Down syndrome phonology: Developmental patterns and intervention strategies
This paper describes phonological development in children with Down syndrome paying particular attention to underlying deficits and intervention strategies. The first section provides an overview of factors believed to influence phonological development in this population. The second section describes four aspects of Down syndrome phonology: (1) the prelinguistic stage; (2) the transition to speech; (3) the phonology of the single words; and (4) phonological characteristics of conversational speech with a focus on intelligibility. Intervention strategies associated with each aspect are also presented. Children with Down syndrome are slow to acquire the phonological system of their mother tongue. In spite of normal or nearly normal prelinguistic development, these children are delayed in the use of meaningful speech and slow to acquire a productive vocabulary. In some cases their speech remains unintelligible throughout childhood and adolescence, making it difficult to communicate with those around them. The purpose of this paper is to summarize research on phonological development of children with Down syndrome with attention to underlying deficits and to the speech characteristics of prelinguistic vocalisations as well as words and conversation. Current views on intervention are also described.
Stoel-Gammon C. Down syndrome phonology: Developmental patterns and intervention strategies. Down Syndrome Research and Practice. 2001;7(3);93-100.
Factors affecting phonological acquisition
The phonological systems of children with Down syndrome are influenced by
a variety of factors that can create difficulties perceiving and producing
speech. In addition to the cognitive deficit that is the primary marker
of the syndrome, hearing loss and differences in anatomy and physiology
are contributing factors. Input may also be implicated. The precise influence
of each factor is difficult to determine and may vary from one child to
another. In conjunction, however, these factors have deleterious effects
on speech and language development.
Infants and children with Down syndrome often suffer from mild-to-moderate
hearing loss. Downs (1980) reported that
78% of the children she tested were found to have "hearing problems" in
one or both ears when criteria for a "problem" was a 15 dB loss. Of the
children with a hearing problem, 65% displayed significant levels of loss
in both ears; 54% evidenced conductive loss; 16% had sensorineural loss
in one or both ears; and 8% displayed mixed losses. It was once believed
that hearing loss in the mild-to-moderate range had little effect on language
acquisition; however, research on otitis media in infants has shown
that losses of this magnitude can negatively affect speech and language
& Finitzo, 1990;
Schwartz, Gravel, & Ruben, 1999; Nittrouer,
1996; Roberts, 1997;
Wallace, Gravel, McCarton, & Ruben, 1988). Given the other deficits
faced by children with Down syndrome, it is likely that recurrent hearing
loss compromises their language learning environment and that greater degrees
of hearing loss and/or extended periods of middle ear disease will be associated
with poorer outcomes on speech and language measures. In her review of language
among children and adolescents with Down syndrome, Chapman (1997)
notes that much of the variation in communicative abilities can be better
understood if hearing status is taken into account.
In terms of intervention related to hearing status, the needs are clear:
infants and children with Down syndrome will benefit from an aggressive
treatment for hearing loss associated with middle ear pathology. Balkany
(1980) identified three goals of such
treatment: (1) normalization of hearing through insertion of tympanostomy
tubes and, in some cases, fitting of hearing aids; (2) interruption of the
cycle of recurrent otitis media with effusion through use of prophylactic
drugs; and (3) prevention of chronic ear disease through adequate otologic
care. In addition, Yarter (1980) suggested
that infants and young children also receive an auditory training program
concurrently with their program of speech therapy.
Differences in anatomy and physiology
Individuals with Down syndrome have skeletal and muscular systems that differ
from those individuals without Down syndrome (Leddy,
1999; Miller & Leddy,
1998). For oral structures, the skeletal system is characterized by
absent or deficient bone growth, a smaller oral cavity, and more posterior
tongue carriage; the muscular system is characterized by absent and extra
muscles in the facial region and a large muscular tongue. These differences
in structure and in tongue size influence the production of lingual consonants.
Furthermore, weak facial muscles limit lip movement, thus affecting production
of labial consonants and rounded vowels. General hypotonicity affects lip
and tongue movements involved in all aspects of speech production. Any one
of these factors is likely to influence motor movements associated with
speech, and negatively impact the articulatory and phonatory abilities of
children with Down syndrome.
The nervous system of individuals with Down syndrome also has distinctive
characteristics including anatomical differences in the central and peripheral
nervous system, reduced brain size and weight, smaller and fewer sulci,
narrower superior temporal gyrus, fewer cortical neurons, decreased neuronal
density, delayed neuronal myelination; abnormal dendrite structures; and
altered cellular membranes (Leddy, 1999;
Miller & Leddy, 1998;
Rast & Harris, 1985;
Yarter, 1980). It is hypothesised that
these differences are associated with disruptions in the accuracy, speed,
consistency and economy of speech movements.
The influence of anatomical and physiological characteristics on speech
development of children with Down syndrome was examined by Miller and colleagues
Miolo, Sedey, Pierce, & Rosin, 1989). Using Robbins and Klee's protocol
(1987) to assess the speech
motor abilities of 43 children with Down syndrome, the researchers found
a high correlation between speech motor function and the number of different
words produced by children with Down syndrome in a spontaneous speech sample.
Specifically, the speech function scores obtained at the first data collection
session (when the children were 18-60 months of age) accounted for nearly
80% of the variance in predicting the number of different words in samples
collected approximately 5 months later. The researchers concluded that speech
motor function and phonetic inventory were the best speech predictors of
vocabulary diversity 18 months later. As was the case with hearing status,
it appears that variation in speech and language skills of children with
Down syndrome can be attributed to their speech motor abilities which, in
turn, are related to anatomical and physiological characteristics.
In terms of intervention in this domain, Yarter (1980)
suggested that techniques for improving speech-motor deficits related to
hypotonicity and possible hyposensitivity of the lip should be initiated
in the first year of life and advocated lip stimulation and exercises designed
to strengthen the sucking response through use of a straw. Kumin, Councill
and Goodman (1994)
suggested strengthening the orofacial musculature through a program of lip
massage, and bubble and whistle blowing for young children. The most controversial
intervention in this domain is surgery for tongue reduction. Parsons, Iacono
and Rozner (1987)
report the results of a study in which 18 children with Down syndrome underwent
tongue-reduction surgery as a means of increasing articulatory proficiency.
The children's articulatory skills were assessed pre- and post-operatively,
and at a 6-month follow-up; no significant differences in the number of
articulation errors were found. In addition, the articulation scores of
the children undergoing the surgery were not significantly different than
the scores of a non-surgery group of children with Down syndrome. In spite
of the lack of change in articulatory skills for either group, parents of
children in both groups claimed that their children's speech had improved
at the 6-month follow-up assessment.
Language learning environment
A third factor that may affect phonological development of children with
Down syndrome is the nature of linguistic input they receive. Current theory
holds that language acquisition is the result of a process of social interaction
involving shared activities, and that the rate and quality of caregivers'
language play key roles in language acquisition (Warren
& Yoder, 1997). Research shows that vocal and verbal interactions between
caregivers and children with Down syndrome differ from interactions involving
typically developing children in a number of respects. For the most part,
findings show that adult input is less well suited to the vocal and verbal
abilities of children with Down syndrome (Lynch
& Eilers, 1991; Miller, 1987).
Differences include more "vocal clashing" in "proto-conversations" of infancy,
suggesting that the rhythm of turn-taking exchanges is disrupted (Berger
& Cunningham, 1983); maternal speech that is produced more rapidly and
includes a higher proportion of nouns, shorter utterances, more imperatives,
and more grammatically incomplete sentences (Buckholt,
Rutherford, & Goldberg, 1978;
& Turnure, 1974); and mother-child interactions that are primarily mother-directed
& Mervis, 1985). Although these findings suggest that the input to children
with Down syndrome may be less than optimal in terms of creating an enriched
environment for learning to talk, Rosenberg and Abbeduto (1993)
note that the majority of investigations of input to children with learning
disabilities are plagued by methodological flaws. In particular, they find
little evidence of a causal relationship between features of adult input
Two studies have specifically examined phonological characteristics of speech
to infants and toddlers with Down syndrome. An investigation by Velleman,
Mangipudi and Locke (1989)
reported that, compared with mothers of typically developing infants and
toddlers, the mothers of children with Down syndrome produced significantly
fewer phonetically contingent responses to their children's utterances (i.e.,
responses that reproduced the segmental and/or prosodic characteristics
of the child's vocalization). This finding takes on special significance
in light of an earlier investigation showing that mothers' use of sound
expansions and imitations in speech to their 17-month-old infants with Down
syndrome (i.e., phonological modelling) was correlated positively with the
children's expressive language at 3 years of age (L.
Smith & von Tetzchner, 1986;
Smith, von Tetzchner & Michalson, 1988). If L. Smith's finding about
phonological modelling is replicated in other investigations, parents and
caregivers should be encouraged to increase this type of input to their
infants and toddlers with Down syndrome.
Prelinguistic vocal development
Investigations of prespeech development suggest that infants with Down syndrome
are nearly typical in this domain. Both cross-sectional and longitudinal
studies using various measures and analysis techniques have documented strong
similarities in the amount of vocalization produced; in the developmental
timetable, particularly age at onset of canonical babble; and in the characteristics
of consonants and vowels occurring in canonical babble (Dodd,
1972; Oller & Seibert,
1988; B.L. Smith
& Oller, 1981;
B.L. Smith & Stoel-Gammon
Steffens, Oller, Lynch & Urbano, 1992)
Although the majority of investigations have shown no differences between
prelinguistic development of infants with Down syndrome and their non-Down
syndrome peers, Lynch and colleagues (Lynch,
Oller, Steffens, Levine, Basinger, & Umbel, 1995) reported that the
average age of onset of canonical babbling among the infants with Down syndrome
was about 9 months, approximately two months later than the age for the
typically developing infants, and that the proportional occurrence of canonical
babbling was less stable for the infants with Down syndrome. Because hypotonicity
and delays in motor development are characteristic of Down syndrome, the
relative instability in canonical babbling may be a consequence of deficits
in the motor domain. These findings notwithstanding, one can conclude that
Down syndrome appears to have relatively little effect on prelinguistic
vocal development. In large measure, developmental patterns are within typical
range although the babbling period for infants with Down syndrome is much
longer, often extending through the second year of life.
The transition to speech
According to the typical developmental timetable, children's first words
generally appear around the end of the first year and overlap with canonical
babble for a period of 6-8 months. In a longitudinal study of typically
developing infants, Robb, Bauer, and Tyler (1994)
reported that when their subjects had a productive vocabulary of about 10
different words, the proportion of words and babble in their spontaneous
productions was roughly equal. When the productive vocabulary reached 50
words, at around 18 months of age, the ratio of words to babble was about
three to one.
During the transition to speech, the phonetic characteristics of babble
and speech are highly similar (Locke, 1983;
Stoel-Gammon, 1998). Specifically,
the types of consonants that occur most frequently in late babbling, namely,
stops, nasals and glides, also predominate in early word productions, while
the consonants that are infrequent in babble, liquids, fricatives, and affricates,
are precisely those that appear later in the acquisition of meaningful speech
(Stoel-Gammon, 1985). Moreover, the
consonant-vowel syllable structure which is characteristic of the canonical
babbling period is also the most frequent syllabic type in early word productions.
Thus, among the typically developing population, babbling and early speech
share the same basic phonetic properties in terms of sound types and syllable
Not only do babble and early words share phonetic characteristics during
the transition to speech, there is a growing body of evidence linking prelinguistic
vocal development with general speech and language skills throughout early
childhood (Stoel-Gammon, 1992,
1998). In general, increased use
of complex babble in the prelinguistic period is linked to better performance
on the speech and language measures after the onset of speech and in the
years that follow. These findings suggest that babbling serves as a foundation
for the acquisition of speech and language; Stoel-Gammon (1998)
hypothesised that infants who produce more babble, particularly more canonical
utterances with a variety of consonants and vowels, have amassed a greater
arsenal of "building blocks" that can be recruited for the production of
a variety of words.
Given that prelinguistic vocal development of infants with Down syndrome
is typical in most respects, and that prelinguistic development is closely
linked to early linguistic development, one might expect that early language
acquisition among infants with Down syndrome would be nearly typical. This,
however, is not the case. Most children with Down syndrome exhibit a substantial
delay in the appearance of first words, in spite of their normal babbling
patterns. Stray-Gunderson (1986),
for example, noted extreme variability in the age at which children with
Down syndrome produced their first words. Some children produced words as
early as 9 months (chronological age), within the range for children with
typical development, whereas for others, the first words did not appear
until the age of 7 years (chronological age). The observed delays in onset
of meaningful speech and the wide disparity in the age of onset are presumably
associated with a number of factors described in the previous section.
Information regarding the transition from babble to speech in infants with
Down syndrome comes from work by B.L. Smith (1977;
1984) whose longitudinal data, collected
in a laboratory setting, showed that the average age of onset of meaningful
speech (i.e. occurrence of productions judged to be recognizable words)
was 14 months for the typically developing infants and 21 months for the
infants with Down syndrome, a difference of 7 months. Moreover, at 14 months
approximately 13% of the utterances of the typically developing group were
judged to be attempts at meaningful speech; at 18 months of age, about half
the utterances produced by this group were classified as meaningful. By
comparison, only 2% of the utterances produced by 21-month-old infants with
Down syndrome were judged to be meaningful (by experimenters and/or parents),
and at 30 months the proportion of meaningful utterances remained under
The findings of Buckley (2000) extend
our understanding of lexical acquisition in Down syndrome children. Her
data show that vocabulary growth is quite slow. At 24 months of age, the
average productive vocabulary was 28 words (compared with 250 for a typically
developing child). At 3 years, the mean vocabulary was 116 words, rising
to 248 words at 4 years, to 272 words at 5 years, and 330 words at 6 years,
an age at which the child with typical development has a productive vocabulary
of several thousand words. In terms of early lexical acquisition, the child
with typical development achieves a productive vocabulary of about 250 words
at two years of age; among children with Down syndrome, this milestone is
not attained until two years later, at the age of four years.
Taken together, the research by Buckley and B.L. Smith indicates that the
onset of meaningful speech is significantly delayed in the infants with
Down syndrome and that after the appearance of words, growth of productive
vocabulary is exceedingly slow. Other investigations of lexical acquisition
in children with Down syndrome have shown that even when the Down syndrome
group is matched to a typically developing control group on mental (rather
than chronological) age, lexical acquisition in children with Down syndrome
is delayed (Chapman, 1997).
In terms of intervention strategies appropriate for the transition to speech,
the focus should be on supporting lexical acquisition by increasing the
child's awareness of the use of sounds as meaningful elements in communication.
Specifically, caregivers (i.e. parents, child-care workers, teachers) should
encourage the use of words by producing phonetically contingent responses
to non-meaningful vocalisations; for example, caregivers might repeat the
child's non meaningful utterance [ba] and link it to the phonetically similar
word "ball", thus increasing the likelihood of [ba] being used as a meaningful
utterance. In addition, caregivers can play "sound games" to make infants
and toddlers aware of speech sounds and of sound-meaning relationships with
the goal of increasing the child's repertoire of speech sounds and syllable
The phonology of single words
In general, word productions of children with Down syndrome have the same
phonological characteristics as those of children with typical development
(Dodd & Leahy, 1989;
Rosenberg & Abbeduto,
1993). In particular, stop, nasal and glide consonants tend to be produced
accurately while fricatives, affricates and liquids are often in error (Bleile
& Schwarz, 1984; B.L. Smith, 1984;
1981). Phonological process analyses
have also highlighted similarities between children with Down syndrome and
those with typical development with the following patterns occurring frequently:
(1) consonant clusters are produced as singleton consonants; (2) word-final
consonants are omitted; (3) target fricatives and affricates are produced
as stops; (4) aspirated voiceless stops in initial position are deaspirated;
(5) word-initial liquids are produced as glides and word-final liquids are
produced as vowels or are omitted; and (6) word-final voiced obstruents
are devoiced (Van Borsel, 1996;
& Goodman, 1994; Mackay
& Hodson, 1982;
B.L. Smith & Stoel-Gammon,
1983; Stoel-Gammon, 1980,
As might be expected, however, phonological acquisition in children with
Down syndrome proceeds more slowly than in their cognitively typical peers.
B.L. Smith and Stoel-Gammon (1983)
calculated the rate of suppression of four phonological processes in their
longitudinal study. They reported that, in the children developing typically,
average percentage of occurrence of the processes declined from 63% at 18-24
months to 25% at 30-36 months, representing a change of about 38% in a 12-month
period. By comparison, the average percentage of occurrence of the same
processes in the speech of children with Down syndrome was 61% when the
children were 3-years-old, declining to 40% at the age of 6 years, an average
change per year of 6% compared with 38% for the children with typical development.
Even when the children with Down syndrome achieve a mental age of 7 or 8
years, errors characteristic of younger children are still present. Errors
documented for young children with Down syndrome tend to persist through
adolescence and even adulthood (Shriberg
& Widder, 1990;
Sommers, Reinhart & Sistrunk, 1988;
Sommers, Patterson & Wildgen, 1988).
In addition to persisting longer, error patterns for children with Down
syndrome are also more variable than for children with typical development.
Dodd (1976) compared the phonological
systems of three groups of children matched for mental age: typically developing,
children with severe learning difficulties and children with Down syndrome.
Although there were no statistical differences in the number and type of
phonological errors occurring in spontaneous and imitated productions of
the typically developing children and those with severe learning difficulties,
the performance of children with Down syndrome exhibited several differences:
they made a greater number of phonological errors in their productions;
their errors were more inconsistent; and a greater proportion of their errors
could not be described by a set of common phonological processes. Furthermore,
these children made fewer errors in imitated than in spontaneous productions
than children in the other groups. Dodd (1975;
1976) suggested that these findings provide
evidence of a difficulty in motor speech programming in children with Down
syndrome, perhaps related to a general deficit in their motor abilities.
Stoel-Gammon (1981) also reported
greater variability in errors produced by Down syndrome participants. She
noted, for example, that children with typical development move from incorrect
to correct phoneme production in a linear fashion with a small set of substitution
types. In contrast, among children with Down syndrome, there was a greater
range of substitution types and these varied from one word to another.
In terms of intervention for single-word productions, most programs focus
on increasing the phonetic repertoire and reducing the number of errors,
using therapy techniques similar to those for children with phonological
delay or disorder. Of particular interest is a study by Cholmain (1994)
who described a therapy program for young children with Down syndrome (chronological
age 4;1-5;6) with unintelligible speech, and language ages ranging from
1;4 to 2;10. The program provided children with "simple uncluttered examples
of the organisation of the sounds in the language in order to encourage
them to construe the phonological system" (p. 16). Based on the therapy
principles advocated by Hodson and Paden (1983),
key elements of the program included listening and production practice focused
on particular phonemes and phonological processes, with therapy occurring
in the clinic and at home. In spite of the low language ages of the children
involved in the study, results showed change in their phonological systems
within the first two weeks of beginning therapy despite minimal change in
the previous 3-12 months. Most notably, there were dramatic increases in
the measure of Percent Consonant Correct, with pre-therapy figures ranging
from 3-38% and post-therapy figures (6-14 weeks later) ranging from 19-88%.
In addition, there were marked improvements in the children's use of grammatical
forms. The author concluded that the therapy approach allowed the children
to restructure their sounds systems and proceed in syntax development.
Another type of therapy program focused on the variability of word productions
by children with Down syndrome (Dodd
& Leahy, 1989;
& Woodyatt, 1994). This approach differed from traditional intervention
programs in two ways: the unit of treatment was whole words rather than
phonemes or phonological processes and parents served as the agents of therapy.
Parents were instructed to accept only one pronunciation for a set of words
individually selected for their child. Acceptable pronunciations did not
necessarily need to be correct; however, the words with errors had to be
consistently produced and errors had to be "developmental" rather than "deviant."
Results indicated that, over the 13 week program, the four children in the
study showed "exceptional improvement" in the number of consonants produced
correctly. Moreover, the mean proportion of "deviant" errors reduced from
around 70% to 41% during this period. Although the numbers of participants
in these studies was relatively limited, the findings are promising.
At the age four years, the speech of most children with typical development
is fully intelligible, even though their phonological systems are not yet
complete (Coplan & Gleason,
1988). By comparison, the speech of some individuals with Down syndrome
tends to be unintelligible throughout their lives even though their mental
age may exceed four years (Kumin 1994;
Pueschel & Hopman, 1993;
Rosin, Swift, Bless & Vetter, 1988;
Shriberg & Widder, 1990).
Long-standing difficulties with intelligibility can presumably be attributed
to phonological patterns associated with Down syndrome.
Two studies have examined parents' perceptions of the speech and language
skills of their children with Down syndrome. Kumin's (1994)
analysis of 937 parent questionnaires revealed that nearly 60% of parents
reported that their children (aged birth to 40+ years) "frequently" had
difficulty being understood. An additional 37% reported that their children
"sometimes" had difficulty being understood. When asked to indicate which
speech skills were particularly troublesome for their children, articulation
was ranked highest with 80% of the parents noting difficulties in this area.
Pueschel and Hopman (1993)
also used a questionnaire to gain information on the parents' views of their
children's speech and language skills. Although parents reported that their
children were generally capable of making themselves understood, 71-94%
of parents of children aged 4-21 years noted that their offspring had problems
with articulation. It is likely that the perceived levels of unintelligibility
are associated with variable phoneme production noted in the previous section,
a factor which increases the difficulty for identifying a target word. In
addition, atypical prosodic patterns, as reported by Shriberg and Widder
(1990), are often
associated with decrease in speech intelligibility.
There are few intervention programs for children with Down syndrome aimed
specifically at increasing intelligibility (but see
Swift & Rosin, 1990), and
treatment for language, at least in the United States, is often part of
more general educational programs designed to teach "life skills". The ultimate
goal of such programs is to allow individuals with learning disabilities
to live independently and work in the community. In the domain of speech
and language, efforts are often directed toward increasing the functional
communication skills necessary for social interactions and vocational training
with little emphasis on phonology skills per se.
Although learning "life skills" is important, the emphasis on functional
communication at the expense of more focused phonological therapy is open
to question. Shriberg and Widder (1990)
argue that in spite of the slow progress of children with Down syndrome
and the limited resources of speech therapists and special education teachers,
articulation therapy should remain as a high priority throughout childhood
and adolescence. These authors note that improving the segmental and suprasegmental
aspects of speech would increase intelligibility, which in turn would benefit
social and vocational elements of individuals with learning difficulties.
In a similar vein, Fowler (1995) recommends
to parents that they invest in speech therapy stating that it "will provide
your child with a greater sense of power to be understood." (p. 129). In
closing, it should be remembered that speech therapy need not be the exclusive
domain of therapists; parents, caregivers and educators can also be trained
to serve as agents of therapy thereby broadening the contexts in which therapy
occurs and increasing the amount of intervention a child receives. In terms
of phonology, long-term intervention, first for the transition to words,
then for single word articulation skills, and finally for conversational
speech, is to be encouraged.
Carol Stoel-Gammon • Department of Speech and Hearing Sciences, University
of Washington, 1417 N.E. 42nd Street, Seattle, WA 98105-6246, USA • Fax:
+1-206-543-1093 • E-mail: email@example.com
- Balkany, T. J. (1980). Otologic
aspects of Down's syndrome. Seminars in Speech, Language and Hearing,
- Berger, J., & Cunningham,
C. C. (1983). Development of early vocal behaviors and interactions
in Down's syndrome and nonhandicapped infant-mother pairs. Developmental
Psychology, 19, 322-331.
- Bleile, K., & Schwarz,
I. (1984). Three perspectives on the speech of children with Down syndrome.
Journal of Communication Disorders, 17, 87-94.
Buckholt, J. A., Rutherford, R. B., & Goldberg, K. E. (1978). Verbal
and nonverbal interaction of mothers with their Down's syndrome and nonretarded
infants. American Journal of Mental Deficiency, 82, 337-343.
- Buckley, S. (2000) Teaching reading
to develop speech and language. Presented at the 3rd International Conference
on Language and Cognition in Down Syndrome, Portsmouth, UK, September
- Buium, N.,
Rynders, J., & Turnure, J. (1974). Early maternal linguistic environment
of normal and non-normal language-learning children. American Journal
of Mental Deficiency, 79, 52-58.
C., & Mervis, C. B. (1985). Maternal speech to prelinguistic children
with Down syndrome. American Journal of Mental Deficiency, 89,
- Chapman, R. S. (1997). Language
development in children and adolescents with Down syndrome. Mental Retardation
and Developmental Disabilities Research Reviews, 3(4), 307-312..
- Cholmain, C. N. (1994). Working
on phonology with young children with Down syndrome. Journal of Clinical
Speech and Language Studies, 1, 14-35.
- Coplan, J., & Gleason,
J. (1988). Unclear speech: Recognition and significance of unintelligible
speech in preschool children. Pediatrics, 82, 447-452.
- Dodd, B. J. (1972). Comparison of babbling
patterns in normal and Down-syndrome infants. Journal of Mental Deficiency
Research, 16, 35-40.
- Dodd, B. J. (1975). Recognition and
reproduction of words by Down's syndrome and non-Down's syndrome retarded
children. American Journal of Mental Deficiency, 80, 306-311.
- Dodd, B. J. (1976). A comparison of
the phonological systems of mental age matched normal, severely abnormal
and Down's syndrome children. British Journal of Disorders of Communication,
- Dodd, B. J., & Leahy,
P. (1989). Phonological disorders and mental handicap. In M. Beveridge,
G. Conti-Ramsden, & I. Leudar (Eds.), Language and Communication in
Mentally Handicapped People (pp. 33-56). London: Chapman and Hall.
- Dodd, B.,
McCormack, P. & Woodyatt, G. (1994). Evaluation of an intervention program:
Relation between children's phonology and parents' communicative behavior.
American Journal of Mental Retardation, 98(5), 632-645.
- Downs, M. P. (1980). The hearing of
Down's individuals. Seminars in Speech, Language and Hearing, 1,
- Fowler, A. (1995). Linguistic variability
in persons with Down syndrome: Research and implications. In L. Nadel &
D. Rosenthal (Eds.), Down Syndrome: Living and Learning in the Community
(pp. 121-131). New York: Wiley-Liss Inc.
- Friel-Patti, S. &
Finitzo, T. (1990). Language learning in a prospective study of otitis
media with effusion in the first tow years of life. Journal of Speech,
Language, and Hearing Research, 33, 188-194.
- Hodson, B. W. & Paden,
E.P. (1983). Targeting Intelligible Speech. San Diego: College
- Kumin, L. (1994). Intelligibility of
speech in children with Down syndrome in natural settings: Parents' perspective.
Perceptual and Motor Skills, 78, 307-313.
- Kumin, L.,
Councill, C., & Goodman, M. (1994). A longitudinal study of the emergence
of phonemes in children with Down syndrome. Journal of Communication
Disorders, 27, 265-275.
- Leddy, M. (1999). The biological bases
of speech in people with Down syndrome. In J. F. Miller, M. Leddy, & L.
A. Leavitt (Eds.), Improving the Communication of People with Down Syndrome
(pp. 61-80). Baltimore: Paul H. Brookes.
- Locke, J. L. (1983). Phonological
Acquisition and Change. New York: Academic Press.
- Lynch, M., & Eilers,
R. E. (1991). Perspectives on early language from typical development
and Down syndrome. In N. W. Bray (Ed.), International Review of Research
on Mental Retardation: Vol. 17 (pp. 55-90). New York: Academic Press.
Lynch, M. P., Oller, D. K., Steffens, M. L., Levine, S. L., Basinger, D.
L., & Umbel, V. M. (1995). Development of speech-like vocalizations
in infants with Down syndrome. American Journal of Mental Retardation,
- Mackay, L., & Hodson,
B. (1982). Phonological process identification of misarticulations of
mentally retarded children. Journal of Communication Disorders, 15, 243-250.
- Miller, J. F. (1987). Language and
communication characteristics of children with Down syndrome. In S. Pueschel,
C. Tinghey, J. Rynders, A. Crocker, & C. Crutcher (Eds.), New Perspectives
on Down Syndrome (pp. 233-262). Baltimore: Brookes Publishing.
- Miller, J. F. (1988). The developmental
asynchrony of language development in children with Down syndrome. In L.
Nadel (Ed.), The Psychobiology of Down Syndrome (pp. 167-198).
Cambridge, MA: MIT Press.
- Miller, J. F., & Leddy,
M. (1998) Down syndrome: the impact of speech production on language
development. In R. Paul (Ed.), Communication and Language Intervention:
Vol. 8. Exploring the Speech-Language Connection (pp. 163-177). Baltimore:
Paul H. Brookes.
Miller, J.F., Miolo, G., Sedey, A., Pierce, K., & Rosin, M (1989) Predicting
lexical growth in children with Down syndrome. Poster presented at the
Annual Meeting of the American Speech-Language-Hearing Association,
St. Louis, MO.
- Mody, M., Schwarz, R., Gravel, J., & Ruben, R. (1999).
Speech, Language and Hearing Research, 42, 1069-1079.
- Nittrouer, S. (1996). The relationship
between speech perception and phonemic awareness: Evidence from low SES
children and children with chronic OM. Journal of Speech and Hearing
Research, 39, 1059-1070.
- Oller, D.K. & Seibert,
J.M. (1988). Babbling of prelinguistic mentally retarded children.
American Journal on Mental Retardation, 92, 369-375.
C. L., Iacono, T. A., & Rozner, L. (1987). Effect of tongue reduction
on articulation in children with Down syndrome. American Journal of
Mental Deficiency, 91, 328-332.
- Pueschel, S., & Hopman,
M. (1993). Speech and language abilities of children with Down syndrome.
In A. P. Kaiser & D.B. Gray (Eds.), Enhancing Children's Communication
(pp. 335-362). Baltimore: Paul H. Brookes.
- Rast, M. M., & Harris,
S. R. (1985). Motor control in infants with Down syndrome. Developmental
Medicine and Child Neurology, 27, 675-685.
- Roberts, K. (1997). A preliminary account
of the effect of otitis media on 15-month-olds' categorization and some
implications for early language learning. Journal of Speech, Language
and Hearing Research, 40, 508-518.
M. L., Bauer, H. R., & Tyler, A. A. (1994). A quantitative analysis
of the single word stage. First Language, 14, 37-48.
- Robbins, J., & Klee, T.
(1987). Clinical assessment of oropharyngeal motor development in young
children. Journal of Speech and Hearing Disorders, 52, 271-277.
- Rosenberg, S., &
Abbeduto, L. (1993). Language and Communication in Mental Retardation:
Development, Process, and Intervention. Hillsdale, NJ: Lawrence Erlbaum
Rosin, M. M., Swift, E., Bless, D. & Vetter, D. K. (1988). Communication
profiles of adolescents with Down syndrome. Journal of Childhood Communication
Disorders, 12(1), 49-64.
- Shriberg, L., & Widder,
C. J. (1990). Speech and prosody characteristics of adults with mental
retardation. Journal of Speech and Hearing Research, 33, 627-653.
- Smith, B. L. (1977). Phonological
development in Down's syndrome children. Paper presented at the 85th
Annual Convention of the American Psychological Association, San Francisco,
- Smith, B. L. (1984). Implications
of infant vocalizations for assessing phonological disorders. In N. J. Lass
(Ed.), Speech and Language: Advances in Basic Research: Vol. 11
(pp. 169-194). New York: Academic Press.
- Smith, B. L., & Oller,
D. K. (1981). A comparative study of pre-meaningful vocalizations produced
by normally developing and Down's syndrome infants. Journal of Speech
and Hearing Disorders, 46, 46-51.
- Smith, B. L.,
& Stoel-Gammon, C. (1983). A longitudinal study of the development of
stop consonant production in normal and Down's syndrome children. Journal
of Speech and Hearing Disorders, 48, 114-118.
- Smith, B. L.,
& Stoel-Gammon, C. (1996). A quantitative analysis of the reduplicated
and variegated babbling in vocalizations by Down syndrome infants. Clinical
Linguistics and Phonetics, 10, 119-130.
- Smith, L., & von
Tetzchner, S. (1986). Communicative, sensorimotor and language skill
of young children with Down syndrome. American Journal of Mental Deficiency,
- Smith, L., von Tetzchner, S., & Michalson, B. (1988). The emergence
of language skill in young children with Down syndrome. In L. Nadel (Ed.),
The Psychobiology of Down Syndrome (pp. 145-165). Cambridge, MA:
R. K., Patterson, J. P. & Wildgen, P. L. (1988). Phonology of Down syndrome
speakers, ages 13-22. Journal of Childhood Communication Disorders,
Sommers, R. K., Reinhart, R. W., & Sistrunk, D. A. (1988). Traditional
articulation measures of Down syndrome speakers, ages 13-22. Journal
of Childhood Communication Disorders, 12(1), 93-108.
Steffens, M. L., Oller, D. K., Lynch, M., & Urbano, R.C. (1992). Vocal
development in infants with Down syndrome and infants who are developing
normally. American Journal of Mental Retardation, 97, 235-246.
- Stoel-Gammon, C. (1980). Phonological
analysis of four Down's syndrome children. Applied Psycholinguistics,
- Stoel-Gammon, C. (1981). Speech
development of infants and children with Down's syndrome. In J. K. Darby
(Ed.), Speech Evaluation in Medicine (pp. 341-360). New York: Grune
and Stratton, Inc.
- Stoel-Gammon, C. (1985). Phonetic
inventories, 15-24 months: A longitudinal study. Journal of Speech and
Hearing Research, 28, 505-512.
- Stoel-Gammon, C. (1992). Prelinguistic
vocal development: Measurement and predictions. In C. A. Ferguson, L. Menn,
& C. Stoel-Gammon (Eds.), Phonological Development: Models, Research,
Implications (pp. 439-456). Timonium, MD: York Press.
- Stoel-Gammon, C. (1998). The role
of babbling and phonology in early linguistic development. In A. M. Wetherby,
S. F. Warren, & J. Reichle (Eds.), Transitions in Prelinguistic Communication:
Preintentional to Intentional and Presymbolic to Symbolic (pp. 87-110).
Baltimore: Paul H. Brookes.
- Stray-Gunderson, K. (1986).
Babies with Down Syndrome: A New Parents Guide. Rockville, MD:
- Swift, E. & Rosin, P. (1990).
A remediation sequence to improve speech intelligibility for students with
Down syndrome. Language, Speech, and Hearing Services in Schools,
- Van Borsel, J. (1996). Articulation
in Down's syndrome adolescents and adults. European Journal of Disorders
of Communication, 31, 415-444.
S., Mangipudi, L., & Locke, J. (1989) Prelinguistic phonetic contingency:
Data from Down syndrome. First Language, 9, 159-174.
Wallace, I. F., Gravel, J. S., McCarton, C. M., & Ruben, R. J. (1988).
Otitis media and language development at 1 year of age. Journal of Speech
and Hearing Disorders, 53, 245-251.
- Warren, S.F. & Yoder,
P.J. (1997). Emerging model of communication and language intervention.
Mental retardation and Developmental Disabilities Research Reviews,
- Weinberg, B., & Zlatin,
M. (1970). Speaking fundamental frequency characteristics of five- and
six-year-old children with mongolism. Journal of Speech and Hearing
Research, 13, 418-425.
- Yarter, B. H. (1980). Speech and
language programs for the Down's population. Seminars in Speech, Language
and Hearing, 1, 49-61.
See and Learn Speech is designed to help parents and educators support children with Down syndrome to develop clearer speech.
See and Learn Speech offers a structured approach to support speech development, working in small steps towards clearer speech production.
Now available as teaching kits and apps.
Find out more...