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COMMUNICATION DISABILITIESDevelopmental Language Impairment1

Session 1Course Tutor: James Law______________________________________________________________

Learning objectives of the session: To recognise the form/content and use framework and be able

to apply it to developmental language impairment (DLI) To be familiar with the terminology related to developmental

language impairment. To be aware of the range of different sub-classifications of DLI

– particularly the issue of specific language impairment (SLI). To be familiar with the main questions which have yet to be

answered in the field of DLI – most notably in the fields of early identification, prevalence and intervention.

IntroductionThe vast majority of children acquire language without any difficulty and this makes it possible to make generalisations about the course and nature of language development. However, for a sizeable number of children the process is not straightforward. It is this group which is the subject of these four lectures. There are a number of terms used for this group of children. On the one hand we find ostensibly medical terminology “congenital auditory aphasia” (Vaisse 1866), “congenital auditory imperception” (Worster Drought 1943) or “developmental aphasia” (Ingram and Reid 1956). On the other hand we find less value laden terminology such as “language delay” or “language difference” or even “language needs”. In the middle we have terms such as language disorder and language impairment. Developmental language impairment serves as an umbrella term for the other categories which may be differentiated both in terms of degree of difficulty and in terms of presenting symptoms.

What is developmental language impairment?A developmental language impairment represents a marked discrepancy between a child’s language skills and what would be expected for his or her age. In some cases the impairment is mirrored in that of other skills, such a motor skills, cognitive skills etc. Such cases are sometimes described as “general language impairments”. However it is also possible to identify children who have “specific language impairments”, that is they do not experience difficulties in areas other than language. The term “primary” language impairment is used for difficulties with no readily identifiable cause and the term “secondary” language 1 The emphasis in these sessions with be on “language” rather than “speech” , the latter being covered in greater detail elsewhere in the course.

Developmental Language Impairment – James Law – Course Notes 2001

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impairment is used for difficulties where the child experiences a condition which accounts for the associated language difficulty such as general learning difficulties, hearing impairment, cerebral palsy.

In defining the terminology it is important to recognise that we have to deal with two central issues.

The first is how delayed do you have to be to be considered language impaired – i.e. how do you identify cases in the first place? This is particularly important when you are trying to identify the right children in the population as a whole.

The second is that once you have identified a case how do you describe the child’s difficulties effectively such that it makes a difference as to what you do about it? This is particularly important because language impairments are “heterogeneous” in nature.

Note that this approach presupposes a highly functional approach. It does not follow that just because you can identify discrepancies between skills that children necessarily have problems. We are looking for the children who need support beyond that which is available under the status quo in existing provision. This can be a particularly problematic area especially for children who all receive educational services as a matter of course.

The ways that we can describe or assess these children in terms of their impairment and in terms of the context in which they develop are covered in more detail in the intervention course running parallel to this course. A most useful starting point is the Form/Content and Use Framework advocated by Bloom and Lahey and spelled out clearly by Lahey in Language Disorders and language Development (1988).

The SLI debateIt has long been recognised that a group of these children appear to have primary language impairment – ie impairment which occurs separate from any other difficulties. This is distinct from secondary language impairment which as the name suggests can be explained because of some other condition – eg cerebral palsy or general learning difficulty. A primary or “specific” language impairment is normally defined by exclusion. This means that:-

Hearing should be within normal limits (at least 25dB between 250 and 6,000hz)

Intelligence should be within normal limits There should be no obvious neurological symptoms (eg

cerebral palsy) No primary emotional problems No significant environmental component


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See Stark and Tallal (1981) for an application of these criteria which has remained in the literature.

In essence the term SLI is applied in three different ways.

1. Language is specifically delayed relative to non-verbal skills (so called cognitive referencing). This a child who is developmentally delayed but has verbal skills significantly below other aspects of his or her development could be said to have specific problems (eg Down Syndrome)

2. Language is specifically delayed relative to “normal” non verbal skills. The latter are measured on IQ measures. Normal is defined by convention to be at least one standard deviation below the population mean although some authors use two standard deviations. In essence it is this group that commonly is directly towards language units/resource bases.

3. One aspect of language is impaired relative to others. For example a child with phonological or syntactic impairment may be said to have a specific delay (relative to other language skills).

Be careful when you encounter the term SLI that you know how it is being used.

There has been considerable discussion in recent years about whether it is possible to identify impairment which are truly specific – Does specific language impairment (SLI) truly exist? See Conti-Ramsden, Donlan and Grove (1992) for an empirical report on the differing skills of children in a language unit. There are a great many issues well captured by Leonard (1987) and in his recent seminal work on SLI (Leonard 1998) and in a recent review by Plante (1998). See also the recent discussion of the relationship between SLI and motor impairments (Hill 2001).

What are the arguments for and against a specific deficit?..........

What are the common features of SLI?See Leonard 1997 for an over view and also Chiat 2000.

o Slow rate of lexical acquisitiono Poor verb processing (Conti-Ramsden and Jones 1997)


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o Poor grammatical development (especially in the use of inflectional morphology) (Marchman, Wulfeck and Ellis Weismer (1999),

o Poor performance on non-word repetition tasks (Bishop, North and Donlan 1996)

o Poor narrative skillso Poor verbal comprehension skillso Poor negotiation skills (Brinton, Fujiki and McKee 1998)

Classification SystemsEven if we are prepared to accept the concept of SLI clinical experience indicates that the children with SLI present in all sorts of different ways. This has led to attempts to “classify” SLI.

The most basic classification systems concern the distinction between expressive and receptive language skills. It is common to hear children described as having expressive language impairment or expressive/receptive language impairment (why no receptive language impairment?). It is also relatively common to hear a distinction being drawn between language delays and language disorders. The term “delay” suggests that the child is behind in their language development but the pattern is consistent with normal development and there is often an assumption that these children with “catch up” at a later date. The term delay tends to be used for preschool children.

By contrast the term “language disorder” or “language deviance “has suggested a more serious condition in which the sequence of language learning does not follow the normal pattern. The child’s language learning is effectively abnormal resulting in unusual linguistic forms and an increasingly distorted pattern of usage. Although this distinction is remains popular in some circles there is increasing evidence to suggest that they may not be discrete forms at all (Curtiss et al.1992).

Look at the literature to identify the key syntactic features of language delay and language disorder.

Once you have got beyond the identification process it is necessary to establish what type of language impairment the child is experiencing. A number of classification systems have been described. The most commonly recognised system is that described by Bishop and Rosenbloom (1987) and Rapin and Allen (1987) and shown in Bishop’s video film on the same subject.

What are the main characteristics of the following categories of language impairment?


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The classification system has found support in recent years (Conti-Ramsden et al 1997).

There are a number of issues around the adoption of classification systems which must not be ignored. It is likely that the classification systems overlap. Children probably don’t fit into one category or the other. More importantly we tend to see what we are most familiar with and many of these classification system have arisen from studies of quite a narrow range of children. It is clear that the nature of the impairment is likely to change across time, probably with the classification systems increasing in specificity as the child ages. For this reason some people are beginning to see developmental language impairment in terms of a model of risk and resilience. There are factors which predispose the child to difficulties such as a genetic predisposition and others which may optimise their chances of coping effectively with it. The way in which the impairment manifests itself is not constant over time. Different cognitive skills come into play at different times and these obviously affect the way


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RAPIN and ALLEN (1987) Classification system for SLI

Verbal auditory agnosia

Verbal dyspraxia

Phonological-processing deficit syndrome

Phonological-syntactic deficit syndrome

Lexical-syntactic deficit syndrome

Semantic-pragmatic deficit syndrome

the child copes with incoming information and the way in which they communicate with peers. At the end of this session are you:

o Clear how you can distinguish primary and secondary language disorder?

o Familiar with the concept of discrepancy criteria?o Familiar with arguments against discrepancy criteria?o Aware of the ways in which DLI has been subclassified?


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Reading for session 1:Bishop D, Rosenbloom L,(1987) Classification of childhood language disorders in Yule W, Rutter M, (eds) Language Development and Disorders Oxford; Mackeith Press

Conti-Ramsden G, Donlan C, (1992) Characteristics of children with specific language impairment attending language units European Journal of Disorders of Communication 27, 325-343

Conti-Ramsden G, Crutchley A, Botting N, (1997) The extent to which psychometric tests differentiate subgroups of children with SLI Journal of Speech Hearing and Language Research 40, 765-367

Curtiss S, Katz W, Tallal P, (1992) Delay versus deviance in the language acquisition of language impaired children Journal of Speech and Hearing Research 35, 373-383

Hill EJ, (2001) Non-specific nature of specific language impairment: a review of the literature with regard to concomitant motor impairments International Journal of Language and Communication Disorders 36,2,149-171

Leonard L, (1987) Is specific language impairment a useful construct? In Rosenberg S, Advances in Applied Psycholinguistics vol.1 Cambridge: Cambridge University Press

Mosciki, e. (1984) The prevalence of `incidence’ is too high. Journal of the American Speech and Hearing Association 26, 39-40

Plante E, (1998) Criteria for SLI: the Stark and Tallal legacy and beyond Journal of Speech Language and Hearing Research 41, 951-957

Rapin I, Allen D, (1987) Developmental dysphasia and autism in pre-school children: Characetristics and subtypes in Proceedings of the First International Symposium on Specific Speech and Language Disorders London: AFASIC

Stark R, Tallal P, (1981) Selection of children with specific language deficits Journal of Speech and Hearing Disorders 46, 114-122

Tomblin JB. Records, N. Buckwalter, P. Zhang, X. Smith, E. O’Brien, M. (1997) Prevalence of Specific Language Impairment in Kindergarten children Journal of Speech Language and Hearing Research 40, 6 1245


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COMMUNICATION DISABILITIES

Developmental Language Impairment

Session 2

Course Tutor: James Law______________________________________________________________

Learning objectives of the session: To be familiar with the issue of causation, what procedures we

use to establish causation and how much we know about the causes of developmental language impairment.

To be aware of the differences between causes of language impairment and associated phenomenon (correlations).

To be familiar with the idea of non linear multi-factorial causation.

IntroductionIn the previous session we saw how the population of children with developmental language impairment is described in terms of their language skills. It is now necessary to look at them more closely and try to tease out what is known about them from the point of view of aetiology and from the range of phenomenon which have found to be associated with language impairments.

AetiologyThere is now some considerable evidence about the inherently constitutional nature of language impairments. There are various ways of establishing this. The first is the physical examination of the brains of DLI children. In general this has relied on procedures for scanning the children’s brains such as Positron Emission Tomography (PET scans) or Magnetic Resonance Imaging (MRI) or more recently “functional MRI”. There is some evidence for symmetries in brain development where asymmetries would be anticipated (Locke 1994).

One area, which has attracted considerable interest in recent years, is that of specific molecular genetic markers for DLI or more specifically motor speech disorders. The most prominent evidence here comes from a single family – known as the KE family - in West London (Hurst et al. 1990, Tomblin and Buckwalter 1995, Vargha-Khadem et al. 1998). A particular site has been identified on the long arm of chromosome 7 (7q31). The search is now on to replicate this evidence. There are various levels of evidence. They usually start with co-occurrence within families, go on to twin studies and proceed to specific chromosome analysis. The co-occurrence evidence has now been accepted. In recent years there has come considerable supporting evidence from behaviour genetics, most


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notably the large scale TEDS study which has 3000 twin pairs (Plomin and Dale 2000). The evidence suggest that MZ (monozygote) twins have much migher level of “concordance” in term of their language abilities than DZ (dizygote) twins.

We also need to be aware of what might be called medical aetiology. A number of authors have picked out the adverse medical histories of these children both in terms of constitutional disorders such as epilepsy and what might be termed environmental factors such as otitis media with effusion. In the case of certain presentations of epileptic disorders specific speech and language disorders can follow (eg. Landau Kleffner Syndrome). We also know that low birth weight may be a contributory factor (Rocissano and Yatchmink 1983). Of particular interest here are “small for dates” babies (Largo and Howard 1986, Grunau 1990).

There is also evidence that these children have neuro-developmental lags – that is many aspects of their motor development and co-ordination are also moderately delayed and that language should be taken within this context (Bishop and Edmundson 1987 and the peg moving task).

An alternative explanation for language disorders relates to the work of Paula Tallal in the field of speech perception. In essence the argument runs that some children have a specific deficit (of constitutional origin) which prevents them from perceiving the speech input correctly. They process speech more slowly than other children and this has a dramatic effect on their processing of continuous speech. This, in turn, has a knock on effect on their ability to tune into the auditory signal, to pick up the meaning of new words, to extract saliency out of the speech signal and Developmental Language Impairment – James Law – Course Notes 2001

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What are the implications for clinical practice of the recent genetic findings?

The relative high heritability of language indicates that language is not just a matter of input.

It seems very unlikely that we are looking for a single gene.In most cases we are talking about “polygenetic inheritance”.

This may help parents concerned that they have caused the problems that their child is experiencing.

The environment is clearly important but only within certain parameters. Are their limits to the impact of intervention?

It looks as if there may be genetic support for early intervention.

There may be discussion of genetic screens for language impairment/autism etc. It is not clear at this stage how these could be implemented.

ultimately to a delayed use of language which has a cumulative effect on the child’s language development. Tallal and colleagues argue that this is true of all language impaired children and most importantly that it is effectively a learned strategy which is reversible.

Finally there is a distinct difference in the prevalence of speech and language difficulties in boys relative to girls. This is of the order of 3:1. A propensity for marked speech and language delays to be more common in males than females is generally confirmed by the studies reviewed in Law et al. 1998. Gender ratios derived are 1.25:1 (Randall et al. 1974), 2.26:1 (Stevenson and Richman 1976), 2.30:1 (Burden et al. 1996), 1.25:1 for both speech and language at four years (Stewart et al. 1986) and 2.3:1 (speech), with 1.2-1.6:1 (language) (Tuomi and Ivanoff 1977). There are two exceptions to this pattern. One of these is Beitchman et al. 1986 who found the reverse pattern for Speech only (0.98:1), Language only (0.98:1) and Speech or language (0.82:1) and a most unexpected 0.46:1 for the Speech and Language diagnosis. The other is Tomblin et al. (1997) who suggest that while boys are more likely to present with specific language impairment, the ratio is nearer equivalence. There are a number of possible explanations for these figures. The first is suggested by the design of the Beitchman study which sought to sample and then project the false negatives back into the original population sample. Of the false negatives, the majority were girls and in projecting back up to the main sample the authors projected the gender balance as well as the number of cases. A second explanation is that the relatively liberal cut-off effectively misses the commonly observed discrepancy between the genders because those cases found may be less likely to be true clinical cases and as such may tend to reflect the normal gender balance in the population. A third explanation and one favoured by Tomblin and colleagues is that existing data are the result of underreporting of difficulties in girls, a phenomenon which has also been reported in the literature related to reading disabilities (Shaywitz, Shaywitz, Fletcher, and Escobar 1990). The fact that the other major cohort study in this area did detect the predicted imbalance (2:1) adopting the fifth percentile as a cut off suggests that it may be the cut off which is the determining factor here rather than a high level of undetected difficulties in girls (Silva 1980). (For the full list of references consult Law et al. 1998)

What possible explanations might there be for the gender difference?

Factors associated with developmental language impairmentSocio-economic statusOver the class the role played by SES has been the source of considerable discussion much of it politically motivated. The most recent evidence (Hart and Risley 1995 Meaningful differences


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Baltmore: Paul Brookes) presents us with convincing evidence of the different role of verbal input in different social groups and the potential impact this may have on very young children’s language development. This evidence builds on a considerable amount of evidence derived from the Head Start Programmes in the US in the 1960s and 1970s suggesting that there are all sorts of aspects of the environment which need to be taken into consideration. Do these difficulties iron themselves out over the period that the children are in school or do differences in input translate into impairments? It is important that this issue takes us back to that of prevalence. Why?

Alongside the evidence concerning differences in parental input is that of environmental differences. Mayfield (1983) for example suggested that there are specific linguistic sequelae attributable to lead pollution. Diet has also be identified as a possible contributary factor. These factors are clearly SES related.

Currently in the UK no data is collected about the prevalence of language delay in different populations. It is not clear that more SLT services are available where greater disadvantage exists.

Parent/child interaction

Although this area is clearly related to SES (as far as Hart and Risley are concerned) it has tended to be treated discretely in the literature. Chomsky in his very early contributions to the debate about language acquisition has repeatedly argued that the role of input was essentially trivial. Children do not start speaking in the manner that their parents spoke to them but quickly generate their own syntactic forms because they were pre-programmed to do so. At one level they had to receive enough input but the threshold for this was probably very low. This position lead to decades of discussion about the precise role of parental (usually maternal) input. What are the characteristics of that input?

Child directed speech: Adult speaks to the here and now Limited vocabulary use Unnecessary words and unstressed words are omitted There are fewer word endings Utterances are grammatically simple Adult uses utterances which are slightly more grammatically

complex than those with the repertoire of the child Utterances are slowly and carefully enunciated Utterances are repetitive


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Given that language acquisition is universal how universal are these behaviours? And what does it mean if you do not exhibit them? Is it possible to inhibit a child’s develop by not using these features?

The linguistic evidence tended to suggest that while there was some evidence for very specific relationship between what the parent says and the child’s subsequent output (eg use of auxiliaries) there is little direct relationship between input and output. Rather child directed speech appears to help to focus the child on the verbal input in a general way.

What happens when children do not receive input at all or where is is actively negative? You need to be familiar with the cases of Genie and the Kulochova twins (see Skuse 1988 in Bishop and Mogford and for the story of Genie try Rymer 1993). For a review of the literature of the relationship between child abuse and neglect and language development see Law and Conway 1991.

Evidence from the population of language impaired children initially suggested that parental input for language impaired children was sparse and that the problem was therefore one of parental input. Wulbert et al. for example described parents and children “living together in parallel”. This is a powerful image but does it mean that the parent is ignoring the child or vice versa. Conti-Ramsden and colleagues have suggested that we should look at the issue from the other side. Parents follow the level of output of the child. They respond but they do not initiate if the child is not themselves responsive. This can lead to a downward spiral where the environment effectively is not supporting the limited output that the child brings to the interaction.

HearingAs we saw last session children with severe hearing losses do not tend to be classified as having developmental language impairment in the same sense as children with primary language impairments. However even if we exclude children with identified sensori-neural hearing losses it is still important to be aware that mild and intermittent conductive hearing losses are in the histories of many children with language delay. These are usually associated with coughs, colds and more specifically ear infections in the early years

Does this mean that all children with mild hearing losses are going to have language delay? Or are we more sensitised to this issue purely because children with identified hearing losses also have delayed language development?


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Cognitive skillsThere is a temptation to assume that if a child has a specific language impairment he or she will not have any associated non-linguistic cognitive difficulties. This is a complex issue which was touched on in the last session. There is a good review of the evidence here in Leonard 1997 (chapter 7).

An area which has attracted particular attention is the role of symbolic play. This can be seen as a non linguistic activity. Yet there is fairly convincing evidence that children with language impairments also exhibit immature symbolic play skills. If so what is the relationship between play and language? Some have argued that play like language is an essentially symbolic skill and that the language impairments and poor play skills are both attributable to a difficulty in symbolic processing.

Another interesting area is that of visual processing. Do children with language impairments also have difficulties with visual representations? The evidence seems rather more equivocal but there is some evidence that while language impaired children do not have difficulties with simple visual tasks they do have difficulties with what are known as complex hierarchical visual tasks. Are such tasks corollaries of the syntactic tasks that language impaired children find so difficult? It is also worth noting a line of argument deriving from the development of language skills in blind children. This evidence has been very recently reviewed in Perez-Pereira and Conti-Ramsden 1999.

BehaviourIt is commonly reported that children with language impairment also have behavioural problems. Why might this be?

Three mechanisms are suggested. Speech and language impairments lead to frustration on the part of the child in turn leading to behavioural difficulties. Alternatively the behaviour may lead to poor communication skills. Thirdly they may have a common neuro-developmental delay which affects both language and behaviour. In general the first and the third of these explanations are seen as the most likely. With the exception of selective mutism there is rarely a direct link from behaviour to language, but clearly this is likely to be a complex interactive process. For example poor interaction in the first months of life leads to poor attention skills in turn leading to poor early language skills, each effect having a knock on effect on the way that others communicate with the child.

ReadingOne of the most salient associations is between early language delay and literacy difficulties. In the most recent large scale study to address this issue Tomblin and colleagues found that reading and


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spokne language were strongly correlated (r=.68). 58% of a group of 164 DLI children were found to have such difficulties compared with 9% of 417 language normal controls. Clearly this sort of association has considerable ramifications for those working with children with reading difficulties in school.

English as an additional languageThis will be dealt with in greater detail later in the year. But given the proportion of people who have English as an additional language in the UK this is of considerable importance. There is no evidence which suggests that growing up in an environment with two or more languages commonly being used by those around you will lead to a clinical level of language difficulty. Indeed there has been some suggestion that it increases your awareness of language, your metalinguistic skills, and that this may have a positive knock on effect on language skills. However it is true that the learning of one language may affect the learning of another (eg. the cross over of vocabulary (see Genesee in Mogford and Bishop 1988) and there is often extensive discussion at a clinical level trying to unpick cause and effect when children when bilingual children are identified as language impaired.

Multidimensional modelsIn the majority of cases aetiology is not likely to be linear – ie. With a simple one to one correspondence between cause and effect. Instead it is more appropriate to see the model as multi-factorial with a basic propensity for language being increased or diminished according to factors in the individual’s environment. The critical issue here is to build a model of risk and protective factors. To do this it is essential that the widest range of domains of information is covered for each individual and that outcomes are tailored to the needs of the individual.

At the end of this session are you: Able to distinguish between causes and correlations? Familiar with the concept of aetiology and co-morbidity? Familiar with the most important factors common to children

with DLI?

Reading for session 2:

Hammer CS, Tomblin JB, Zhang X, Weiss AL, (2001) Relationship between parenting behaviours and specific language impairment in children International Journal of Language and Communication Disorders 36, 2, 185-207


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Hurst JA, Baraitser M, Auger E, Graham F, Norell S, (1990) An extended family with a dominantly inherited speech disorder Developmental Medicine and Child Neurology 32, 347-355

Law J, (ed) (1993) The early identification of language impairment London: Chapman and Hall

Leonard L, (1998) Children with specific language impairment Cambs, Mass: MIT Press

Locke J, (1994) The gradual emergence of language disorders Journal of Speech and hearing Research 37, 608-616

Nelson NW, (1993) Childhood language disorders in context: Infancy through adolescence London: Allyn and Bacon

Perez-Pereira M, Conti-Ramsden G, (1999) Language development and social interaction in blind children Hove: Psychology Press

Plomin R, Dale P, (2000) Genetics and early language development: A UK twin study of twins DVM Bishop and L.Leonard (Eds) Speech and Language impairments in children: Causes, characteristics, Intervention and Outcome Chichester: Psychological Press

Rocissano L, and Yatchmink Y, (1983) Language skills and interactive patterns in prematurely born toddlers Child Development 54, 1229-1241

Rymer R, (1993) Genie: Escape from a silent childhood London: Michael Joseph

Tomblin JB, Buckwalter PR, (1994) Studies of genetics of specific language impairment in Watkins RV Rice ML, Specific Language Impairments in Children Baltimore: Paul Brookes

Tomblin JB, Zhang X, Buckwalter P, Catts H, (2000) The association of reading disability, behavioral disorders, and language impairment among second grade children Journal of Child Psychology and Psychiatry 41, 4 473-482

Vargha-Khadem F, Watkins KE, Price CJ, Ashburner J, Alcock K, Connelly A, Francowiack RSJ, Friston KJ, Pembrey ME, Mishkin M, Gadian DG, Passingham RE, (1998) Neural basis of an inherited speech and language disorder Proceedings of the National Academy of Science 95, 12695-12700


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Session 3

Course Tutor: James Law

______________________________________________________________

Learning objectives of the session: To understand about the concept of prevalence To understand about the concept of natural history and why it

is important. To understand about the known sequence of language

impairment To understand about the range of interventions used in

treating language impairment. To understand about the known impact of language

impairment. To understand the relationship between the intervention and

the identification process.

PrevalenceHow many children have development language impairments? While this may not seem a very interesting question from the point of view of the individual speech and language therapist it is a central issue when it comes to determining who needs intervention. Prevalence refers to the number of cases in a given population at a given time. It is contrasted with incidence which corresponds to the number of new cases in a given population. It is very difficult to establish the incidence of developmental conditions without a universal method of establishing onset and a criterion for what is considered a case. Prevalence is conventionally expressed as the proportion or percentage of cases in a given population at a specified time. Normal rather than clinical populations are the focus in the present review. Prevalence differs from, but is often confused with, incidence which refers to the number of new cases (Moscicki 1984). Cases may move out of the pool from which prevalence is taken because of a number of mediating factors (such as spontaneous recovery, intervention or death) but prevalence also depends upon incidence. Prevalence will rise if incidence exceeds the decrease brought about by these mediating factors. Prevalence is an important concept for three reasons. It allows planning of service delivery. It should also allow calculation at an epidemiological level of the impact of intervention, with a successful intervention being one that results in a decline in prevalence. It should reflect current knowledge about a disorder, the parameters


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being determined but where the boundaries lies between normality and abnormality and which cases respond to intervention.

It is possible to establish prevalence in a number of ways – by asking clinicians, by asking parents, by assessing a whole population. To date this has proved problematic because we do not have a clear idea of which children will not improve if they are not identified as cases. We still tend to operate with rules of thumb which are recognised to have clinical validity. The most comprehensive summary of this literature comes in Law et al. 1998 and Law et al.2000). In this case the median figure reported was 5.95%. This is in line with most authorities which tend to agree that somewhere between 5 and 10% of children have low language scores which make them vulnerable to persistent speech/language and other difficulties. But note that some authors refer to much higher figures and some much lower figures. The figure currently most commonly reported in the US comes from Tomblin, Records, Buckwalter, Zhang, Smith and O’Brien (1997).

What is the impact of developmental language impairment?For a long time it was assumed that DLI was essentially a transitory phenomenon. Parents were told that children would simply “grow out of it”. In the last few years it has become apparent that this is not the case.

What sort of evidence would you need to address this issue?

Look at the following list and indicate where the bias might lie in interpreting this evidence.

The reports of parents. The reports of children (provided retrospectively). The reports of speech and language therapists The reports of classroom teachers Studies following children who have attended specialist

language provision. Studies following complete clinic caseloads Studies of whole populations.

At one level it is useful to ask parents. They might be said to provide the most valid judgement of their child’s abilities. The AFASIC Parent’s survey entitled Alone and Anxious (1993) gives you a clear idea of how frustrated parents feel both in communicating with the child and in fighting for services. They are clearly very acutely aware of the identification and labelling process. But does this tell us more about the parents than it does the children?

What we need is a clear indication of what happens to a group of children who are identified as being language impaired at say 2 or 3


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years when they are followed up into adulthood. These studies are now beginning to fill the gaps in our knowledge.


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Following up children in specialist language provision and other clinical provision.

There are many examples of this. The difficulties which they experience are associated with a number of antecedents in the health sphere and are linked to a range of educational outcomes most notably in socialisation and in the development of literacy (Beitchman et al. 1996, Bishop and Adams 1989, Fundudis, Kolvin and Garside 1979). For many the prognosis appears to be relatively good (King et al. 1982) especially for those with expressive language delays (McRae and Vickar 1991, Whitehurst et al. 1991). But outcomes appear to be more problematic for the group with more severe specific language delays. Stothard, Snowling, Bishop, Chipchase and Kaplan (1998) have suggested that a substantial proportion of children (80%) originally identified as having specific language impairment which persisted until 5;6 years were likely to go on to have persistent difficulties to 15 years and remained at risk of having more general learning difficulties at follow-up.

The focus for a number of the follow-up studies has been children identified as being in need of intensive intervention in the pre-school period in what are known in the UK as “language units”. In measuring outcomes two techniques are commonly used, standardised speech and language tests and educational placement. Evidence from children identified at primary school age suggests that the figure for those that are reintegrated into mainstream provision may be high - of the order of 80% (Bruges 1988, Stone 1992) and this is likely to reflect the severity of the initial difficulties and the age of the children. For example only 52% of children from a residential provision for children with severe specific language impairment returned to mainstream once they left junior school (Haynes and Naidoo 1991). The increased emphasis on integration has meant that there is a need to investigate this issue further, to move towards identifying what are the real strengths of the specialised language unit environment for these children and what the differences may be between those children who cope well in one environment relative to another. For example there is some evidence that those who stay in language units differ from those that moved to mainstream school in achieving significantly lower intelligence and literacy scores (Davison and Howlin 1997). Davison and Howlin (1997) raise the interesting question of the extent to which associated difficulties, most notably behaviour problems, also discriminate in terms of educational placement, the suggestion being that the lack of support in mainstream is likely to lead to behaviour problems. The suggestion is, therefore, that placement in mainstream may represent improvement but does not necessarily reflect normalisation or even an ability to cope with the educational, social and emotional demands of mainstream class


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Law et al. 1999 followed up a group of language impaired children and found a proportion to have resolved by the time they were going into secondary school.

But what does it mean to have a developmental language impairment that has resolved? There is some suggestion that even children who have apparently improved have not truly resolved (Joffe, Doyle, and Penn 1996). In particular there is evidence that children whose difficulties have apparently resolved continue to have poor phonological processing skills (Stothard et al. 1998).

Natural History“Natural history” is a specific term used to describe the prognosis of a condition in the absence of intervention (Gordis 1996). It can be a difficult concept when it comes to children’s development because, in most cases, children receive some form of intervention by virtue of entering the education system. Nonetheless there probably is a distinction to be drawn between intervention of a generic nature and intervention which is targeted at the child’s specific difficulties. Natural history is important because the anticipated status of a putative case allows determination of current status. Thus if two cases are identified as having comparable levels of skill at time one but it is known that there is a much greater risk of persistent problems for case one than for case two, then the relative weighting attributed to case one will be higher. Again the issue of natural history is dealt with in detail in Law et al. 1998.

At the end of this sessions are you:o Familiar with the difference between prospective and natural

history studies?o Aware of the difference between studies looking at population

cohorts and those following up confirmed “cases”?o Aware of the potential long term impact of DLI?


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Reading for Session 3:

Aram DH, Nation JE, (1980) Pre-school language disorders and subsequent language and academic difficulties Journal of Communication Disorders 13, 159-170

Beitchman JH. Wilson B. Brownlie EB, Walters H, Lancee W, (1996) Long term consistency in speech/language profiles 1: Developmental and Academic outcomes Journal of American Academy of Child Psychiatry 35:6 804-825.

Bishop DVM, Adams C, (1990) A prospective study of the relationship between specific language impairment, phonological disorders and reading retardation Journal of Child Psychology and Psychiatry 31 1027-1050

Bralley R, Stoudt R. (1977) A Five Year Longitudinal Study Of Development Of Articulation. Language, Speech And Hearing Services In Schools 8(3): 176-180.

Bruges A, The outcome of language unit placement: A survey in Avon 1987 Educational Psychology in Practice 4 85-90

Catts H, Kamhi AG, (1999) Language and reading disabilities London: Allyn and Bacon

Conti-Ramsden G, Botting N, Simkin Z, Knox E, (2001) Follow-up of children attending infant language units: outcomes at 11 years of age International Journal of Language and Communication Disorders 36,2,207-211

Davison FM, Howlin P, (1997) A follow-up study of children attending a primary-age language unit European Journal of Disorders of Communication 32, 19-36

Felsenfeld S, Broen P, McGue M. (1992) A 28-Year Follow-Up Of Adults With A History Of Moderate Phonological Disorder: Linguistic And Personality Results. Journal Of Speech And Hearing Research 35: 1114-1125.

Fey M, (1986) Language intervention with young children London: Taylor and Francis Nye et al. 1987, McClean and Woods Cripe 1997), Law 1997.

Fiedler M, Lenneberg E, Rolfe U, Drorbaugh J. (1971)A Speech Screening Procedure With Three-Year-Old Children. Pediatrics 48(2):268-276.

Gordis L, (1996) Epidemiology London: WB Saunders


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Hall N. (1996) Language And Fluency In Child Language Disorders: Changes Over Time. Journal Of Fluency Disorders 21:1-32.

Haynes C, Naidoo S, (1991) Children with Specific Speech and Language Impairment. Clinics in Developmental Medicine 119 Oxford: Blackwell Scientific

Huntley RMC, Holt K, Butterfill A, Latham C, (1988) A follow-up study of a language intervention programme British Journal of Disorders of Communication 23 127-140

Hall N, Yamashita T, Aram D. (1993) Relationship Between Language And Fluency In Children With Developmental Language Disorders. Journal Of Speech And Hearing Research; 36: 568-579.

Joffe BS, Doyle J, Penn C, (1996) The persisting communication difficulties of `remediated’ language-impaired children European Journal of Disorders of Communication 31, 369-386

King RR, Jones C, Lasky E, (1982) In retrospect: A fifteen year follow-up report of speech-language-disordered children Language, Speech and Hearing Services in Schools 13, 24-32

Law J, Boyle J, Harris F, Harkness A, Nye C, (1998) Screening for speech and language delay: a systematic review of the literature Health Technology Assessment 2, (9)

Law J, Boyle J, Harris F, Harkness A, Nye C, (2000) Prevalence and natural history of primary speech and language delay: fidnings from a systematic review of the literature International Journal of Language and Communication Disorders 35, 2 165-189

Law J, Durkin C, Sargent J, Hanrahan D, (1999) Beyond Early Language Unit Provision:Linguistic, Developmental And Behavioural Outcomes Child Language Teaching and Therapy 15, 2 93-111

McRae KM, Vickar E, (1991) Simple developmental speech delay: a follow-up study Developmental Medicine and Child Neurology 33, 868-874

Paul R, Cohen D, Caparulo BK, (1983) A longitudinal study of patients with severe developmental disorders of language learning Journal of American Academy of Child Psychiatry 22 525-534

Renfrew C, Geary L. (1973) Prediction Of Persisting Speech Deficit. British Journal Of Disorders Of Communication 8(1): 37-41.


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Rescorla L, Schwartz E. (1990) Outcome Of Toddlers With Specific Expressive Language Delay. Applied Psycholinguistics 11(4):393-407.

Richman N, Stevenson J, Graham P. (1982) Preschool To School: A Behavioural Study: London: Academic Press,

Scarborough H, Dobrich W. (1990) Development Of Children With Early Language Delay. Journal Of Speech And Hearing Research 33(1):70-83.

Silva P. (1980)The Prevalence, Stability And Significance Of Developmental Language Delay In Preschool Children. Developmental Medicine And Child Neurology 22:768-777.

Silva P, Mcgee R, Williams S. (1983) Developmental Language Delay From Three To Seven Years And Its Significance For Low Intelligence And Reading Difficulties At Age Seven. Developmental Medicine And Child Neurology 25:783-793.

Silva P, Williams S, Mcgee R. (1987) A Longitudinal Study Of Children With Developmental Language Delay At Age Three: Later Intelligence, Reading And Behaviour Problems. Developmental Medicine And Child Neurology 29: 630-640.

Stern LM, Connell TM, Lee M, Greenwood G, (1995) The Adelaide pre-school language unit: results of follow-up Journal of Paediatric Child Health 31 207-212

Stevenson J, Richman N. (1976) The Prevalence Of Language Delay In A Population Of Three-Year-Old Children And Its Association With General Retardation. Developmental Medicine And Child Neurology 18(4):431-441.

Snowling MJ, Adams JW, Bishop DVM, Stothard SE, (2001) Educational attainments of school leavers with a preschool history of speech-language impairment International Journal of Language and Communication Disorders 36 2, 173-185

Stothard SE, Snowling MJ, Bishop DVM, Chipchase BB, Kaplan CA, (1998) Language impaired pre-schoolers: A follow-up into adolescence Journal of Speech, Language and Hearing Disorders 41, 407-418

Stone E, (1992) A follow-up study of ex-pupils from a speech and language unit Child, Language Teaching and Therapy 8, 3, 285-313

Thal D, Bates E. (1988) Language And Gesture In Late Talkers. Journal Of Speech And Hearing Research 31:115-123.


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Thal D, Tobias S. (1992) Communicative Gestures In Children With Delayed Onset Of Oral Expressive Vocabulary. Journal Of Speech And Hearing Research 35: 1281-1289.

Thal D, Tobias S, Morrison D. (1991) Language And Gesture In Late Talkers: A One Year Follow-Up. Journal Of Speech And Hearing Research 34: 604-612.

Ward S. (1992) The Predictive Validity And Accuracy Of A Screening Test For Language Delay And Auditory Perceptual Disorder. British Journal Of Disorders Of Communication 27: 55-72.

Whitehurst GJ, Fischel JE, Lonigan CJ, Valdez-Menchuria MC, Arnold DS, Smith M, Treatment of early expressive language delay: If, when and how Topics in Language Disorders 11, 55-68


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Session 4

Course Tutor: James Law

______________________________________________________________

InterventionThe details of how intervention is provided in your intervention course. However an important component of our understanding of communication disabilities is what is known about effective intervention.

There are a number of questions which we need to address about intervention:-

Does it work and if so how ?

Which children will be affected by it and in what way?.

What is the impact of the individual therapist contributions to the process?

Some therapists maintain it is something of an unknowable art and that scientific enquiry has nothing to contribute to the discussion. This is almost certainly wrong. As the number of good quality studies in the field increases so does our knowledge of what does or does not work. At the level of the individual the purpose of intervention is to eliminate the condition or to reduce its impact. At the level of the population the purpose of intervention is to reduce the prevalence of developmental language impairment (or whatever the condition).

What sort of interventions are available? There are a number of different ways of dividing them up. For example, it is possible to look at those aimed at younger or older children, those which do or do not involve the parents, those which are direct (in the sense that they work through the speech and language therapist) and those which might be termed indirect (in that they work through a third party – teacher or parent). The different interventions will be described in further detail in your clinical tutorials and you will develop a clear understanding once you have honed your clinical experience. The interesting issue from the point of view of the argument here is “do we know that intervention can be shown to


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make a difference”? Effectively can it alter the course of the natural history?

What evidence would we need to address this issue? What would we accept? In many ways this then becomes an issue of research design. Law et al. 1998 cover it in detail in the most recent summary of the complete world literature in this field but see also Fey (1986) Nye et al. 1987, McClean and Woods Cripe 1997), Law 1997.

In summary there is some pretty good evidence that intervention works better than nothing for some children – most notably children with expressive language delays. It is clear that intervention needs to be administered by an SLT when a child has a speech difficulty. When it comes to language difficulty working with parents appears to be just as useful. We do not yet have enough evidence to say whether early intervention is better that later intervention. Of particular interest here is work on a programme called the WILSTAAR (Ward 1999 International Journal of Language and Communication Disorders 34, 243-264 and correspondence in the same journal pp 441-447). Likewise we could not be sure whether there are some groups that we know SLTs are better at working with that others. We do not know enough about the role of SLT in groups that are known to be more persistent (i.e. children with expressive/receptive difficulties, children with autism or children from low SES backgrounds. Particular important we do not know whether it is more effective to have SLT providing intervention to school children or whether it really is more effective to have them integrated in mainstream schools.

In other words there are more unanswered than answered questions but a start has been made. You will be hearing much more detail about the procedures used in the Intervention course.

Remember lack of evidence is not the same as negative evidence!Intervention in educationThe interventions referred to above tend to be “clinically” focussed – that is they tend to be carried out by a specialist speech and language therapist with individuals or groups of children. The target of the intervention is customarily the removal of the problem. However once children go into the educational system this type of intervention may not be recommended because there is insufficient time or because such interventions do not match up to the aims of the National Curriculum. Accordingly it is critically important to consider the role of what might be termed “ecological” interventions set within larger systems – ie. the classroom. These will be covered in more detail elsewhere but just as it is important to think of assessment relating to a number of different levels in the child’s


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experience so too we must consider more broad based interventions.

This a major issue for teachers and therapists working together today and it has thrown up a number of issues which have recently been addressed by the Speech and Language Therapy Working group set up by the DfEE and the DH and which will be publishing its report during the current term. This group also commissioned a research study on the way in which health and education services relate to one another in the provision of services to children with speech and language needs.

Summary Evidence to date suggests that there is a lot of developmental

noise in early language development. In part the intervention may serve primarily to reduce that

noise. Intervention probably results in measurable effects when it is

possible to isolate FORM, CONTENT or USE. The more enmeshed the difficulties in the three areas are the less likely it will be that focused intervention will remove a child’s difficulties. In such cases a more systemic model may be more appropriate but the effects of such models are by definition more difficult to capture.

We know least about how to affect the development the most persistent cases.

Although we can be sure that intervention can impact on the individual, it is not clear the extent to which intervention can alter the course of natural history or effective result in a decline in prevalence. For many the real benefits are likely to be in the field of tertiary prevention – preventing the impact of the impairment rather than removing the impairment altogether.

At the end of this session are you:o Familiar with the concept of intervention and its objectives?o Broadly aware of the potential effects of intervention?o Aware of the problems associated with the design of some

studies?o Aware of the apparent contradiction between good

intervention results and poor prognosis?o Familiar with some of the differences between clinical and

educational interventions for children with DLI?


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Reading for Session 4:-

There are a great many papers around the issue of intervention. Many are descriptive and while interesting do not give compelling proof of the value of intervention. The following are chapters/papers that have attempted to summarise the current position.

Enderby P Emerson J (eds) (1995) Does speech and language therapy work? Whurr Publishers: London

Glogowska M, Roulstone S, Enderby P, Peters TJ, (2000) Randomised controlled trial of community based speech and language therapy in preschool children British Medical Journal 321 923-926 together with Law J, Conti-Ramsden G, (2000) treating children with speech and impairments: six hours hours of therapy is not enough British Medical Journal 321 908-909

Law J, (1997) Evaluating intervention for language impaired children: a review of the literature European Journal of Disorders of Communication 32: 404-412

Law J, Intervention for children with communication difficulties in Law, J, Parkinson A, Tamnhe R, Communication Difficulties in Childhood Oxford: Radcliffe Press

Law J, Boyle J, Harris F, Harkness A, Nye C, (1998) Screening for speech and language delay: a systematic review of the literature Health Technology Assessment 2, (9)

McLean LK, Woods Cripe JW, (1997) The effectiveness of early intervention for children with communication disorders. In: Guralnick MJ (ed) The effectiveness of early intervention Baltmore, Maryland: Paul Brookes

Nye C, Foster SH, Seaman D, (1987) Effectiveness of language intervention with language/learning disabled children Journal of Speech and Hearing Research 52, 348-357

Ward S, (1999) An investigation into the effectiveness of an early intervention method for delayed language development in young children International Journal of Language and Communication Disorders 34 3 243-265


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