Language in adults with Down syndrome
Jean Rondal and Annick Comblain
In this paper, we will try to supply at least a partial answer to the three following questions. First, what language levels are reached by adults with Down syndrome? Second, is there progress in language or some aspects of it beyond adolescence and during the adult years? This question is related to the issue of a critical period for language development raised by Eric Lenneberg (1967). Third, what is the effect of ageing on the language of persons with Down syndrome, including those who develop Alzheimer disease in old age?
Rondal JA, Comblain A. Language in adults with Down syndrome. Down Syndrome Research and Practice. 1996;4(1);3-14.
The population incidence of Down syndrome has not changed substantially over the
last decades. It is approximately 1/750 live births in both sexes (Dolk et al., 1990). Down syndrome
is still estimated to be the aetiology of up to 30% of moderately and severely intellectually
impaired individuals. However, life expectancy in Down syndrome has increased dramatically.
According to Oliver and Holland
(1986), it was 9 years in 1929, 12 to 15 years in 1947, and 18 years in 1961 (with
two thirds of the children dead by the age of twelve,
Carter, 1958). At present, as many as 70% of individuals with Down syndrome
may expect to live beyond 50 years (Mann
and Esiri, 1988), 44% will survive to the age of 60 years, and 13.1% to
68 years, compared with 86.4% and 78.4%, respectively, for the general population,
irrespective of sex (Baird
and Sadovnick, 1988). As a consequence of this evolution (determined largely
by medical progress, enhanced social awareness, within-family rearing, and early
and continued quality stimulation and education), it is expected that between the
years 1990 and 2010, the number of persons with Down syndrome over the age of 40
years will increase by 75%, and over 50 years by 200% (Steffelaar and Evenhuis, 1989).
These are encouraging indications for those who believe in the absolute right of
all human beings to live and to develop to their best potentialities. They also
make it all the more necessary to gather comprehensive data (medical, psychological,
social, etc.) on adults with Down syndrome in order to evaluate more precisely their
functioning capacities, the possible evolution of these capacities in time, and
to ensure the best possible social, emotional, and vocational adjustment of these
individuals. Language may have a particularly important role in these adjustments.
Some people (e.g.,
Swetlik and Brown, 1977) claim that impaired language and communication
skills constitute the major impediments to the integration of intellectually impaired
citizens in society. More studies of adults with Down syndrome are urgently needed
in order to meet the above challenge.
Before reviewing the available data, a word of caution is necessary. First, the
data on the language abilities of adults with Down syndrome are still limited and
one should be cautious in generalizing any conclusion from these data. Second, a
kind of "cohort caveat" is possibly involved in the question at stake.
Most adults with Down syndrome as of today, have not benefited from early educative
intervention, simply because such programs were not in existence 25 or 30 years
ago. Assuming at least minimal long range positive effects from such intervention,
it is likely that future adults with Down syndrome will demonstrate higher performance
levels (language and otherwise) than present-day adults. It would be a mistake to
use the empirical indications available today on the capabilities of adults with
Down syndrome as if they were genuine norms of ultimate achievement.
Language levels in adults with Down syndrome
Comblain (1994) gathered systematic language data in a sample of French-speaking
subjects (females and males) from the Liege area, in Belgium. There were 11 children
(8 girls, 3 boys) aged 6 years 10 months to 12 years 10 months, 16 adolescents (9
girls, 7 boys) aged 14 years 5 months to 21 years 6 months, and 15 adults (9 females,
6 males) aged 23 years 9 months to 42 years 10 months. Twelve intellectually impaired
children (7 girls, 5 boys), with chronological ages (CAs) between 3 years 7 months
and 7 years 4 months, matched with the children with Down syndrome on social class
and mental age( MA) [at the EDEI - Echelles Differentielles d'Efficience Intellectuelle
and Mises, 1974], served as controls on some of the tests. All the subjects
with Down syndrome had standard trisomy 21. The non-adults were attending primary
or secondary special schools for the intellectually impaired. The adults were attending
"La Fermette", an occupational day centre for adults with Down syndrome
located in the vicinity of Verviers, in the Eastern part of Belgium. They all appeared
to have normal or close to normal hearing and visual abilities (no specific examination
was undertaken) and came mainly from middle-class families.
The language measures (administered in a randomized way) included: mean length of
utterance (MLU) obtained from free-play or conversational speech, TVAP (Test de
Vocabulaire Actif et Passif,
Deltour and Hupkens, 1980; a receptive test of referential lexical knowledge),
TVP (Test de Vocabulaire Productif,
Comblain, 1993; an expressive test of referential vocabulary in which subjects
are requested to label as many as 817 pictures representing common objects or actions,
and corresponding to 20 basic semantic categories), as well as 8 receptive subtests
from the difficulty level 1 of the BEMS (Batterie d'Evaluation Morpho-Syntaxique,
Comblain, Fayasse, and Rondal, 1993). These subtests concern: the comprehension
of personal pronouns, definite and indefinite articles, verbal inflexions, coordinate
clauses, temporal locative, causal, and conditional subordinate clauses, relative
clauses, negative and passive sentences. The subjects are requested either to select
the picture most appropriately corresponding to the meaning of the proposed sentence
in some subtests, or to act out the sentence with play material in some other subtests.
The resulting data are summarized in Table 1. Only the data on adults with Down
syndrome are of immediate interest.
Table 1. Group means and standard deviations (between parentheses)
for the measures computed by Comblain (1994) on the language of Down syndrome (DS)
children, adolescents, and adults, and non-intellectually impaired children matched
with the children with Down syndrome on mental age and social class.
impaired children (11)
with DS (11)
with DS (16)
Chronological age (CA)
Mental age (MA)
Mean length of utterance (MLU) -
4.73 (2. 98)
45.83 (17. 94)
CA, MA, and TVAP ages are expressed in years and months;
MAs are global scores obtained at the EDEI; categories 5 to 13 are expressed in
percent of correct answers;
MLU is computed in number of words plus grammatical morphemes (according to Rondal,
Bachelet & Peree's procedure, 1986);
TVAP: Test de Vocabulaire Actif et Passif;
TVP: Test de Vocabulaire Productif;
Categories 6 to 13 are from the BEMS (Batterie d'Evaluation Morpho-Syntaxique);
Dots indicate categorical data that were not collected.
ANOVAs and follow-up analyses (Fisher LSDP) indicate that the following contrasts
are significant at the p< or =.05 level: non-intellectually impaired and children
with DS on indices 7, 9, 10, 11; non-intellectually impaired children and adolescents
with DS on indices 6, 7, 10, 11, 12, 13; non-intellectually impaired children and
adults with DS on indices 6, 7, 10, 11, 12, 13; children with DS and adolescents
on indices 3, 4, 9, 11, 12; children with DS and adults on indices 3, 4, 5, 9; adolescents
with DS and adults on indices 10, 13.
Receptive lexical development in intellectually impaired persons is often reported
to be consistent with mental age (MA). Comblain's data (items 3 and 4 on Table 1)
reveal a mean receptive lexical age of about 5 years on the TVAP, which is about
the MA level assumed to be reached by most adults with Down syndrome (cf. Gibson, 1978). On the expressive side, the adults
with Down syndrome studied by Comblain could label correctly approximately 50% of
the common objects and actions proposed. When it comes to lexical representation
and organisation, however, the picture may be even less favourable. Indeed, there
is no clear indication at this time that the mental lexicon of intellectually impaired
(including Down syndrome) individuals is structured in functionally appropriate
ways (see Barrett
and Diniz, 1989, and Rondal,
l994b, for relevant data and theoretical suggestions concerning the
hierarchical organisation, prototypicality, and the syntagmatic-paradigmatic dimension
of the lexicon of intellectually impaired subjects).
Table 2. Group means and standard deviations (between parentheses)
for the measures computed by Rondal
and Lambert (1983) on the language of Down syndrome (DS) and intellectually
impaired non-Down syndrome adults in free conversation with a non-intellectually
impaired adult interlocutor.
Adults with DS
Proportion of sentences
Correct marking of number and gender
Proportion of correct articles
Proportion of correct pronouns
Proportion of correct verbal inflexions
Proportion of information
Proportion of new information
Conversational topic continuity
1: TTR (type-token ratio): ratio of the number of different words (types) to the
number of words in a speech sample (tokens);
2: MLU: mean length of utterance, computed in number of words plus grammatical morphemes
according to Brown's rules (1973);
3: ratio of the number of sentences to the total number of utterances;
4: ratio of the number of compound verbs plus subordinate clauses to the total number
of utterances; indices
5 to 8 are proportions computed on the total number of utterances;
9: ratio of the number of items of information supplied verbally to the total
number of utterances [by information, it was meant a relational meaning in the sense
of Chafe's (1970) meaning analysis];
10: ratio of the number of items of information not previously stated in the verbal
exchange between interlocutors to the
total numbers of items of information given in the speech sample;
11: proportion of times the intellectually impaired individual correctly followed
in the exchange on the topic introduced by the interlocutor.
Another lexical measure, type-token ratio (TTR), assessing lexical diversity of
use, was computed by Rondal and
Lambert (1983) on corpora of spontaneous (conversational) language from
22 French-speaking adults with Down syndrome. Table 2 supplies a summary of the
quantitative observations in this study. Only Down syndrome TTR data are of immediate
As indicated in Table 2, observed TTRs are close to .58. This
figure is difficult to interpret for lack of normative data in (adult) French-speaking
or even English-speaking subjects. They can be compared to Rondal's TTR data obtained
from free speech in American- English speaking children with Down syndrome in free
play or conversation with their mothers (i.e. .44 for children younger than CA 6
years and .49 between CAS 6 and 12 years.
As to thematic semantics, adults with Down syndrome (see Rondal, 1978;
Layton and Sharifi, 1979;
Duchan and Erickson, 1976) appear to structure their utterances
- no matter how formally limited they may be - according to the same basic semantic
relations as non-intellectually impaired people (i.e., agent, semantic object, instrumentation,
beneficiary, location, attribution, etc.). They also seem to understand correctly
the same set of basic structural meanings when these meanings are expressed in the
speech of other people. There is no indication that the elementary semantic-structural
basis of language is markedly different in non-intellectually impaired and Down
syndrome persons at corresponding levels of language development.
To return to Table 1, mean MLU for the group of adults with
Down syndrome studied by Comblain (1994) is 4.73
with a standard deviation of 2.98. This is compatible with the corresponding figures
reported by Fowler (1988) and
Fowler, Gelman, and Gleitman (1994) for their late adolescent English-speaking
Down syndrome subjects (MLU in the range of 3 to 3.50), but slightly lower than
the figure reported by Rondal and
Lambert (1983) with a group of young French-speaking adults with Down syndrome
(i.e. mean MLU 5.98, SD 2.62; cf. Table 2). MLU in intellectually
impaired adults, as observed in free conversation, is usually in the vicinity of
12 words plus bound grammatical morphemes (according to the counting procedures
proposed by Brown, 1973,
Rondal, Bachelet, and Peree, 1986). The important limitation in Down syndrome
adults' MLUs reflects the formal simplicity of their utterances. It corresponds
most characteristically to the limited use of clause co-ordination and subordination,
the frequent lack or instability of grammatical morphemes (within the noun as well
as the verb phrase), the frequent lack of phrase and clause connectors, and of course
the overall reduced productivity of the language system. This is confirmed in the
study by Rondal and Lambert
(1983) already mentioned.
In this study, it was observed (see Table 2) that only about
half of the utterances produced by adults with Down syndrome were grammatical clauses.
Sentence complexity remained low. Grammatical marks of number and gender were produced
on the average only once in two or two times in three utterances. Articles are used
infrequently and verbs were not regularly inflected. Incidentally, in
Rondal and Lambert's (1983) study (as illustrated also in Table
2), non-Down syndrome intellectually impaired (of mixed and/or unknown
aetiologies) obtained scores generally higher on average than those of CA-matched
Down syndrome adults. This is consistent with the suggestion sometimes made that
the Down syndrome condition is more detrimental to language development than other
pathological entities in moderate and severe intellectual impairment [see
Fowler, (1990), and Kernan, (1990), for
recent re-activations of this suggestion dating back at least to
Zisk and Bialer, (1967)].
An interesting question is why the formal instability, particularly at the morphosyntactic
level, in the expressive language of individuals with Down syndrome?
Rondal (1985) (also see
Rondal and Edwards, in preparation) suggested that at least a part of
the explanation may reside in a too narrow processing capacity constraint in Down
syndrome (and intellectually impaired) subjects limiting rather drastically the
speaker's ability to allocate proper attentional and cognitive resources to the
ongoing formal monitoring of language, hence the token-to-token inconsistency of
grammatical productions. The more demanding the extralinguistic context, the nature
of the speech act performed, and the content and formal aspects of the language
to be produced, the more likely some of the less solidly established morphosyntactic
features will tend to be eliminated from the productions or will cause errors.
At the textual (or discursive) level, little data are available. They suggest major
expressive difficulties with regard to the paragraphic and discursive organisation.
Text macrostructure is often poorly dealt with (for instance, in narrative activities,
the usual sequential narrative structure is not regularly used, at times rendering
comprehension problematic for the unfamiliar interlocutor). Text cohesion is often
wanting by default or inappropriate use of standard cohesive devices (i.e., coreference,
ellipsis - and presupposition -, conjunction, lexical cohesion; see Halliday, 1985).
Major problems exist also in sentence comprehension. As Table 1
indicates, on the BEMS, adults with Down syndrome give less than or equal to 50%
correct responses in average value (with relatively important standard deviations
for some linguistic categories, however) in the following categories: personal pronouns,
articles, verbal inflexions, subordinate clauses, negative and passive sentences.
Receptive performance is slightly better on relative clauses. These data confirm
that the formal limitations observed in the expressive language of adults with Down
syndrome also extend to the receptive side of the language.
Articulatory and phonological skills in adults with Down syndrome seem to correspond
closely to those of children and adolescents with Down syndrome. The same speech
characteristics, errors, problems, and reduced intelligibility are reported for
adults with Down syndrome as for younger persons with Down syndrome. For instance,
Shriberg and Widder (1990),
and Hamilton (1993), for American English and
English-speaking subjects with Down syndrome, respectively, and
Van Borsel (1993), for Dutch-speaking adults with Down syndrome, all signal
comparable consonant error rates and typical speech errors largely on the same types
of phonemes (i.e., syllable final phonemes, consonant clusters, substitutions, additions,
and omissions of particular phonemes). Hamilton's
(1993) detailed technical analysis suggests the existence of several abnormal articulatory
characteristics in adults with Down syndrome, such as more palatal zone contact
for alveolar sounds (/t, d, n, I/), longer closure duration for occlusive consonants,
larger consonant transition times within clusters, difficulty with rapid tongue
movements, etc. Hamilton (1993) confirms the
existence of symptoms of dysarthria (i.e., breakdown in the ability to move the
tongue and lips in order to articulate speech sounds accurately and rapidly), and
dyspraxia (i.e., the ability to select, plan, and sequence the sounds needed in
speech). In addition, Shriberg and Widder
(1990) report abnormal suprasegmental characteristics, regarding five prosodic domains
(i.e., rate of speech, stress, loudness, pitch, and quality of voice - relative
harshness, hoarseness, or nasality) in the speech of their intellectually impaired
and adult Down syndrome subjects.
Stuttering is also relatively frequent in adults with Down syndrome (perhaps even
more frequently in males with Down syndrome) (see
Preus, 1972). It may be that the incidence of stuttering increases slightly
in individuals with Down syndrome from childhood to adulthood for reasons that are
not known at the present time, but may have to do with increasing social and personal
pressures in non-institutionalized Down syndrome adolescents and adults bearing
on immature speech systems.
Lastly, regarding the pragmatic and linguistic communication levels of adults with
Down syndrome. Limited information is currently available at this time on this topic.
A good deal of the available information is summarized and discussed in Rosenberg
and Abbeduto (1993). Some information on conversational topic continuity and topic
contribution in Down syndrome adults' conversations were also gathered by Rondal
and Lambert (1983) - see Table 2 here, lower portion. It is
possible to summarize briefly this literature attesting to the nontrivial nature
of Down syndrome persons' abilities in the pragmatical aspects of language and ordinary
communication, as done in Table 3.
Table 3 - Levels of language pragmatic functioning in adults
with Down syndrome.
Level of functioning
1. Speech acts
A. Individuals with Down syndrome are able to question, request, answer, assert,
suggest, command, acknowledge, commit themselves, purpose, and express feelings
or opinions, like non-intellectually impaired people, but with primitive linguistic
means, and not always using the indirect, softened, polite, or inferred forms that
normal people find appropriate.
B. Receptively, individuals with Down syndrome eventually become able to understand
speech acts in familiar interactions and settings but only associated with simple
linguistic cognitive and social demands.
2. Repairing communication
Individuals with Down syndrome by adulthood seem to have the skills necessary for
responding to a variety of requests for repair and to request repair of conversational
3. Conversing and
Individuals with Down syndrome exhibit appropriate turn-taking behaviours in familiar
conversational situations. They evidence conversational topic continuity with peers
as well as non-intellectually impaired interlocutors, and they can meaningfully
contribute to the
conversational topic. Information supplied and organized discursively do not seem
to be more redundant than customary speech between familiar non-intellectually impaired
In summary, it seems possible to characterize the language of most adults with Down
syndrome as formally restricted (particularly morphosyntactically), often deficient
as to articulation and phonological processes, but semantically, pragmatically,
and communicatively appropriate to minimal cognitive and social demands. Utterances
are typically short (with MLUs around 5), monopropositional, with limited and inconsistent
use of grammatical morphology. Purely linguistic comprehension is drastically limited
rendering the reliance on lexical, informational, and situational cues all the more
important. Despite such drastic shortcomings, the semantic structures and the contents
of the utterances produced are correctly organized, the verbal production is informative,
relevant, and generally appropriate to the social context and the communicative
intents of the locutors. In particular, the major speech acts and conversational
functions are accessible to the adults with Down syndrome even with reduced lexical
and grammatical means.
No systematic comparison has been published to the best of our knowledge of the
language of male and female adults with Down syndrome. It is not possible therefore
to establish at the present time whether significant language differences exist
between men and women with Down syndrome. In my view, such differences are unlikely
except perhaps in the articulatory and intelligibility aspects of language (including
stuttering and dysfluencies), possibly more frequent in males with Down syndrome,
which may be the objective basis for the not uncommon opinion in educators and parents
(e.g., Buckley and
Sacks, 1987) that boys with Down syndrome are less well off with language
Actually, available studies involving systematic language comparisons of intellectually
impaired boys and girls (including those with Down syndrome) (see
Rondal and Edwards, in preparation, for a review and discussion) reveal
little sex variation in a long list of speech and language features, except precisely
on stuttering and dysfluencies often reported as being more frequent in intellectually
impaired and Down syndrome males (e.g.,
Stansfield, 1990), which is also the statistical situation in non-intellectually
impaired people (and may incriminate slightly greater fragility of some brain speech
structures in men).
Also, as is known, Down syndrome is not an homogeneous entity at the cytogenetic
and etiological level. Standard trisomy 21 (ST21) represents approximately 97% of
the cases. In 1 or 2% of the cases, depending on the epidemiological studies, the
genetic error takes place during the second or the third cell division (mosaicism).
In the remaining 1 or 2% of the cases, the additional chromosome material is not
a triplicate of chromosome 21 but a part or the totality of another chromosome (often
chromosome 14 or 22). These are cases of translocation. We know that ST21, mosaicism,
and translocation subtypes of Down syndrome display differences in dermatoglyphic,
physical, clinical, and mental status (see
Gibson and Pozsonyi, 1965;
Baumeister and Williams, 1967;
Fishler, 1975). Possible variation in language development and functioning
could be expected depending on the aetiological subtype. Few specific data exist
on this question unfortunately. They seem to suggest (e.g., Fishler and Koch, 1991) better
lexical and semantic abilities in children and adolescents with mosaic Down syndrome,
probably in proportion to their usually more advanced intellectual abilities (for
reason of a neurological heterogeneity genetically based and developmentally mediated
- with the other subtypes of Down syndrome). No follow-up data are available concerning
possible speech and language differences in adults with Down syndrome according
to subtype of Down syndrome.
Lastly, it is important not to minimize the extent and generality of the inter-individual
differences in the language functioning of persons with Down syndrome (exemplified
in the relatively large SDs reported in the empirical studies; see
Tables 1 and 2 above, for example). Such a variation
must be taken into account theoretically and also practically, for example when
planning social and work integration, leisure activities, and further education
for those persons. At rare times, such individual differences may culminate in exceptional
cases of language development and functioning in persons with Down syndrome (e.g.,
Seagoe, 1965, 1993; Rondal, 1994b) - there are corresponding exceptional
cases language-wise in non-Down syndrome intellectually impaired subjects (e.g.,
Bellugi, Marks, Bihrle, and Sabo, 1988;
Bellugi, Wang, and Jernigan, 1993;
Curtiss, 1988; Cromer, 1991;
Yamada, 1990). Most astonishingly,
for example, FranÃ§oise the adult woman with Down syndrome studied by us, presents
well-developed - to the point of being normal or normal like - computational language
components, to use Chomsky's formula (i.e., phonology and morpho-syntax), expressively
as well as receptively. Her language conceptual aspects (i.e., vocabulary and lexical
abilities) and discursive abilities are more in correspondence with the limited
Cases such as FranÃ§oise and a few others (and it would seem that there are others
"in store" awaited to be documented) constitute potent arguments in favour
of the modular conception of language and the relative developmental autonomy of
phonology and morpho-syntax, as suggested by authors such as
Liberman and Mattingly (1989), Chomsky (1981,
Moscovitch and Umilta (1990). In a more applied way, they strongly suggest
that the extent of neurological heterogeneity in Down syndrome may be quite large,
and even larger than expected. The specification of brain development in Down syndrome
in a functionally oriented way is becoming a priority for advancing our comprehension
of cognitive and language functioning (among other functions) in persons with Down
syndrome. Also, systematic cognitive and language neurobiological comparisons of
other intellectually impaired syndromes should be encouraged (such as the recently
published study of Down syndrome and Williams syndrome subjects from neuropsychological,
neurological, and neuroanatomical points of view by
Bellugi, Bihrle, Jernigan, Trauner, and Doherty, 1990).
Language progress in adults with Down syndrome
Is there spontaneous language progress in individuals with Down syndrome beyond
adolescence and in adulthood? The answer to this question conditions the way we
should plan further education for persons with Down syndrome beyond the early years.
It is also reminiscent of the question of a critical period for language development
as raised by Eric Lenneberg some years ago (1967),
a question that is still with us with great acuity.
In the absence of longitudinal observations running from childhood into adulthood,
the only way to answer (tentatively at the present time) the above question is to
compare the language of adults with Down syndrome, backwards so to speak, to the
language of adolescents and children with Down syndrome. In so doing, one is exposed
to the criticism of applying a cross-sectional method to a longitudinal problem,
and one is therefore liable to the usual reservations. But this is the only way
open to us at present. In what follows, we will report the indications on the language
of Down syndrome adults to that of Down syndrome adolescents and children in an
attempt to provide a first answer to the life-span "progress or evolution question"
as raised above (see also
Summarizing a number of comparative research data originating in the work of Van
Borsel (1988, 1991), Comblain
(1994), Rondal et al. (1981), Rondal
and Lambert (1983), in addition to the series of studies on pragmatical
and linguistic communication in intellectually impaired (including Down syndrome)
children, adolescents, and adults reviewed by
Rosenberg and Abbeduto (1993), it seems that no progress can be ascertained
in the receptive morphosyntactic aspects of the language of Down syndrome adults
when compared to Down syndrome adolescents.
On the expressive side of morpho-syntax, the data are also consistent with the null
hypothesis regarding developmental progress from adolescence to adulthood. No progress
is obvious either in the phonological aspects of language in the adult years. In
this respect, the empirical reports (e.g.,
Hamilton, 1993; Van Borsel,
1993) - in different languages - insist on the persistence of the same
speech problems across the years. The conceptual and pragmatical aspects of language
may offer a different developmental picture, however. No progress in receptive and
expressive referential lexicon is attested in Comblain's (1994) data with adolescents
and adults with Down syndrome (see Table 1 above), nor in
diversity of lexical use [if one compares the spontaneous speech of intellectually
impaired (including Down syndrome) adults and adolescents in the data of
Rondal and Lambert, 1983, and Rondal et al., 1981].
However, Berry, Groenweg,
Gibson, and Brown (1984) have reported a slight but significant increase
in receptive lexical ability as attested by the scores on the Peabody Picture Vocabulary
Test (PPVT) in a five-year longitudinal study of 31 young adults with standard trisomy
21. Over this period of time, mean PPVT score changed from 56.9, (SD 18.4) to 61.3,
(SD 18.4), a moderate but statistically significant increase that paralleled (and
perhaps was related to) a significant increase in nonverbal mental development as
assessed by the Raven's Progressive Coloured Matrices as well as progress on an
Index of Adaptive Functioning (devised at the University of Calgary, Canada). There
may be, therefore, some modest but continued vocabulary growth in adults with Down
syndrome. The pragmatic and communicative studies reviewed by
Rosenberg and Abbeduto (1993) suggest continued development from childhood
into adolescence and adulthood. But the lack of precise age-related comparisons
in this corpus of studies makes it impossible to establish exactly where in time
the specific developmental changes take place.
Basically the same conclusion can be reached regarding a possible language evolution
from late childhood (say 12-14 years) and adolescence in Down syndrome (and other
intellectually impaired) individuals, using the series of comparative data available
(Bleile and Schwartz,
and Woolnough, 1988; Comblain,
1994; Dodd, 1976;
Fowler, 1988; Fowler, Gelman, and Gleitman,
1994; Lenneberg, 1967;
Rondal, 1978; Rondal
et al., 1981;
Rosenberg and Abbeduto, 1993;
Smith and Stoel-Gammon, 1983;
Stoel-Gammon, 1980; Van
In other words, there is no clear empirical indication at this time that substantial
development takes place beyond 12-14 years in the computational language aspects
of Down syndrome (and other intellectually impaired) individuals whereas there may
be some continued progress with age in lexical referential and pragmatical/communicative
abilities, expressively as well as receptively.
Most interestingly, it is ascertained in the studies of language-wise exceptional
Down syndrome and intellectually impaired subjects (references given above) that
these subjects developed their excellent morphosyntactic and phonological abilities
between approximately 4 and 10 years CA. This attests two things: first, the existence
of a delay in phonological and grammatical development in these subjects approximately
of the same magnitude as those usually observed in typical intellectually impaired
(and Down syndrome) subjects. This delay represents the additional amount of time
needed for moderately and severely intellectually impaired individuals to develop
the cognitive- semantic basis from which lexical and grammatical development may
then proceed. Second, once they have started developing, linguistically exceptional
intellectually impaired subjects proceed relatively quickly in their grammatical
development (over a 4 or 5 year-period as it would seem) but, and this is the crucial
point, within childhood. All in all, the above data are fairly compatible with the
hypothesis of the existence of a critical period for computational language development
in intellectually impaired as well as in non-intellectually impaired children, as
suggested by Lenneberg (1967). As is known,
this hypothesis has found a convincing empirical basis in the work of Curtiss and
associates with Genie, a modern-day "wild child" kept away from social
contact for most of the 13 years of her life (Curtiss,
1977), and in the repeated demonstration (e.g.,
Mayberry, Fisher, and Hatfield, 1983,
Ploog, 1984; Newport, 1984,
that "late" learners of the American Sign Language (ASL, the esoteric
sign system used by deaf people in the United States of America) - i.e., deaf individuals
first exposed to ASL after age 12 - never learn to sign and never develop grammatical
knowledge in ASL as native ASL signers or subjects first exposed to ASL in their
earlier years, even after 30 years of practice.
According to Hurford (1991), the major determinant
for the end point of the critical period (around 12 years) is the evolutive consequence
of the interplay of genetic factors influencing life-history characteristics in
relation to language acquisition. If the ending of the critical period for computational
language development is controlled by genetic factors and is the product of evolution,
as Hurford suggests, there is no reason why intellectually impaired persons (including
those with Down syndrome) should escape it. Regarding phonological and morpho-syntactic
development, it may well be the case that moderately and severely intellectually
impaired individuals are squeezed, so to speak, between two constraining time parameters:
(1) late onset of development (for brain-maturational reasons and because of the
longer time necessary to set a sufficient cognitive-semantic basis from which computational
language can proceed); (2) the ending of the critical period for basic structural
Conceptual and social-communicative aspects of language do not appear to be constrained
in similar ways by biological-time factors. Development may continue in these aspects
for years beyond puberty, at least in some ways; and this seems to be true for intellectually
impaired persons as well. This is compatible with the possibility of a slow continued
growth in MA in Down syndrome people in the third and fourth decades of life (cf.
Berry et al., 1984).
Spelling out the practical implications of the above considerations, one will insist
that every educative effort should be made to help children with Down syndrome to
develop their phonological and morpho-syntactic skills before 12 years or so, for
the benefits of later training become less and less with time beyond this stage.
Regarding vocabulary and the pragmatic and social aspects of language, more developmental
time may be available to the trainers. Of course, this would not be a good idea
not to use maximally the early years for training purposes but further training
beyond 12 years can have some efficacy, and it should probably go on until the mid-adult
Ageing, Alzheimer disease, and the language of individuals with Down syndrome
Normal ageing (i.e., beyond, say, 65 years) - not talking of senility or pathological
ageing such as the effects of Alzheimer disease, Pick disease or other degenerative
diseases - is known to induce physiological and neuropsychological changes that
can affect language and communication. For example, psychomotor performance is slower
in older persons. Respiratory support for speech is less efficient. Changes in laryngeal
functioning contribute to modification of voice pitch (Honjo and Isshiki, 1980). Hearing
problems affect a large proportion of older people (so-called presbyacousis; Willot, 1991). Perception of fast rates of speech,
speech in noise, whispered and higher pitched voices is reduced; resulting, for
instance, in difficulties in communicating on the telephone. Loss of vision determining
loss of visual information can also affect communication.
Cognitive deterioration may take place in selective attention (particularly divided
attention situations). The process of learning and retaining new information becomes
more limited with advancing age. Different types of memory are affected by the ageing
process. There may be a mild decrease in short-term memory (STM) in older subjects
although this varies according to factors such as the complexity of the information
to be recalled (Craik
and Rabinowitz, 1985). A number of studies bearing on the functioning of
working memory (the version of STM in Baddeley's theory; Baddeley, 1990) in older persons suggest that
the mechanism identified by Baddeley under the name of "central executive"
could be particularly affected by the ageing process, hence provide fewer attentional
and (secondary) storing resources. The auditory-verbal and the visuo-spatial stores
could also be reduced as well as their processing speed (Salthouse and Babcock, 1991).
The decline in long-term memory (LTM) capacity in older persons may be more significant.
Differences between younger and older individuals relate to encoding, organizational,
and retrieval factors and strategies (Rankin
and Collins, 1985). Some LTM subsystems resist ageing better than others.
For example, episodic memory (i.e., autobiographical memory; Tulving, 1983) is more age-sensitive than memories
for perceptual representation or semantic memory (i.e., the memory for language
What about language change in the elderly population?
Specific information is still relatively sparse. Grammatically, there is some evidence
that the ability of the elderly to understand complex and/or long sentences may
be reduced. The same situation prevails for grammatical sentences that are ambiguous
and demand processing flexibility (e.g., potentially ambiguous double-object sentences
such as "He showed her baby pictures") (Scholes,
1978), and for sentences containing a temporal subordinate clause headed
by "before" or "after". This is particularly true when the order
of mention in the sentence differs from the order of occurrence of the referred
events (e.g., "He went out after having breakfast", as opposed to "He
had breakfast before going out") (Maxim,
Older people have more difficulty than younger people in extracting information
from spoken texts (Cohen, 1979).
This is obvious when inferential questions are asked about the text (as opposed
to direct questions). It could be that the elderly have particular difficulty with
text inferences when problem solving and complex linguistic analyses have to be
carried out at the same time.
Fewer descriptions of the language that older adults produce are available. Proportions
of dysfluencies are higher than in the speech of younger people (Yairi and Clifton, 1972). However,
these dysfluencies seem to be for the major part hesitant interjections and fillers,
probably attesting the longer time the elderly need to process utterances for production.
Consistent with the indication of a possible organizational difficulty in oral language
output, is Davis' (1979) observation that older
adults use fewer embedded clauses (known to be more demanding of processing resources)
than middle-age groups; an observation not made in written language where more time
is available to monitor complex expression (Obler,
Mildworf, and Albert, 1977).
No particular segmental phonological difficulties are reported in normal ageing.
Older people show changes in single-word processing. They usually are slower on
fluency tasks such as producing names within one semantic category in a period of
time. Given additional time, however, the elderly achieve the same results as younger
The problem that the elderly themselves mention most frequently is increased difficulty
in word retrieval hence the augmented use of semantically indefinite words and third-person
pronouns in discourse with increasing age. A decline in the ability to retrieve
from lexicon is likely in older age. Prevalent among lexical difficulties are those
related to proper nouns (e.g.,
Lovelace and Twohig, 1991). The reasons are not well understood. They may
have to do with the fact that proper nouns refer to individual entities and not
to categories of entities as common nouns do. This drastically reduces the ways
available to activate lexical entries for proper nouns (priming effect).
What about normal ageing in intellectually impaired individuals?
There is no reason not to expect intellectually impaired (including Down syndrome)
persons to present the same ageing characteristics, psychological and otherwise,
and to the same degree and extent, as non-intellectually impaired people. The limited
information available to date on cognitive ageing in individuals with Down syndrome
confirms this indication.
Changes in sensory systems have been acknowledged as common consequences of ageing
in the intellectually impaired population. Some deficits may be particularly common
among ageing people with Down syndrome when compared to non-Down syndrome intellectually
impaired people. Evenhuis, Van Zanten, Borcaar
and Roerdinkholder (1992) have described hearing losses of 20db to over
90db at the speech frequencies (circa 3000Hz) in 33 out of 35 Dutch adults with
Down syndrome aged 35-62 years. Cochlea losses were noted in 69% of the cases. Evenhuis
et al. suggest that hearing loss should be considered as a contributing factor in
the social and mental decline of middle-age persons with Down syndrome. Ocular findings
from 30 individuals with Down syndrome aged 21-72 years are reported by
Hestnes, Sand, and Tostad (1991). Strabismus, cataract, and visual losses
were found to affect almost all subjects to various degrees.
Language studies of normally ageing individuals with Down syndrome are almost non-existent.
In the only systematic study that I was able to locate,
Young and Kramer (1991) investigated age differences in 60 adults with Down
syndrome (aged 22-67 years), reportedly with no hearing impairment. Older subjects
were less likely to attend to auditory stimuli, had poorer word discrimination,
and were less able to understand the meaning of spoken language. Expectedly, these
older subjects had more difficulty in following verbal directions.
It is possible to be more specific, at least predictively, in extrapolating from
the language literature on normal ageing. Table 4 summarises these predictions,
of course pending empirical verification.
Table 4. Additional language problems in ageing persons
with Down syndrome.
Slower productive and receptive language processing.
Less efficient respiratory support for speech.
Aggravated hearing problems; hence reduced attention to auditory stimuli, particular
difficulties in perceiving whispered speech, speech in noisy conditions, and in
communicating on the telephone.
Additional difficulties in linguistic analysis and information extraction from spoken
Additional problems in following verbal directions.
Augmented rates of dysfluencies (particularly hesitation pauses, interjections,
Additional difficulties in organizing spoken discourse.
Reduced word fluency.
Increased difficulty in word discrimination, and in retrieving common and proper
Language therapy intervention with the non-intellectually impaired elderly (e.g.,
Maxim and Bryan, 1994)
could be adapted to the ageing person with Down syndrome. It could help reduce their
processing difficulties, if only partially. Also the social environment of ageing
intellectually impaired persons can be adapted relatively easily to the language
limitations in these people (e.g., speaking more slowly and loudly to the older
person with Down syndrome, using shorter and formally simpler utterances, allowing
them additional time to process incoming language and to respond verbally).
Unfortunately, for a number of older persons with Down syndrome, there is more to
ageing than physiological ageing. They may develop a debilitating degenerative disease
known as Alzheimer disease (AZ), also occurring in older non-intellectually impaired
and non-Down syndrome intellectually impaired people but with a lower incidence.
In Alzheimer disease, the brain neurons develop neurofibrillary tangles i.e. flame-shape
alterations composed mainly of condensed cytoskeletal proteins. Another protein,
8/A4amyloid is deposited in large amounts in the form of senile or neuritic plaques,
and around blood vessels causing reduced blood flow (amyloid angiopathy). The gradual
accumulation of these changes plus neuronal loss, alteration of motor nuclei of
brain stem, and reduction of neurotransmitters, render the affected parts of the
brain less and less able to function properly, hence the functional Alzheimer disease
The particular cytogenetic association between Down syndrome and Alzheimer disease
is beginning to be better understood. There are several suspected genetic causes
of Alzheimer disease in non-Down syndrome people, possibly involving several chromosomes,
which we will not consider here (see, for example, several contributions to the
edited book by Berg,
Karlinsky, and Holland, 1993). In the case of trisomy 21, one possible partial
explanation (there are alternative ones currently under scrutiny) is that the amyloid
precursor protein (APP) gene resides on chromosome 21 (in the proximal part of the
long arm of chromosome 21) (Goldgaber,
Lerman, McBride, Saffiotti, and Gajdusek, 1987;
Hyman, 1992). Indeed Alzheimer disease-like pathology has been demonstrated
with animals transgenic for a fragment of the APP (Kawabata,
Higgins, and Gordon, 1991). Neurofibrillary tangle-like structures were
also reported in animals whose brains had been injected with 8/A4 amyloid protein
itself (Kowall, Beal,
Busciglio, Duffy, and Yankner, 1991). In trisomy 21, it is possible that
overproduction of the APP leads to alterations in brain morphology. Neuropathological
examination of individuals with Down syndrome who have died before the fifth decade
show a few neurofibrillary tangles and neuritic plaques in some areas and layers
of the brain (not to be considered here). The continued accumulation of these changes
results in brain dysfunction and consequently cognitive decline by the 50s or the
60s (Hyman, 1992). The brain changes involved are
the same biochemically as those characterizing Alzheimer disease in older non-intellectually
It is estimated that in non-intellectually impaired persons, approximately 3% will
develop Alzheimer disease before or around 60 years. The incidence increases to
about 20% beyond 75 years (e.g.,
Evans et al., 1989 _ it should be noted, however, that this figure may encompass
degenerative diseases other than Alzheimer disease). These figures may probably
be transposed (and perhaps augmented) 15 or 20 years earlier in life for persons
with Down syndrome. Most importantly, in Down syndrome, there seems to be a 15-year
delay between the first major alterations at brain level and the behavioural manifestations
of cognitive decline. In non-intellectually impaired people, the corresponding delay
is only approximately 7 years. The reason for this difference is not known. This
period, particularly in Down syndrome, offers time space for psychopharmacological
and behavioural interventions with the prospect of slowing down the progress of
the disease. It is possible that cognitive decline accelerates only from the time
when alterations become so extensive as to overwhelm the functional compensatory
mechanisms of the brain.
At the present time, there is virtually no systematic study of cognitive and linguistic
decline in individuals with Down syndrome with clearly diagnosed Alzheimer disease.
Suggestions can be made on what to expect from the beginning literature on the particular
language problems of non-intellectually impaired persons with Alzheimer disease.
It would seem that language is compromised at all stages in Alzheimer disease but
that there is enormous variation in deficits among individuals. Despite such a large
variation, general lines of major symptomatology may be traced. Language changes
in Alzheimer disease are most apparent at the semantic level (particularly, reduction
of available vocabulary and breakdown of semantical associations) (Martin, 1987). Difficulty in word finding is one
of the most noticeable feature of Alzheimer disease. Auditory comprehension of words
also shows deficits, as well as the comprehension of semantic complexity in sentences
and paragraphs (Hart, 1988).
The quality of discourse, cohesion, and, in short, the whole pragmatics of language
are usually found to be gravely deteriorating (see
Maxim and Bryan, 1994, for a review).
Most interesting is the repeated observation that the computational aspects of language
(and particularly the grammatical structures) are largely spared in Alzheimer disease.
They may be disturbed because of the breakdown in the language conceptual aspects,
but no or only little as the primary effect of Alzheimer disease pathology (Appel, Kertesz, and Fishman,
1982). For example, Kempler,
Curtiss, and Jackson (1987) observed a normal range and frequency of
syntactic constructions (but poor lexical use) in the spontaneous speech as well
as in writing with a group of 20 non-intellectually impaired patients with Alzheimer
disease. These data are suggestive of a dissociation between semantic and syntactic
levels in Alzheimer disease reflecting the modularity characteristics of the functional
organisation of language and the fact that organic deterioration in Alzheimer disease
has a predilection for certain brain sites (at least at the earlier stages) leaving
others untouched (e.g.. those underlying syntactic processing).
Table 5 briefly summarizes the probable implications of the above observations from
non-intellectually impaired Alzheimer disease patients to Alzheimer disease in individuals
with Down syndrome.
Table 5. Predicted language profile associated with Alzheimer disease in persons
with Down syndrome
Major dissociation between language computational (phonology and
morpho-syntax) and language conceptual and social aspects (lexicon,
semantics, pragmatics, discourse organisation and comprehension): the former aspects
(underdeveloped in persons with Down syndrome) being little touched directly
(they may be affected indirectly as a result of the cognitive-semantic breakdown),
whereas the latter aspects will be found deteriorating to an extent varying from
person to person.
Concluding, we are searching and gradually building a life-span psycholinguistics
and neurolinguistics of Down syndrome (Rondal, 1988) that will put us in a better
position to advance educational intervention and management of persons with Down
syndrome and make their effects more durable and generalisable.
Paper first presented at
The International Conference on Language and Cognitive Development in Individuals
with Down Syndrome September 1994, University of Portsmouth, Portsmouth, United
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DSE's Reading and Language Intervention for Children with Down Syndrome (RLI) is an evidence-based programme designed to teach reading and language skills to children with Down syndrome.
RLI incorporates best practice in structured activities delivered in fast-paced daily teaching sessions. It was evaluated in a randomised controlled trial and found to improve rates of progress compared to ordinary teaching.
Find out more...