Dual-route hypothesis to reading aloud

Lexical route The lexical route is the process whereby skilled readers can recognize known words by sight alone, through a "dictionary" lookup procedure. According to this model, every word a reader has learned is represented in a mental database of words and their pronunciations that resembles a dictionary, or internal lexicon. The internal lexicon encompasses every learned word, even exception words like 'colonel' or 'pint' that don't follow letter-to-sound rules. This route doesn't enable reading of nonwords (e.g. 'zuce'), though some phonological output can still be produced by matching the word to an approximation in the lexicon (e.g. 'sare' activating visually similar known words like 'care' or 'sore'). ==Transparency of phonological rules==

According to research, the amount of time required to master reading depends on the language's adherence to phonological rules. A written language is described as transparent when it strongly adheres to spelling-sound rules and contains few exception words. Because of this, the English language (low transparency) is considered less transparent than French (medium transparency) and Spanish (high transparency) which contain more consistent grapheme-phoneme mappings. This difference explains why it takes more time for children to learn to read English, due to its frequent irregular orthography, compared to French and Spanish. The Spanish language's reliance on phonological rules can account for the fact that Spanish-speaking children exhibit a higher level of performance in nonword reading, compared to English and French-speaking children. Similarly, Spanish surface dyslexics exhibit less impairment in reading overall, because they can rely upon consistent pronunciation rules instead of processing many exception words as a whole in the internal lexicon. The dual-route system thus provides an explanation for the differences in reading acquisition rates as well as dyslexia rates between different languages. ==Reading speed==

Skilled readers demonstrate longer reaction times when reading aloud irregular words that do not follow spelling-sound rules compared with regular words. When an irregular word is presented, both the lexical and nonlexical pathways are activated but they generate conflicting information that takes time to be resolved. The decision-making process that appears to take place indicates that the two routes are not entirely independent from one another. This data further explains why regular words, that both follow spelling-sound rules and have been stored in long-term memory, are read faster since both pathways "agree" about the issue of pronunciation. ==Attentional demands of each route==

According to the current model of dual-route processing, each of the two pathways consumes different amounts of limited attentional resources. ==Reading disorders==

The dual-route hypothesis to reading can help explain patterns of data connected to certain types of disordered reading, both developmental and acquired. Children with reading disorders rely primarily on the sub-lexical route while reading. Research shows that children can decode non-words, letter by letter, accurately but with slow speed. However, in decision tasks, they have trouble differentiating between words and pseudohomophones (non words that sound like real words but are incorrectly spelled), thereby showing that they had impaired internal lexicons. Words like "state", and "abdominal", are examples of words that people with surface dyslexia will not have a problem pronouncing, as they do follow proscribed pronunciation rules. Surface dyslexics will read some irregular words correctly if they are high frequency words such as "have" and "some". Acquired phonological dyslexia Acquired phonological dyslexia is a type of dyslexia that results in an inability to read nonwords aloud and to identify the sounds of single letters. However, patients with this disability can holistically read and correctly pronounce words, regardless of length, meaning, or how common they are, as long as they are stored in memory. This type of dyslexia is thought to be caused by damage in the nonlexical route, while the lexical route, that allows reading familiar words, remains intact. ==Computational modeling of the dual-route process==

A computational model of a cognitive task is essentially a computer program that aims to mimic human cognitive processing. This type of model helps bring out the precise parts of a theory and disregards the ambiguous sections, as only the clearly understood parts of the theory can be converted into a computer program. The ultimate goal of a computational model is to resemble human behavior as closely as possible, such that factors affecting the functioning of the program would similarly affect human behavior and vice versa. Reading is an area that has been extensively studied via the computational model system. The dual-route cascaded model (DRC) was developed to understand the dual-route to reading in humans. Some commonalities between human reading and the DRC model are: • Frequently occurring words are read aloud faster than non-frequently occurring words. • Actual words are read faster than non-words. • Standard sounding words are read aloud faster than irregular sounding words. The DRC model has been useful as it was also made to mimic dyslexia. Surface dyslexia was imitated by damaging the orthographic lexicon so that the program made more errors on irregular words than on regular or non-words, just as is observed in surface dyslexia. Phonological dyslexia was similarly modeled by selectively damaging the non-lexical route thereby causing the program to mispronounce non words. As with any model, the DRC model has some limitations and a newer version is currently being developed. ==References==