In reading, psychologist called transforming written word to a spoken word as reading aloud. Here, we need two routes to convert a written word to a spoken word. It can also be called dual route theory. This theory involves mental lexicon and non-lexical procedure.
Mental lexicon is used for recognizing familiar words because those words are stored mentally in our lexicon. It has three kinds of information about words. Those are spelling, pronunciation and meaning. In reading, we need the mental lexicon to comprehend the word. This is called visual word recognition which consists of locating a familiar printed word in one’s mental lexicon. It makes the reader be able to recognize and read the word aloud. It is because part of word’s representation in the mental lexicon is a specification of how it is pronounced. This reading aloud is called lexical procedure for reading aloud.
The other is non-lexical procedure which enables a person to translate an unfamiliar word into a spoken word. There is no representation of unfamiliar word in mental lexicon. When we read some text, we may find unfamiliar word that will not be present in our mental lexicon. If the unfamiliar word comes repeatedly, the strategy we use is pronouncing the word and store in the memory. So, if we find the same word we will remember the word. We pronounce the unfamiliar word because we can remember the sound easier than the letter because our visual memories have lower capacities than our phonological memories.
The procedure of translating an unfamiliar written word to a spoken word is called non-lexical procedure for reading aloud. These two routes are important to convert a written word to spoken word because we need mental lexicon for familiar words so that we can understand the text. In addition, we should have non-lexical procedure because we will find difficulty to go further with the text if there are some unfamiliar words if we do not translate the written word into a spoken word.
However, this procedure is wrong according to neuropsychological research with brain damaged people so that there is elaboration of dual route theory. According to them, there are three kinds of information about words which are stored separately. Those are orthographic lexicon which is the spelling of a word, phonological lexicon which represents pronunciation of a word and semantic system which is about the meaning of a word. This theory involves two routes. One route consists of orthographic lexicon, semantic system and phonological system and the other route consists of grapheme-phoneme correspondence rule. The difference of this theory is that regular words can be read correctly by lexical and non lexical reading route while irregular words can only be read by the lexical reading route. Moreover, the research find that brain damaged people any two of the system is still intact while the third is damaged. For example, a person with dementia, only the semantic system is damaged. A person with anomia will get damaged in terms of pronunciation and a person with surface dyslexia, only the orthographic lexicon is affected. This theory allows how to see different kind of impairment because it broke up the mental lexicon into three separate systems.