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The Relationship Between EarlyLanguage Delay and Later Difficulties inLiteracyRhona Larney aa West Dunbartonshire Psychological Service , Dunbarton, G82 3JL,ScotlandPublished online: 17 Sep 2010.

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Early Child Development and Care, 2002, Vol. 172(2), pp. 183–193

The Relationship Between Early LanguageDelay and Later Difficulties in Literacy

RHONA LARNEY

West Dunbartonshire Psychological Service, Dunbarton G82 3JL, Scotland

(Received 20 September 2001)

The relationship between early language delay and later literacy development is explored. The paperbegins by considering a diagnostic model of early language delay, upon which subsequent definitionsof language delay are based. The degree to which there is continuity between early language delay andlater difficulties in literacy development is then explored. The findings of four longitudinal studies areconsidered in turn, and the degree to which they show evidence of continuity between early languagedelay and later literacy difficulties is evaluated. From these four studies, the author identifies twosignificant findings: (a) there is strong evidence of continuity between early language delay and laterreading difficulties for all children with early language delay, although some of these readingdifficulties may be residual and mild; and (b) the likelihood that children with early language delaywill develop later difficulties in literacy depends largely on the age to which language impairmentpersists and the severity of the impairment. The author concludes that language delay in the earlyyears is a key risk factor for later literacy difficulties. Implications for future research and practice areidentified and discussed.

Key words: language delay, early years, literacy, expressive, receptive

INTRODUCTION – LANGUAGE ACQUISITION IN THE EARLY YEARS

Competency in spoken language is a skill which is acquired easily by the majority of children

within the first five years of life. Indeed, the ease with which language is acquired by most

children has led many researchers to subscribe to the Chomskyan notion that human infants

are uniquely predisposed to learn language (Ward, 1999). Nonetheless, in spite of this natural

predisposition to learn language, there is a relatively stable subset of children for whom

language acquisition is significantly delayed during the early years of life. Delay in language

development among such children has been found to be the most common single difficulty in

the preschool years (Lees and Urwin, 1997).

While the key characteristic of children with early language delay is difficulty in language

and communication, there is accumulating evidence that this subgroup of children are also at

risk for developing later difficulties in a range of additional areas, including cognitive,

academic, behavioural, and social domains (Aram et al., 1984; Aram and Nation, 1980;

Johnson et al., 1999; Lewis et al., 2000; Ward, 1999).

* E-mail: rlarney@hotmail.com

ISSN 0300-4430 print; ISSN 1476-8275 online # 2002 Taylor & Francis LtdDOI: 10.1080=03004430290013335

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EARLY LANGUAGE DELAY AND LATER LITERACY DEVELOPMENT – IS THEREA LINK?

One key area which is thought to be adversely affected by language delay in the early years is

that of literacy development. At first glance, it would seem clear that children who are de-

layed in their language development in the early years would proceed to experience diffi-

culties in reading in later years, since many researchers have found that competence in

language is strongly related to proficient reading development (e.g., Butler, 1999). However,

on the whole, research findings on the level of continuity between early language delay and

later literacy difficulties indicate that the relationship between the two is not quite as

straightforward as one might expect.

In this paper, the author attempts to draw on the key research findings in the field to clarify

whether there is continuity between language delay in the early years and subsequent pro-

blems in literacy. Section One begins by exploring the nature of language delay under the

broad headings of diagnostic classification and prevalence. Section Two critically evaluates

the findings of some of the most significant research studies which examine the relationship

between language delay and later difficulties in reading. Section Three reflects on the key

findings arising from research on this area, as well as on some implications of these findings.

Finally, Section Four considers the major implications for future research arising from the

evidence presented.

LANGUAGE DELAY: DIAGNOSTIC CLASSIFICATION AND PREVALENCE

Language delay is a heterogeneous condition. Difficulties arise when this factor of hetero-

geneity is not accounted for in research studies, leading to potential misinterpretations of the

link between language delay and later literacy development. To clarify the heterogeneous

nature of the condition, the nature of language delay is explored here, using Whitehurst and

Fischel’s (1994) diagnostic model of language delay.

Diagnostic Classification – Whitehurst and Fischel’s (1994) Model

1 Specific vs. Secondary Language Delay

Whitehurst and Fischel (op cit.) begin by distinguishing between specific and secondary

language delay. Specific language delay (also known as primary language delay – Law

et al., 2000; and specific language impairment – e.g., Bishop, 1992) refers to a delay in

language development, usually without a clear etiology, in the presence of normal non-

linguistic cognitive and physical abilities (Law et al., 1998; Whitehurst and Fischel, op cit.).

Secondary language delay, in contrast, refers to a delay in language development, usually as

a result of a known etiology, which is secondary to other conditions (e.g., mental retardation,

physical handicap, hearing loss, brain damage, environmental deprivation, and pervasive

developmental disorder or autistic spectrum disorder) (Law et al., 1998; Whitehurst and

Fischel, op cit.). Whitehurst and Fischel (op cit.) emphasise the importance of making this

distinction between specific and secondary language delays in drawing conclusions from

research findings, as each has a different prognosis and therefore a different impact on later

literacy development.

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2 Expressive Delay vs. Receptive-Expressive Delay

Within the subtype of specific language delay, Whitehurst and Fischel (op cit.) distinguish

between children with specific expressive language delay (i.e., difficulties in producing

language) and those with specific receptive-expressive language delay (i.e., difficulties in

understanding language). Children who have receptive delays but with no difficulties in

expression are very rare, and have not been afforded a separate diagnostic label under

Whitehurst and Fischel’s (op cit.) model.

It is important to point out that the term specific expressive language delay is synonymous

with expressive type specific language impairment (SLI-E), a term preferred by Rescorla

(e.g., Rescorla et al., 1997), and also with slow expressive language development (SELD), a

term preferred by Paul (e.g., Paul and Fountain, 1999).

3 Components of Language

Finally, Whitehurst and Fischel (op cit.) refer to four key components of language which can

be affected by delays in expressive or receptive language functioning. First, difficulties in

phonology affect articulation and/or awareness of the phonological features of words. Second,

difficulties in semantics affect the understanding of meanings associated with words. Third,

difficulties in syntax affect the ability to organise words into meaningful sentences in a

grammatically correct way. Fourth and finally, difficulties in pragmatics affect the ability to

construct and interpret messages in a way that meaning is communicated from one person to

another. Depending on which language component(s) is affected by the delay, a different

prognosis will emerge (Whitehurst and Fischel, op cit.), and therefore a different outcome for

literacy development will present.

Prevalence of Early Language Delay

Estimates of the prevalence of language delay vary depending on the age of the child, the

criteria used to define delay, whether specific and secondary language delay are identified, the

cut-off scores used for classification, the measurement techniques used, and where the survey

is carried out (Law et al., 1998) (e.g., Stevenson and Richman, 1976, cite a rate of 3–4%

among their sample of 3-year-olds in London; Silva, 1980, cites a rate of 8% among his

sample of 937 3-year-old children in New Zealand). In a systematic review of the literature,

Law et al. (1998; 2000) obtained 16 prevalence estimates of primary/specific speech and

language delays from 21 publications, and arrived at an overall median prevalence rate of

5.95%. They conclude that speech and language delay is a common problem which can have

important implications for the child.

CONTINUITY BETWEEN EARLY LANGUAGE DELAY AND SUBSEQUENTPROBLEMS IN LITERACY: EVIDENCE FOR AND AGAINST

There is a range of studies which have examined the question of continuity between

language delay in the early years and later problems in literacy. A carefully-selected subset

of these is explored here. The studies selected for exploration are longitudinal and pro-

spective in nature, since these are the most useful in drawing conclusions about the degree

of continuity between early language delay and school-age literacy difficulties. Four studies

are reviewed in detail here, referred to in turn as: (i) the English studies (Bishop and

Adams, 1990; Bishop and Edmundson, 1987; Stothard et al., 1998); (ii) the Portland

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studies (Paul, 1991; Paul et al., 1996; Paul et al., 1997); (iii) the Ohio studies (Lewis et al.,

2000); and (iv) the Ontario studies (Johnson et al., 1999).

1 The English Studies (Bishop and Adams, 1990; Bishop and Edmundson, 1987;Stothard, Snowling, Bishop, Chipchase and Kaplan, 1998)

To date, Dorothy Bishop’s research on the relationship between early language delay and

later literacy development has involved a twelve-year longitudinal investigation of children

who were identified with a preschool language impairment (Bishop and Adams, 1990;

Bishop and Edmundson, 1987; Stothard et al., 1998). Children were initially recruited for

the study via speech-language pathologists and paediatricians in the northeast and north-

west of England who were asked to refer any child aged between 3;9 and 4;2 who was

being seen because of concern about language development, excluding those whose lan-

guage difficulties were due to secondary conditions (Bishop and Edmundson, 1987). The

language-impaired children (n¼ 87) were assessed using a battery of both standardised and

functional language measures which looked at expressive phonology (percentage con-

sonants correct – PCC), syntax and morphology (MLU; Action Picture Grammar score),

semantic relationships and vocabulary (Bus Story Information score; Action Picture

Information score; BAS – Naming Vocabulary), receptive ability to handle grammar

and vocabulary, and a general measure of verbal comprehension of instructions (BAS –

Verbal Comprehension; BPVS). Nonverbal IQ was also assessed using the Leiter

International Performance Scale. Sample children were tested at ages 4, 4;6 and 5;6. At

each stage, scores were compared to that of controls (37 4-year-olds; 23 412-year-olds; and

19 512-year-olds).

Although Bishop and Edmundson (op cit.) had aimed to exclude children with secondary

language delay (General Delay – GD group), 19 of the children in the sample scored more

than two SDs below the mean on the Leiter test. Data from the GD group (n¼ 19) were

considered separately from those of the SLI (Specific Language Impairment) group (n¼ 68).

Results showed that in 44% of the SLI cases (n¼ 30), the language delay had resolved by the

age of 5;6 (the ‘good outcome’ group). In contrast, only 11% of the GD cases (n¼ 2) had a

comparatively good outcome.

The following key conclusions were drawn from their findings: (a) severity and persistence

of language delay were directly related to the number of language functions impaired (i.e.,

impairments in phonology only had a good outcome, while impairments in phonology, se-

mantics, and syntax had a poorer outcome); (b) non-verbal IQ within the normal range (i.e.

SLI cases) had a significantly positive effect on outcome; and (c) age had a significant effect

on outcome (i.e., if impairments were still present at age 5 and beyond, the likelihood of

remission was poor).

Bishop and Adams (1990) followed up this sample at age 8;6 to determine the effects

which earlier language delay had on the children’s literacy development. A total of 83

children were assessed and compared to a control of 30 8-year-olds. Of the 29 children with

good outcome at 5 years, 28 were normal readers at age 8;6. This contrasts with 28 out of 37

cases with poor outcome at 5 years becoming normal readers, and only 9 out of 16 cases of

general delay.

Bishop and Adams (op cit.) concluded that: (a) provided that language delay has re-

solved by age 5;6 literacy development is normal; (b) children with persisting language

delay at age 5;6 are likely to have reading difficulties, mostly in the area of reading

comprehension rather than word decoding; (c) isolated phonological problems in pre-

literate children are not predictive of reading difficulties, while difficulties in syntactic and

semantic ability are predictive; and (d) MLU at age 4;6 is the strongest predictor of

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subsequent reading ability at 8;6. Overall, Bishop and Adams (op cit.) provided early

evidence that children with preschool language delay are at risk of difficulties in literacy

development at early school-age.

A follow-up of this sample into adolescence was carried out recently (Stothard et al.,

1998). At age 15–16 years, 71 of the original sample were compared with age-matched

normal-language controls on a battery of tests of spoken language and literacy skills. It was

found that outcome at age 15/16 years was strongly associated with language skills at age

5;6. First, the resolved SLI group identified at age 5;6 was indistinguishable from controls on

some measures (e.g., tests of vocabulary and language comprehension), but showed sig-

nificant deficits on tests of phonological processing and literacy skill (e.g., Sentence Re-

petition task; Nonword Repetition). While this group were at a lower risk for reading and

spelling difficulties than children from the persistent SLI group or the GD group, difficulties

still emerged in the resolved SLI group, lending support to the hypothesis of ‘illusory re-

covery’ (Scarborough and Dobrich, 1990), i.e., children whose language difficulties resolve

early (e.g., at age 5) have residual, but mild, processing impairments that place them at risk

for later failure. If such a period of illusory recovery is protracted, this would explain why

difficulties in literacy at age 15/16 years were not detected among the resolved SLI group at

age 8;6 in the earlier Bishop and Adams study (op cit.). Second, among the persistent SLI and

GD groups, the reading and spelling difficulties evident at age 8;6 were still present at age

15/16, and the adolescents’ literacy skills were broadly consistent with their more general

verbal difficulties (Stothard et al., op cit.).

Stothard et al. (op cit.) concluded by outlining a model of risk for developing literacy

difficulties following preschool language delay: (a) at age 5;6 children with persistent SLI or

General Delay are at high risk of language, literacy and educational difficulties throughout

childhood and adolescence; (b) at age 5;6 children with resolved SLI make relatively normal

progress in spoken language development but have weaker literacy skills relative to their peer

group. According to Stothard et al. (op cit.), then, there is continuity between early language

delay and later literacy difficulties for all children who develop language delay in the early

years (whether it resolves by age 5 or not), but continuity increases significantly with greater

severity and persistence of the language impairment (i.e., higher risks for children with

persistent SLI and General Delay).

In spite of these unequivocal findings, it must be pointed out that there are a number of

methodological weaknesses evident in the Bishop studies. First, the control groups were not

studied longitudinally, which weakens any comparisons made between the control groups

and the language-impaired group. Second, the study did not begin assessing children until

age 4, by which time language impairment is much more likely to be severe and persistent. If

the study had begun to assess children from age 2 or 3, it is likely that more favourable

outcomes would have emerged. Studies throughout the 1990s (e.g., Rescorla and Schwartz,

1990; Paul et al., 1996) have begun to take account of the effect that ‘age to which im-

pairment persists’ can have on outcome by focusing on children from the age of 2.

2 The Oregon Studies (Paul, 1991; Paul, Hernandez, Taylor andJohnson, 1996; Paul, Murray, Clancy and Andrews, 1997)

In the Portland Language Development Project (PLDP), a five-year longitudinal study,

Rhea Paul followed children between 18 and 34 months of age with slow expressive

language development (SELD), and compared them with a group of normally speaking

children (Paul, 1991; Paul et al., 1996; Paul et al.,1997). Children were recruited for the

study through paediatricians’ offices, radio announcements and newspaper advertisements

requesting participation of families of 2-year-olds who did not talk. Thirty-two children

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with little speech were recruited at age 2, and remained in the study through to second

grade (age 7). SELD diagnosis was confirmed at intake through use of the Language

Development Survey (Rescorla, 1989), and the children were matched for SES and non-

verbal IQ to a control group (n¼ 27) of normal-language (NL) children for the entire

duration of the project.

Assessments of the SELD group at ages 3 and 4 revealed that their expressive voca-

bulary size moved within the normal range, but that more complex skills (e.g., sentence

structures and use of complex sentences, i.e., semantic and syntactic skills) remained de-

layed. Follow-ups of this sample at kindergarten, first grade, and second grade (ages 5, 6

and 7 respectively) aimed to look at the effects of earlier expressive language delay on

literacy skills, in particular higher-order literacy skills as these skills had not been the

focus of earlier studies (e.g., Bishop and Adams, op cit.). Skills which were examined

were: (a) narrative development (a strong predictor of school success, and related to

reading) (Paul et al., 1996); and (b) metaphonological performance (Paul et al., 1997)

(a skill also related to reading progress).

In their kindergarten year (age 5), children with SELD were subdivided into two groups:

those who had moved within the normal range of expressive language (n¼ 17) (History of

Expressive Language group, HELD) and those who continued to score below the normal

range in expressive language at school age (n¼ 10) (Expressive Language Delay group,

ELD). At ages 5, 6 and 7, the children were administered a narrative generation task. Nar-

ratives were analysed for MLU, lexical diversity, amount of information included, proportion

of complete cohesive ties, and overall stage of narrative maturity.

Different outcomes emerged for different groups. First, in the HELD group, while syn-

tactic deficits persisted to age 4, and narrative deficits to age 6, the long-term prognosis for

these children was good. Deficits in both syntax and narrative narrowed progressively and

appeared to resolve more or less completely (Paul et al., 1996). Second, in the ELD group,

deficits in syntax and narrative also narrowed towards second grade, such that performance in

this area was very similar to that of peers with normal language history. This group scored

within (though at the low end of) the normal range on standardised measures of language and

school achievement (Paul et al., 1996).

In a second study, Paul et al. (1997) focused on metaphonological skills, speech, language,

cognitive skills and reading achievement in second grade. Results showed that there were no

statistically significant differences between the HELD group and NL group in the areas most

closely related to literacy (reading recognition, reading comprehension, or spelling

achievement). Children in the HELD group performed within the normal range of school

achievement. Children in the ELD group performed at a lower level than children in either the

HELD or NL groups, but still within the normal range of school achievement for their age.

Paul et al. (1997) concluded by stating that SELD is not a significant risk for later reading

difficulties, but that it is probably too soon to rule out long-term risk entirely. They re-

commended longer-term follow-up into the intermediate and secondary grades (as Stothard

et al., 1998, have already done) to confirm whether or not these positive findings in the early

school years extend to later school years. As outlined earlier, however, age-appropriate de-

velopment in literacy in the early school years may not rule out the emergence of literacy

difficulties in later school years (e.g., Stothard et al., 1998), a factor which many researchers

have not yet explored (e.g., Paul et al., 1996; 1997).

Limitations of Paul’s longitudinal study must be pointed out at this stage. First, the number

of children who remained in the ELD group at follow-up was small (n¼ 10), making it

difficult to detect statistically significant differences between this group and the NL and

HELD groups. Second, all children in the study came from middle-class backgrounds, further

limiting generalisability of findings to the population at large. Finally, the study focused on

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children with expressive language difficulties only, thereby not allowing the possibility of

drawing conclusions relating to children with receptive difficulties, or to children with

secondary language delay.

3 The Ohio Studies (Lewis, Freebairn and Taylor, 2000)

The academic outcomes of 4–6 year-old preschool children (n¼ 52) with moderate to

severe speech sound (expressive phonology) disorders were the subject of a longitudinal

study carried out in Cleveland, Ohio (Lewis et al., 2000). The children were recruited from

the clinical caseloads of speech/language pathologists working at community speech and

hearing centres or in private practice in the greater Cleveland area.

The children were assessed at preschool age in the following areas: phonological pro-

cessing (Word Discrimination Subtest of the Test of Language Development, TOLD); pho-

nological encoding (Nonsense Word Repetition Test); phonological production (Khan-Lewis

Phonological Analysis, KLPA); semantic skills (Picture Vocabulary and Oral Vocabulary

subtests of TOLD); and syntactic skills (Grammatical Understanding, Sentence Imitation,

and Grammatical Completion Subtests of the TOLD). At school age, the participants were

examined on a test battery which included assessments of: reading decoding (Woodcock

Reading Mastery Tests, WRMT-R); reading comprehension (Reading Comprehension subtest

of the Wechsler Individual Achievement Test, WIAT); and spelling skills (Test of Written

Spelling-Third Edition, TWS-Z3).

Assessments at school-age (ages 8–11 years) revealed that 24 children were language-

impaired, 15 were reading-impaired, and 25 were spelling-impaired. On the basis of these

findings, the authors concluded that: (a) school-age children with histories of preschool

speech and language disorders are at high risk for reading, spelling and language problems

(consistent with the Bishop studies); (b) that risk of later reading difficulties rose when

children had preschool syntactic and semantic impairments as well as preschool phonolo-

gical impairments (consistent with the Bishop studies); (c) that family history for speech and

language disorders did not predict language, reading or spelling impairment at school age;

and (d) that family history for reading disorders was a good predictor of school-age reading

and spelling difficulties.

The findings of Lewis et al.’s (2000) study resonate quite strongly with those of Bishop, in

their conclusion that children with SELD are at risk of later reading difficulties. However,

their study must be criticised on two grounds. First, the sample selected for the study was a

clinical sample, and therefore likely to consist of the most severe cases of language im-

pairment and those with the poorest outcome. Second, the study did not have a control group

to enable comparisons to be made with children from the normal population.

4 The Ontario Studies (Johnson, Beitchman, Young, Escobar, Atkinson, Wilson,Brownslie, Douglas, Taback, Lam, and Wang, 1999)

A 14-year prospective, longitudinal study by Johnson et al. (1999) examined the speech and

language outcomes of a community sample of children with (n¼ 114) and without (n¼ 128)

speech and/or language impairments. Participants were initially identified at age 5 as part of a

3-stage epidemiological survey of all 5-year-old children in the Ottawa-Carleton region of

Ontario, Canada. The sample included children with both specific and secondary language

delay. Assessments were carried out at ages 5, 12 and 19 in the areas of speech and language,

demographic information, developmental/medical histories, cognitive and academic tests,

psychiatric measures, and parental marital and psychiatric questionnaires. Outcomes for the

sample at age 19 are described by Johnson et al. (1999).

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At age 19, there was a strong tendency for participants to retain their diagnostic classi-

fications from age 5. There were three outcome groups: normal speech and language

(n¼ 123); speech-only impairment (n¼ 42); and language impairment (n¼ 77; 42 without

and 35 with speech impairments). Performance of the 19-year-old participants on a test of

reading performance (Woodcock-Johnson Psychoeducational Battery-Revised, W-J Br.

Reading) revealed that participants from the normal speech and language group and from the

speech-impairment only group performed equally well. However, participants from the

language-impairment group performed at a significantly lower level than the other two

groups. On the basis of these findings, the authors concluded that: (a) children with early

language impairments show clear long-term deficits in language, cognitive and academic

domains compared to peers without early language difficulties; (b) children with secondary

language impairments had poorer long-term prognoses than those with specific language

impairments; and (c) children with speech impairments had better outcomes than those with

language impairments. These findings are highly consistent with those of Bishop, which is

the only other study reviewed here that, like Johnson et al. (op cit.), followed its sample

beyond the early school years (age 7/8).

Nonetheless, there are a number of methodological weaknesses in Johnson et al.’s (1999)

study. First, the authors employed a rather liberal cut-off point (1 SD below the mean) in

categorising children as language-impaired. Second, the age at which children first began

participating in the study was 5 years, increasing the chances that those children who were

language-impaired at this point were highly likely to have severe and persistent impairments

over the long-term. As pointed out earlier in relation to the Bishop studies, it is crucial that

longitudinal research begins to look at children with language impairments from the age of 2,

as this will provide information on children who spontaneously remit at age 3, at age 4 and at

age 5, as well as on those children whose impairments persist beyond age 5.

INTERPRETATION OF THE KEY FINDINGS

Although the four studies described here vary widely in several respects (e.g., their defi-

nitions of language delay; the ages at which they followed their samples; whether or not

they included children with secondary language delay, etc.), there are a number of key

findings which are common to most of the studies, and which are therefore likely to re-

present consistent patterns of outcome for children with language delay on which reliable

predictions may be based. It must be remembered, however, that interpretation of these key

findings should take account of the methodological limitations of the studies outlined

earlier.

First, strong evidence of continuity between preschool language delay and later literacy

difficulties was provided by the English studies and the Ontario studies, both of which

followed their samples over at least ten years. The Portland and Ohio studies provided

somewhat less evidence of continuity, but it must be remembered that these studies did not

follow their samples beyond age 8, and also focused on children with expressive delay only,

i.e., those children at least risk of later literacy difficulties. In the English and Ontario studies

which did follow children with expressive language delay beyond age 8, it was found that

such children did develop reading difficulties, although not to the same extent as children

with more severe and persistent language delays. On the basis of these findings, it seems that

there is indeed continuity between preschool language delay and later reading difficulties for

all children with early language delay.

Second, all four studies provided evidence that the likelihood that preschool children

with language delay will develop later difficulties in literacy depends largely on: (a) the

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age to which preschool language impairment persists; and (b) the severity of the im-

pairment. Preschool children who remain language-impaired by age 5 are significantly

more likely to remain language-impaired and to develop later literacy difficulties than

children whose early language delay resolves by age 3 or 4. However, as Stothard

et al. (1998) found, even those children whose early language delay resolves by age 5 are

still at some risk of later literacy difficulties, although not to the same extent as those with

persistent language impairment. The severity of the impairment also has a significant role

to play in determining outcome. Children who have impairment in a wider range of

language skills (e.g., expressive and receptive skills) are more likely to develop later

literacy difficulties than those with impairment in a narrow range of language skills

(expressive skills only).

Issues Arising From The Key Findings

There are three main issues arising from the findings presented in this review. First, natural

history data indicate that approximately 50–60% of children with specific expressive lan-

guage delay spontaneously remit by age 5 (Law et al., 2000), thereby being at a lower risk of

later literacy difficulties than the 50% who do not remit. While this is a highly promising

outcome for the former group, practitioners are still no more knowledgeable as to which

children will remit and which will not. Researchers have yet to identify consistent and re-

liable predictors of outcome for children with specific expressive language delay, and until

they identify such predictors, practitioners remain in the unenviable position of not knowing

whether to intervene in cases of early expressive language delay.

Second, the evidence indicates that there is continuity between early language delay and

later literacy difficulties. However, it is impossible to conclude definitively that this re-

lationship is causal. In fact, it is more likely that the relationship is correlational in nature,

with perhaps a common underlying cause which is responsible for both difficulties. It is

difficult, however, to identify any one cause which could be singularly responsible for all

variations of language delay and all variations of reading difficulty. Further research is ne-

cessary to clarify the precise nature of the relationship between language and literacy, and by

implication the relationship between language delay and literacy difficulties.

Third and finally, language delay in the preschool years may best be considered to be a

risk factor for later literacy difficulties. A child with preschool language delay is at risk of

later difficulties in reading, irrespective of which type of language delay is under con-

sideration. This should be the starting point of the practitioner’s (e.g., Speech and Lan-

guage Therapist; Educational Psychologist) approach to intervention. From this point, the

practitioner then needs to assess that risk, since research reviewed in this paper strongly

indicates that risk increases steadily with the number of language skills affected and with

the age to which impairment persists. A useful model for assessment of the risk associated

with early language delay is that proposed by Whitehurst and Fischel (1994). Whitehurst

and Fischel’s (1994) model demonstrates that long-term risk rises with age and degree of

impairment. Although the model does not assign precise values of risk to age impairment,

it does allow relative predictions. For example, a 2-year-old with expressive phonology

impairment is at low risk of severe and persistent language delay, and by implication at low

risk of poor outcomes in literacy; a 4-year-old with specific receptive-expressive language

delay is at moderately high risk of later literacy difficulties; and finally a 5-year-old with

secondary language delay (i.e., impaired nonverbal IQ) has the highest level of risk of

developing later literacy difficulties.

Whitehurst and Fischel (1994) recommend that practitioners make their treatment deci-

sions on the basis of such a model of predictive risk, and also within a cost-benefit matrix

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(i.e., is the cost of intervention justifiable, and will noticeable benefit accrue to the child?).

On the basis of this model, Whitehurst and Fischel (1994) argue for: (a) the restriction of

treatment of children under four years of age to those with secondary language delays; (b) the

restriction of treatment of children aged 4 or 5 to those with secondary language delays and

SRELD; and (c) the treatment of children with exclusively phonological problems only when

they have reached age 5 or 6. The authors justify their approach on the basis of their model of

risk outlined earlier, stating that resources need to be targeted towards those children with the

most severe and persistent language delays.

Whitehurst and Fischel’s (1994) model of risk allows practitioners and researchers to

make somewhat general predictions of risk for children with early language delay. How-

ever, Law et al. (2000) argue that models of predictive risk must be more rigorous than

this. They must allow the possibility of assessing risk in precise and quantifiable terms and

must be based on representative populations, rather than clinical samples. Such a model

would need to move beyond mere identification of factors which are associated with

language delay (e.g., gender), but rather move towards quantifying the level of risk at-

tached to each of these factors. Unfortunately there are only a few research studies which

have attempted to quantify risk in this way (e.g., Paul and Fountain, op cit.). With further

research taking this approach, Law et al. (2000) argue that the practitioner would then have

the tools to say that, given symptoms A, B and predisposing factors X,Y, outcome C, D

could be predicted given intervention Z.

IMPLICATIONS FOR FUTURE RESEARCH

In order to achieve a clearer understanding of the level of continuity between early language

delay and later literacy difficulties, future research must be rigorous and well-designed. First,

future research must take the form of longitudinal, prospective studies which follow children

from at least 2 years of age until the end of their school years (i.e., age 15/16 years). Second,

research must make distinctions between children with different types of language delay in

considering long-term outcomes. Third, greater research is required to investigate the long-

term sequelae of secondary language delay. Fourth, more stringent cut-off points are ne-

cessary in classifying children with language delay (Whitehurst and Fischel, 1994). Fifth,

each type of language delay should be clearly defined by researchers. Sixth, assessment

measures used in research should employ both standardised and functional techniques to

provide a more reliable indicator of language ability. Finally, future research should focus on

community samples as well as clinical samples.

CONCLUSION

The relationship between preschool language delay and later literacy development is com-

plex. To date, research attempting to unravel the nature of this relationship has provided

relatively clear conclusions. However, future research attempts need to take on board the

many limitations of earlier attempts, in order to provide practitioners with more sound evi-

dence on which to base their decisions regarding intervention. Unless such attempts are

made, practice will be reduced to an ‘imprecise science’ (Law et al., 2000, p. 180), leaving

practitioners to grapple with uncertainty regarding the best way to proceed in supporting

children with preschool language delay.

192 R. LARNEY

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