research, eye movement and visual processing factors are considered as key indicators of

reading difficulties. Therefore, these four individual predictors are discussed further in

this section.

Linguistic Predictors

 Among various linguistic indicators, the two most frequently identified factors that

are significantly correlated to later reading ability are phonological awareness and rapid-

naming deficit. During the last 25 years, research has provided a greater understanding

that phonological awareness is a foundation of reading acquisition. As a consequence, an

assessment of phonological awareness skills always has been included in early

identification of RD. Along with phonological awareness, a wider variety of recent

studies has highlighted rapid-naming skills as being highly correlated with their later

reading abilities (e.g., Wolf, 1999; Wolf & Bowers, 1999). Therefore, the following

section provides a neutral overview of the two skills and evidence of empirical studies as

key linguistic predictors of RD.

Phonological awareness

 In the 1970s, Isabelle Liberman and Donald Shankweiler introduced the significant

concept of phonological awareness to the field of reading (Liberman, 1973; Liberman et

al., 1974). They argued that an alphabetic system requires that readers have awareness

that words are made up of individual speech sounds (i.e., phonemes). Hence, if a child is

not sufficiently aware of the speech segments in spoken words, the child may have

difficulties in reading. These researchers and their colleagues studied young children and

poor readers and confirmed that they were lacking in awareness of the sound structure of

words (Liberman et al., 1974); that is, the children had difficulties performing activities

that require one to reflect on the speech sounds in words (e.g., counting the number of