Evidence that phonological mediation is not obligatory
The simple model showed that there is a route from written familiar words to meanings which does not involve the pronunciations of the words. However, one may argue that there may be a different situation in brain-damaged people. Evidence from both normal and brain-damaged (e.g. dyslexia caused by brain damages) people supported the theory that human can retrieve meaning of word from its printed form regardless of the pronunciation.
Studies with normal readers
Kleiman (1975) carried out three experiments to investigate whether or not recoding of speech occurs during reading before or after lexical access. Those tests established the effects of a concurrent repetition of rapidly spoken words (shadowing) task on lexical information retrieval. It was found that speech recoding occurs after lexical access, which means that speech recoding is not necessary for normal readers in getting the semantics of words. Nevertheless, it is worth noting that although the phonological mediation in word recognition is not obligatory, readers still concern phonological information as a part of the recognition process. The involvement of phonological mediation however might mislead the recognition of words. Van Orden (1987) found that when normal readers were asked to respond as quickly as they can, errors are made in questions such as: whether a “rows” is a “flower”.
Study with brain-damaged readers
Report by Richard and Vincent (1997) on the case of patient PS who suffered from dyslexia after an acute infarct, indicated that some brain damaged patients showed a good understanding on meanings of words; however produced a number of errors in tests of oral reading, picture naming, etc. In the case of PS, tests were carried out to investigate his performances on word recognition task. His results showed that he had no problem on getting the meaning from print while cannot pronoun those word; he even always gave definitions of the words which were mispronounced. It again supported the theory that people can regain semantics from prints without the access of phonology.
From orthography to phonology
The issue about routes involved in retrieval of phonology from orthography can be
explained by citing the Dual-Route Cascaded (DRC) Model (Jackson & Coltheart, 2001; Clotheart, 2006). Together with evidence on both normal and brain-damaged readers’ performance on word recognition, this section is to discuss the three routes which are believed to involve in retrieving phonology from orthography.
Dual-Route Cascaded (DRC) Model
The Dual-Route Cascaded (DRC) Model, which was introduced by Jackson and Coltheart in 2001, was a computational model that computed pronunciation from print via three routes: semantic lexical route, non-semantic lexical route and non-lexical Grapheme-Phoneme Conversion (GPC) route. (See Fig. 2).
Fig. 2. The DRC model of visual word recognition. (Jackson et al., 2001; Clotheart, 2006)
According to this model, the semantic lexical route contains three main mechanisms: the semantic system, the orthographic input lexicon, and the phonological output lexicon. This route suggested that we retrieve pronunciation of words by identifying their orthography and meanings, thus the words should be real and familiar in order to b e efficiently looked up in the mental lexicon, which contains knowledge about existing words that we have experienced. The non-semantic lexical route is similar to the semantic lexical route, but it gets from print to speech without via semantics and is believed that unfamiliar words can be processed here. In the contrast, reading via the non-lexical GPC route is not referencing the lexicon in any ways, so unfamiliar, irregular or even non-words, which are meaningless since they do not exist, could still be pronounced via this route.
Evidence that support the DRC Model
The DRC Model was found to be the most successful model in explaining the word
recognition in reading aloud. Evidence on the performance on word recognition in reading of normal and brain-damaged readers is to be discussed to support the DRC Model.
Study with normal readers
It was introduced that different kinds of words are processed in different routes and there are mainly two ways to categorize words: regularity and frequency. For instance, regular words are BED, REST, BIRD and irregular (exception) words are ISLAND, ONCE; high-frequency words include EAT, BED, GOOD and low-frequency words include DIGNITY, CHAOS. Seidenberg and his colleagues in 1984 suggested that regularity and frequency of words are major factors in word recognition. They carried out a study on normal readers which aimed to investigate the effect of the regularity-frequency interaction on word recognition by measuring the reaction time. The results are shown in Fig. 3.
Fig. 3. Regularity X frequency interaction. (Seidenberg et al. 1984)
It was reported that there was a marked difference when comparing the reaction time for low frequency regular words to low frequency irregular words, but less difference for high frequency words. Their findings supported the theory that word recognition involves different routes, and each of these routes processes specific type of words (e.g. the semantic lexical route processes high frequency regular words).
Morton (1964b) asked skilled readers to read aloud some articles, and errors were found that word was replaced by another word of similar meaning when the readers were reading aloud: for example, misreading might as "may". It shows that people understand the meaning of the words prior to the pronunciation state. This finding supported the semantic route of the DRC model.
Studies with brain damaged readers
Cases on different kinds of dyslexia were reviewed and discussed in this section,
including surface (or grapheme-phoneme conversion) dyslexia, of which patients may find it
difficult to pronounce irregular words, they may respond "iz-land" when shown the word
"island"; and deep (or semantic) dyslexia, of which patients make errors in semantic
relationship of words, for example, they may read the word “hen” in responding to "egg".
Linguistic studies of six cases of dyslexia are presented in the paper by Marshall and
Newcombe (1973). One of the six cases was the study about patient JC; JC was a 45-year-old
man, who had suffered from surface dyslexia. His word recognition performance showed that
he had no problem with the semantic route but the mistakes he made were described as
partial failures of grapheme-phoneme conversion. Here in this case, semantic lexical route
and non-lexical GPC route were identified. Another case in the same paper was about patient
KU, who was a 49-year-old man suffered from deep dyslexia. Semantic errors were observed
in his reading such as saying “diamond” when saw the word “necklace”. Moreover, it was
found that KU was unlikely to read a word correctly without knowing its meaning. This study
was relevant in talking about the role of the semantic routes.
Michel, Henaff and Intrilligator (1996) reported the case of a 23-year-old man who had
deep dyslexia after brain surgery. His reading abilities dropped: semantic errors were found,
non-word reading was impossible, etc. This old man were said to be impaired in the semantic
routes and non-lexical GPC route.
All these cases showed that there are totally three routes in word recognising task: the
semantic lexical route, non-semantic lexical route and the non-lexical grapheme-phoneme
conversion routes.
Conclusion
The title of this paper invites review and reference to current evidence on the
performance of normal and brain-damaged readers on word recognition; and to answer the
questions about how people get from print to meaning and pronunciation. By citing relevant
research and case studies, and comprehending the concepts of route-models, the two
questions raised can be answered.
Studies with normal (Kleiman, 1975) and brain-damaged (Richard et al., 1997) people
found that phonological mediation is not obligatory. Given that although brain-damaged
people could not pronounce some words, they still could explain the meanings of the words.
It was also pointed out by Van Orden in 1987 that phonological mediation is not necessary,
yet normal readers take it into account when they are doing word recognition tasks. However
the involvement of phonological mediation sometimes misleads recognition of words.
The Dual-Route Cascaded (DRC) model (Jackson et al., 2001; Coltheart, 2006) suggested
that three pathways are involved in word recognition: semantic lexical route, non-semantic
lexical route and non-lexical Grapheme-Phoneme Conversion (GPC) route. Research and
case studies on both normal (Seidenberg et al., 1984) and brain-damaged (Marshall et al.,
1973; Michel et al., 1996) people gave evidence to the theory that there are three routes in the
process of word recognition.
Importantly though, reading and word recognition are very complicated mechanism and
there will never be too many clarifications. Our knowledge in this field has been improved by
previous studies; however further research is essential so as to provide more evidence on how
people get from orthography to semantics and phonology.
References
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