15] Research has shown that the hallmark symptoms of dyslexia in a deep orthography are a deficit in phonological awareness and difficulty reading words at grade level. [16] For these dyslexic readers, learning to decode words may take a long time—indeed, in the deepest orthographies a distinctive symptom of dyslexia is the inability to read at the word level—but many dyslexic readers have fewer problems with fluency and comprehension once some level of decoding has been mastered.

Studies between the English and German (which has a shallower orthography than English) languages have shown that the greater depth of the English orthography has a "marked adverse effect on reading skills" among children with dyslexia, though the dyslexics in these studies still mostly underperformed compared to control groups. [8] [17] Other research, however, has suggested that all children with dyslexia still have the same reading difficulties despite different orthographies, including reading speed deficit and slow decoding mechanisms. [7] These findings suggest that orthographic differences do not significantly impact the main difficulties those with dyslexia experience. Complicating this is the fact that different dyslexia tests often follow variable criteria.

Dyslexia in different types of orthographies

There are a number of different types of writing systems, or orthographies, and they do not necessarily depend on the same neurological skill sets. [18] As a result, certain dyslexic deficits may be more pronounced in some orthographies than in others. For example, in alphabetic languages, phonological awareness is highly predictive of reading ability. But in Chinese (a logographic system), orthographic awareness and motor programming are highly predictive of reading ability. [19] However, literature reviews show that the type of orthography has little effect on rates of dyslexia compared to orthographic depth. For example, Chinese, which is a fully logographic orthography, has comparable rates of dyslexia (3.9%) to that of shallow alphabetic orthographies such as Italian (3.2%) while English, which is a deep alphabetic orthography, has much higher rates of up to 10%. [20]

TypeEach symbol representsExamplePredictive skill
Logographic word or morpheme Chinese characters Orthographic awareness, motor programming, naming speed
Syllabic syllable Japanese kana
Alphabetic phoneme (consonant or vowel) Latin alphabet Phonological awareness, naming speed
Abugida phoneme (consonant+vowel)Indian Devanāgarī Unknown
Abjad phoneme (consonant) Arabic alphabet Unknown
Featural phonetic featureKorean hangul Unknown

Dyslexia in alphabetic orthographies

Most of the current research on dyslexia focuses on alphabetic orthography. [9]

Alphabetic writing systems vary significantly in the depth of their orthography. English and French are considered deep orthographies in comparison to Spanish and Italian which are shallow orthographies. A deep orthography like English has letters or letter combinations that do not reliably map to specific phonemes/sound units, and so are ambiguous in terms of the sounds that they represent whereas a transparent or shallow orthography has symbols that (more) uniquely map to sounds, ideally in a one-to-one correspondence or at least with limited or clearly signified (as with accent marks or other distinguishing features) variation. Literacy studies have shown that even for children without reading difficulties like dyslexia, a more transparent orthography is learned more quickly and more easily; this is true across language systems (syllabic, alphabetic, and logographic), and between shallow and deep alphabetic languages. [21]

In cross-language studies, Aro and Wimmer report differences in developmental reading skills across several alphabetic orthographies. Among those tested, English children achieved only 50% accuracy in pseudoword testing by the end of first grade and did not attain high accuracy until fourth grade. However, in the same test, French, German, Dutch, Spanish, Swedish, and Finnish children all achieved scores approaching 85% and 90% in Grade 1 and Grade 4, respectively. [22] This research provides evidence that orthographic irregularities, such as the "complex grapheme-phoneme relations" found in English, present significant difficulties in the reading development of children. [22] However, the methodology of the experiment leaves doubt as to whether the scores correlate to actual reading ability on real words.

However, there is little evidence that a more "regular" orthographic system would significantly diminish the number of dyslexia cases. Because there is also a visual aspect to dyslexia, affected children often show symptoms such as mirror letter reversal (e.g. confusing "b" and "d"), which can manifest in any language regardless of orthographic depth.)

Dyslexia in logographic orthographies

Logographic writing systems (such as Chinese characters and Cuneiform) differ significantly from alphabetic systems in that the graphemes of a logographic system are logograms; that is, written characters represent morphemes, rather than phonemes. English is sometimes considered a partially logographic orthography. As a result, logographic systems require a comparatively large number of unique characters. This means that development of reading and writing skills in logographic systems depends more heavily on visual memorization than in alphabetic systems. Thus dyslexics, who often rely on grapheme memorization to cope with phonological awareness deficits, [23] [24] may show reduced difficulty in acquiring a language which uses a logographic system. [25] However, logograms offer fewer phonological cues than alphabets and so have a more irregular orthography/grapheme-to-phoneme correspondence when compared with a more transparent system like an alphabet or syllabary.

Archaic Chinese logograms XiaozhuanQinquan sized.jpg
Archaic Chinese logograms

Chinese orthographies

Chinese children dyslexia often have both a visuospatial and phonological disorder which are independent of one another. This implies that unlike alphabetic orthographies where only a phonological or visuospatial disorder alone can cause dyslexia, Chinese children must suffer from both disorders for dyslexia to manifest. [26] This could be one possible explanation for the comparatively low rates of dyslexia in Chinese children. [20]

With alphabetic writing systems, phonological awareness plays a central role in reading acquisition; while phonological awareness in Chinese is much less important. Rather, reading in Chinese is strongly related to a child's writing skills, which depend on orthographic awareness and on motor memory. In handling alphabetic languages with deep orthographies, the child must cope with having more than one spelling to represent a sound. In spoken Chinese, a single syllable is used in many different words, and a Chinese child must cope with having many written characters that represent the same syllable. [21]

Further complicating the Chinese writing system, the Chinese character is made up of strokes and sub-character components, substantially increasing visual complexity. Thus orthographic processing is an important aspect of reading. Deficient orthography-to-meaning mapping can lead to reading disability. A key strategy in teaching children to read is to have children repeatedly write samples of single characters, thus building the child's awareness of a character's internal structure (orthographic awareness). [19]

Rapid naming is one of the best single predictors of dyslexia in all languages tested, including both alphabetic and character-based writing systems. [19] [27] There is some evidence that the means of deciphering characters differs between logographic and alphabetic writing systems[ clarification needed ] in the brain: logographic systems echo map-reading skills.

Dyslexia in syllabic orthographies

In a syllabary, written characters represent spoken syllables, whereas alphabetic systems use characters/letters to represent separate phonemes. [21] A symbol in a syllabary typically has the canonical shape of a consonant-vowel (CV) combination. In the Japanese syllabaries, hiragana and katakana, there is a nearly one-to-one correspondence between morae and characters. The transparency of these syllabaries is the reason for their use in first teaching Japanese children to read before advancing to the complex logographic system of kanji, and by the age of five, prior to any official reading education, 89% of Japanese children can read the majority (60 or more out of 71) of hiragana characters. [21]

Syllabary orthographies, like English orthography, can also be very irregular[ clarification needed ]. However, little research has been done on how dyslexia presents in syllabic systems. One possible reason for this is that because of the different ways that dyslexia can present, the disorder may go unnoticed or not be recognized. A literacy study on children without reading disabilities found that syllabic scripts like Japanese katakana and hiragana, which are very transparent orthographically, are learned more quickly and with better proficiency than more orthographically opaque languages, followed in ease of use and learning by shallow alphabetic scripts that also have many phonological cues, then by complex alphabetic scripts that have irregular orthography (like English), and then by logographic scripts like kanji which have almost no phonological cues. [21]

See also

Related Research Articles

<span class="mw-page-title-main">Dyslexia</span> Specific learning disability characterized by troubles with reading

Dyslexia, previously known as word blindness, is a learning disability that affects either reading or writing. Different people are affected to different degrees. Problems may include difficulties in spelling words, reading quickly, writing words, "sounding out" words in the head, pronouncing words when reading aloud and understanding what one reads. Often these difficulties are first noticed at school. The difficulties are involuntary, and people with this disorder have a normal desire to learn. People with dyslexia have higher rates of attention deficit hyperactivity disorder (ADHD), developmental language disorders, and difficulties with numbers.

<span class="mw-page-title-main">Grapheme</span> Smallest functional written unit

In linguistics, a grapheme is the smallest functional unit of a writing system. The word grapheme is derived from Ancient Greek gráphō ('write'), and the suffix -eme by analogy with phoneme and other emic units. The study of graphemes is called graphemics. The concept of graphemes is abstract and similar to the notion in computing of a character. By comparison, a specific shape that represents any particular grapheme in a given typeface is called a glyph.

An orthography is a set of conventions for writing a language, including norms of spelling, punctuation, word boundaries, capitalization, hyphenation, and emphasis.

In the linguistic study of written languages, a syllabary is a set of written symbols that represent the syllables or moras which make up words.

<span class="mw-page-title-main">Hyperlexia</span> Significantly advanced reading ability in children

Hyperlexia is a syndrome characterized by a child's precocious ability to read. It was initially identified by Norman E. Silberberg and Margaret C. Silberberg (1967), who defined it as the precocious ability to read words without prior training in learning to read, typically before the age of five. They indicated that children with hyperlexia have a significantly higher word-decoding ability than their reading comprehension levels. Children with hyperlexia also present with an intense fascination for written material at a very early age.

<span class="mw-page-title-main">Logogram</span> Grapheme which represents a word or a morpheme

In a written language, a logogram, also logograph or lexigraph, is a written character that represents a semantic component of a language, such as a word or morpheme. Chinese characters as used in Chinese as well as other languages are logograms, as are Egyptian hieroglyphs and characters in cuneiform script. A writing system that primarily uses logograms is called a logography. Non-logographic writing systems, such as alphabets and syllabaries, are phonemic: their individual symbols represent sounds directly and lack any inherent meaning. However, all known logographies have some phonetic component, generally based on the rebus principle, and the addition of a phonetic component to pure ideographs is considered to be a key innovation in enabling the writing system to adequately encode human language.

A phonemic orthography is an orthography in which the graphemes correspond consistently to the language's phonemes, or more generally to the language's diaphonemes. Natural languages rarely have perfectly phonemic orthographies; a high degree of grapheme–phoneme correspondence can be expected in orthographies based on alphabetic writing systems, but they differ in how complete this correspondence is. English orthography, for example, is alphabetic but highly nonphonemic.

According to the alphabetic principle, letters and combinations of letters are the symbols used to represent the speech sounds of a language based on systematic and predictable relationships between written letters, symbols, and spoken words. The alphabetic principle is the foundation of any alphabetic writing system. In the education field, it is known as the alphabetic code.

<span class="mw-page-title-main">Management of dyslexia</span>

Management of dyslexia depends on a multitude of variables; there is no one specific strategy or set of strategies that will work for all who have dyslexia.

Deep dyslexia is a form of dyslexia that disrupts reading processes. Deep dyslexia may occur as a result of a head injury, stroke, disease, or operation. This injury results in the occurrence of semantic errors during reading and the impairment of nonword reading.

The history of dyslexia research spans from the late 1800s to the present.

Dyslexia is a reading disorder wherein an individual experiences trouble with reading. Individuals with dyslexia have normal levels of intelligence but can exhibit difficulties with spelling, reading fluency, pronunciation, "sounding out" words, writing out words, and reading comprehension. The neurological nature and underlying causes of dyslexia are an active area of research. However, some experts believe that the distinction of dyslexia as a separate reading disorder and therefore recognized disability is a topic of some controversy.

<span class="mw-page-title-main">Characteristics of dyslexia</span>

Dyslexia is a disorder characterized by problems with the visual notation of speech, which in most languages of European origin are problems with alphabet writing systems which have a phonetic construction. Examples of these issues can be problems speaking in full sentences, problems correctly articulating Rs and Ls as well as Ms and Ns, mixing up sounds in multi-syllabic words, problems of immature speech such as "wed and gween" instead of "red and green".

A writing system comprises a set of symbols, called a script, as well as the rules by which the script represents a particular language. The earliest writing was invented during the late 4th millennium BC. Throughout history, each writing system invented without prior knowledge of writing gradually evolved from a system of proto-writing that included a small number of ideographs, which were not fully capable of encoding spoken language, and lacked the ability to express a broad range of ideas.

The orthographic depth of an alphabetic orthography indicates the degree to which a written language deviates from simple one-to-one letter–phoneme correspondence. It depends on how easy it is to predict the pronunciation of a word based on its spelling: shallow orthographies are easy to pronounce based on the written word, and deep orthographies are difficult to pronounce based on how they are written.

Rapid automatized naming (RAN) is a task that measures how quickly individuals can name aloud objects, pictures, colors, or symbols. Variations in rapid automatized naming time in children provide a strong predictor of their later ability to read, and is independent from other predictors such as phonological awareness, verbal IQ, and existing reading skills. Importantly, rapid automatized naming of pictures and letters can predict later reading abilities for pre-literate children.

Surface dyslexia is a type of dyslexia, or reading disorder. According to Marshall & Newcombe's (1973) and McCarthy & Warrington's study (1990), patients with this kind of disorder cannot recognize a word as a whole due to the damage of the left parietal or temporal lobe. Individuals with surface dyslexia are unable to recognize a word as a whole word and retrieve its pronunciation from memory. Rather, individuals with surface dyslexia rely on pronunciation rules. Thus, patients with this particular type of reading disorder read non-words fluently, like "yatchet", but struggle with words that defy pronunciation rules. For example, a patient with surface dyslexia can correctly read regular words like "mint", but will fail when presented with a word that disobeys typical pronunciation rules, like "pint". Often, semantic knowledge is preserved in individuals with surface dyslexia.

The dual-route theory of reading aloud was first described in the early 1970s. This theory suggests that two separate mental mechanisms, or cognitive routes, are involved in reading aloud, with output of both mechanisms contributing to the pronunciation of a written stimulus.

The following outline is provided as an overview of and topical guide to dyslexia:

References

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