is a disorder characterized by problems with the visualnotation of speech, which in most languages of European origin are problems with alphabetwriting 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 "wed and gween" instead of "red and green". The characteristics of dyslexia have been identified mainly from research in languages with alphabetic writing systems, primarily English. However, many of these characteristic may be transferable to other types of writing systems. The causes of dyslexia are not agreed upon, although the consensus of neuroscientists believe dyslexia is a phonological processing disorder and that dyslexics have reading difficulties because they are unable to see or hear a word, break it down to discrete sounds, and then associate each sound with letters that make up the word. Some researchers believe that a subset of dyslexics have visual deficits in addition to deficits in phoneme processing, but this view is not universally accepted. In any case, there is evidence that dyslexics literally "see" letters backward or in reverse order within words. Poor working memory is another reason for those with dyslexia have difficulties remembering new vocabulary words. Verbal instructions are also a struggle. The capacity of the working memory is not enough due to trying to remember how commonly used words are spelled or even recognized them. Reading is done by memory rather than by sound.
Listening, speech and language
Some shared symptoms of the speech or hearing deficits and dyslexia:
Confusion with before/after, right/left, and so on
Difficulty learning the alphabet
Difficulty with word retrieval or naming problems
Difficulty identifying or generating rhyming words, or counting syllables in words
Difficulty with hearing and manipulating sounds in words
Difficulty distinguishing different sounds in words
Difficulty associating individual words with their correct meanings
Difficulty with time keeping and concept of time
Confusion with combinations of words
Difficulty in organization skills
The identification of these factors results from the study of patterns across many clinical observations of dyslexic children. In the UK, Thomas Richard Miles was important in such work and his observations led him to develop the Bangor Dyslexia Diagnostic Test.
Reading and spelling
Spelling errors — Because of difficulty learning letter-sound correspondences, individuals with dyslexia might tend to misspell words, or leave vowels out of words.
Letter order - People with dyslexia may also reverse the order of two letters especially when the final, incorrect, word looks similar to the intended word.
Letter addition/subtraction - People with dyslexia may perceive a word with letters added, subtracted, or repeated. This can lead to confusion between two words containing most of the same letters.
Highly phoneticized spelling - People with dyslexia also commonly spell words inconsistently, but in a highly phonetic form such as writing "shud" for "should". Dyslexic individuals also typically have difficulty distinguishing among homophones such as "their" and "there".
Vocabulary - Having a small written vocabulary, even if they have a large spoken vocabulary.
Seeing words backwards sometimes - a person sometimes might see the words backwards.
Because of literacy problems, an individual with dyslexia may have difficulty with handwriting. This can involve slower writing speed than average, poor handwriting characterised by irregularly formed letters, or inability to write straight on a blank paper with no guideline. Some studies have also reported gross motor difficulties in dyslexia, including motor skills disorder. This difficulty is indicated by clumsiness and poor coordination. The relationship between motor skills and reading difficulties is poorly understood but could be linked to the role of the cerebellum and inner ear in the development of reading and motor abilities.
Mathematical abilities
Dyslexia and dyscalculia are two learning disorders with different cognitive profiles. Dyslexia and dyscalculia have separable cognitive profiles, mainly a phonological deficit in the case of dyslexia and a deficient number module in the case of dyscalculia. Individuals with dyslexia can be gifted in mathematics while having poor reading skills. They might have difficulty with word processing problems.
Adaptive attributes
A study has found that entrepreneurs are five times more likely to be dyslexic than average citizens. Evidence based on randomly selected populations of children indicate that dyslexia affects boys and girls equally; that dyslexia is diagnosed more frequently in boys appears to be the result of sampling bias in school-identified sample populations. In the United States, researchers estimate the prevalence of dyslexia to range from three to ten percent of school-aged children though some have put the figure as high as 17 percent. Recent studies indicate that dyslexia is particularly prevalent among small business owners, with roughly 20 to 35 percent of US and British entrepreneurs being affected.
