A thesis submitted in partial fulfilment of - Queen Margaret University

thousand words according to Levelt et al. (1999). Word form errors are also
often produced by people with aphasia but on a more regular basis often
affecting the communication of their message. Similar to healthy adults word
form errors have similar phonetic characteristics to the target word. Such errors
are phonotactically legal in that they do not contain sequences that are not
found in their native language (Nickels, 2001).
2.8.2 Conceptual meaning of words
The representation of the meaning of a word is held in the semantic system. It is
generally agreed that the semantic system contains all of our concepts,
meanings, images and the associations we have linked to them (Robertson,
1999). New information is encoded into our memory by describing it in terms of
what is already known and its semantic relations to already held representations
(Bjork and Bjork, 1996). Just as the lexicon is the mental dictionary the semantic
system is our mental encyclopaedia where we tend to categorise knowledge and
concepts (Daniele, Giustolisi, Silveri, Colosimo and Gainotti, 1994) by for
example, perceptual (shared function – for example, sofa and chair) or biological
features (for example, fruit or vegetables) (Harley, 2001). There is also
evidence for hierarchical relations between categories for example, a basic level
(cat), a superordinate level (mammal) and a subordinate level (Persian). The
semantic system also contains associations between words that regularly occur
together (for example, bread and jam), words with similar meanings (for
example, yacht and ship) as well as connotations relating to the words (for
example, a cat can be cuddly or scary) (Harley, 2001). Research has provided
evidence that the meaning of a word can be dissociated from the word form
therefore a word can be spoken or read without knowing its meaning (Ellis and
Young, 1996; Kay et al., 1992). However the naming of an object or picture
without semantics is not possible, therefore one can only name an object when
the semantic information attributed to that object is available (Hodges and
Greene, 1998). Studies have provided evidence for loss of semantic information
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