ACQ Vol 13 no 2 2011

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Assessment
ACQ Volume 13, Number 2 2011 79
Kristy Jones
(top), Anne
Castles (centre),
and Saskia
Kohnen
This article
has been
peer-
reviewed
Keywords
DUAL ROUTE
MODEL
DYSLEXIA
READING
DISORDERS
TREATMENT
it should be emphasised that we see these subtypes, not
as distinct subgroups that are qualitatively different from
normal readers, but as subgroups at the extreme ends of a
continuum of performance on a particular subskill.
Before we describe the different subtypes of reading
disorders, we will outline the set of processing abilities
children need to acquire, to become proficient readers. In
order to conceptualise the complex cognitive processes
involved in reading, we rely on dual route theory (e.g.,
Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001;
Friedmann et al., in press; Jackson & Coltheart, 2001; see
Figure 1). Although there are other models of the reading
process (e.g., Plaut, McClelland, Seidenberg, & Patterson,
1996), the modular nature of the dual route model makes
it particularly suitable for identifying and accounting for
different types of reading disorders: it is possible to easily
and clearly identify the different processes that need to
be acquired for skilled reading and to develop specific
tests to assess the functioning of those processes.
Such assessment aids clinicians in developing a focused
treatment approach.
According to the dual route theory, various processing
steps take place from first seeing a written word to
subsequently reading it aloud and/or comprehending
its meaning. As illustrated in Figure 1, the initial set of
processes is summarised as visual orthographic analysis .
There are three functions within visual orthographic
analysis. First, letter identification takes place. This
involves recognising what is seen as a series of letters,
not numbers or symbols. Second, letter position within a
word is encoded (so that words like sliver and silver can
be distinguished from each other). Last, when more than a
single word is being read, letter-word binding occurs, such
that the letters of each word are correctly associated with
the word they appear in, and not another one (Friedmann et
al., in press). For example, in order to read the two words
tall walk correctly, the letters T A L L need to be associated
with the first word and the letters W A L K with the second
word. If the association process goes wrong, a reading
error such as wall talk may occur.
The word is then further processed via two different
routes. The type of word that is read predicts which route
will be successful in producing the correct response.
Regular words (e.g., cat, hut, pet) and words (or nonwords)
that a child has never come across before can be sounded
out phonetically via the letter-sound-correspondences,
along the so-called nonlexical route (Coltheart et al.,
2001). However, for irregular words (e.g., friend, yacht),
This paper presents an overview of several
subtypes of developmental reading disorders
including phonological dyslexia, surface
dyslexia, hyperlexia, poor comprehenders,
and the less-recognised subtypes of letter-
position dyslexia and attentional dyslexia.
Although clinicians may be familiar with the
symptoms of phonological and surface
dyslexia, the symptoms of the other reading
disorders noted may be less familiar and
therefore methods of assessment and
directions for treatment may be unclear. Each
subtype is described and accounted for in the
context of the dual route theory of reading.
Current research on remediation strategies is
also surveyed, providing a basis for developing
treatment programs for both pure and
complex developmental reading disorders.
Although most clinicians are familiar with terms
such as “specific reading disorder” or “dyslexia”,
the different kinds, or subtypes, of developmental
reading disorders that can affect children may not be as
widely known. This is particularly true for some of the
subtypes that have only recently become the focus of
research attention. In this article, we outline the symptoms
that characterise six specific subtypes of reading disorders
and provide suggestions for diagnosis and treatment,
based on theoretically driven research.
It is unusual for a child to suffer from just one subtype of
reading disorder. Although pure cases do exist (e.g., Broom
& Doctor 1995a; Castles & Coltheart, 1996; Friedmann,
Kerbel, & Shvimer, in press; Friedmann & Rahamim, 2007;
Rowse & Wilshire, 2007), in most cases children with
a developmental reading disorder will show symptoms
associated with more than one subtype (e.g., Brunsdon,
Hannan, Coltheart, & Nickels, 2002a). It should also be
acknowledged that although some of the subtypes we
discuss, e.g., phonological and surface dyslexia, are well-
known and have been thoroughly researched in terms of
causal links and treatment, other subtypes, e.g., letter-
position dyslexia and attentional dyslexia, are still relatively
new, with research being in its infancy. Appropriate caution
should therefore be exercised in relation to decisions about
assessment and treatment in the latter instances. Finally,
Subtypes of
developmental reading
disorders
Recent developments and directions for treatment
Kristy Jones, Anne Castles, and Saskia Kohnen