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·                  

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JSLHR

Article

Effects of Sampling Context on Spontaneous
Expressive Language in Males With Fragile

X Syndrome or Down Syndrome
Sara T. Kover,a Andrea McDuffie,b Leonard Abbeduto,b and W. Ted Brownc

Purpose: In this study, the authors examined the impact of
sampling context on multiple aspects of expressive language in
male participants with fragile X syndrome in comparison to male
participants with Down syndrome or typical development.
Method: Participants with fragile X syndrome (n = 27), ages
10–17 years, were matched groupwise on nonverbal mental
age to adolescents with Down syndrome (n = 15) and typically
developing 3- to 6-year-olds (n = 15). Language sampling
contexts were an interview-style conversation and narration
of a wordless book, with scripted examiner behavior. Language
was assessed in terms of amount of talk, mean length of
communication unit (MLCU), lexical diversity, fluency, and
intelligibility.
Results: Participants with fragile X syndrome had lower MLCU and
lexical diversity than did participants with typical development.

Participants with Down syndrome produced yet lower MLCU.
A differential effect of context among those with fragile X syndrome,
Down syndrome, and typical development emerged for the
number of attempts per minute, MLCU, and fluency. For participants
with fragile X syndrome, autism symptom severity related to the
number of utterances produced in conversation. Aspects of
examiner behavior related to participant performance.
Conclusion: Sampling context characteristics should be
considered when assessing expressive language in individuals
with neurodevelopmental disabilities.

Key Words: language sampling, conversation, narrative, fragile
X syndrome, mean length of utterance (MLU)

O f the methods used to assess expressive languagein children and adolescents with intellectual dis-abilities, standardized tests and spontaneous
language samples are the most often used (Abbeduto,
Kover, & McDuffie, 2012). Although scores on standard-
ized assessments and language samples tend to be corre-
lated, each provides unique information (Condouris,
Meyer, & Tager-Flusberg, 2003; Ukrainetz & Blomquist,
2002). Standardized measures of expressive language
offer a relatively quick evaluation of performance relative

to age expectations. However, most standardized assess-
ments yield a single summary score for expressive
language ability, which precludes the possibility of identi-
fying patterns of relative strength or weakness across
domains (e.g., vocabulary, syntax), and can mask clinically
meaningful differences among individuals. When assess-
ing individuals with intellectual disabilities, standard-
ized language tasks are also prone to floor effects (Mervis
& Robinson, 2005). Spontaneous language samples avoid
these limitations by providing contextualized data on spe-
cific aspects of ability and, in this way, are well suited to
establishing expressive language profiles (Westerveld,
Gillon, & Miller, 2004). The present study was designed
to further explore the utility of language-sampling proce-
dures for individuals with intellectual disabilities.

In using language samples to characterize any
population with disabilities, it is important to recognize
that the nature of the language-sampling context can af-
fect the language produced by the child and, consequently,
the conclusions reached by the researcher or clinician.
In this study, we focused on the ways in which sam-
pling context impacts the characterization of expressive

aWaisman Center, University of Wisconsin—Madison
bM.I.N.D. Institute, University of California, Davis
cNew York State Institute for Basic Research in Developmental
Disabilities, Staten Island

Correspondence to Sara T. Kover: kover@wisc.edu

Editor: Janna Oetting
Associate Editor: Elizabeth Crais

Received March 28, 2011
Revision received September 6, 2011
Accepted November 22, 2011
DOI: 10.1044/1092-4388(2011/11-0075)

Journal of Speech, Language, and Hearing Research • Vol. 55 • 1022–1038 • August 2012 • D American Speech-Language-Hearing Association1022

language in individuals with specific neurodevelopmen-
tal disabilities associated with intellectual disability.
In particular, we assessed language in two contexts,
conversation and narration, in male adolescents with
fragile X syndrome, male adolescents with Down syn-
drome, and boys with typical development at similar
levels of nonverbal cognitive development.

Contexts for Sampling
Spontaneous Language

Research on children with typical development or
language impairment suggests that sampling contexts
vary in the extent to which they elicit the upper bound
of an individual’s linguistic ability (Southwood & Russell,
2004; Thordardottir, 2008; Wagner, Nettelbladt, Sahlen,
& Nilholm, 2000). Interview-style conversations, for
instance, elicit more utterances and utterances with
higher mean length of utterance (MLU) relative to
free-play contexts (Evans & Craig, 1992; Southwood &
Russell, 2004); however, narrative contexts may be opti-
mal for assessing syntactic ability because they elicit
longer and more complex sentences than either conver-
sation or free play, on average (MacLachlan & Chapman,
1988; Westerveld et al., 2004). In terms of disabilities,
high-functioning children with autism have been
shown to demonstrate a weakness in complex syntax rel-
ative to typically developing children during personal
narratives but not when telling a story from a wordless
book, demonstrating differences between contexts, even
for children in the normal range of cognitive functioning
(Losh & Capps, 2003).

Context effects also have been described for individ-
uals with intellectual disabilities. Abbeduto, Benson,
Short, and Dolish (1995), for example, examined the
language of children and adolescents with intellec-
tual disability of unspecified etiology and found more
communication attempts per minute in a conversation
than in narration, whereas language produced in narra-
tion had a higher mean length of communication unit
(MLCU) than in conversation. Abbeduto et al. suggested
that narration more fully engages the syntactic abilities
of individuals with intellectual disability because narra-
tive revolves around content more likely to be encoded in
multiclause utterances (e.g., cause and effect, psycholog-
ical states). Likewise, the visual scaffolding provided by
a wordless storybook in a narrative context can free up
cognitive resources, such as working memory, which
might also support the production of more complex sen-
tences (Miles, Chapman, & Sindberg, 2006). Thus, vari-
ation in the characteristics of the sampling context can
affect conclusions reached about an individual with in-
tellectual disability. From a clinical perspective, such
findings suggest the need for multiple sampling contexts
and to understand the advantages and disadvantages of

each. In this study, we were interested in the possible
differential effects of context on the language of individ-
uals with intellectual disabilities.

Consistency Within Language-
Sampling Contexts

Difficulties with the interpretation of individual
or diagnostic group differences in expressive language
profiles can arise from inadequate consistency of proce-
dures within a given context. In particular, performance
can be affected by variations in materials, partners, and
experimenter behavior (Dollaghan, Campbell, & Tomlin,
1990; Hansson, Nettelbladt, & Nilholm, 2000). In con-
versation, for example, the amount of talk and rate of
questioning by a partner can influence both the child’s
amount of talk and MLU (Cowan, Weber, Hoddinott,
& Klein, 1967; Evans & Craig, 1992; Johnston, 2001;
Johnston, Miller, Curtiss, & Tallal, 1993). Thus, failure
to consistently structure the sampling context and script
examiner behavior across participants could result in
uninterpretable differences across individuals, diag-
nostic groups, and studies because differences in lan-
guage ability cannot be distinguished from variations
attributable to the sampling context. In the present
study, we created procedures and scripts for consis-
tently structuring critical aspects of our two language-
sampling contexts, thereby allowing unambiguous
interpretation of differences in performance across diag-
nostic groups.

Although it is important to structure and script the
language-sampling context, this “standardization” must
be flexible enough to allow the examiner to adapt his or
her behavior to the skill level and interaction style of the
child. Consequently, even within the constraints of a
structured procedure, variation in the amount and com-
plexity of examiner talk can emerge as the examiner
attempts to engage the individual in the language sam-
pling task. For example, an examiner’s syntactic complex-
ity, as reflected in complex sentence use, has been found
to be positively correlated with child MLU, lexical diver-
sity, and morphosyntactic complexity in school-age chil-
dren with language impairments (Dethorne & Channell,
2007). This correlation was found despite the fact that
for each child, the language sample was 15 min long,
elicited with a standard set of toys, and followed Leadholm
and Miller’s (1992) recommendations for language sam-
pling (e.g., use of open-ended questions). Although it is
difficult to determine causality in such a pattern of con-
current relationships, it is important to document them.
In the present study, we used structured procedures
that were highly prescriptive with respect to examiner
behavior, but allowed for responsiveness and adapta-
tion to the participant. We then evaluated the relation-
ship between examiners’ language and the language

Kover et al.: Context Effects 1023

produced by participants with fragile X syndrome, who
were the focus of this study, and those with Down syn-
drome or typical development, as points of comparison.

Fragile X Syndrome
Fragile X syndrome is the leading cause of inherited

intellectual disability. It is caused by a cytosine-guanine-
guanine (CGG) trinucleotide expansion beyond 200 re-
peats on the FMR1 gene of the X chromosome (Verkerk
et al., 1991). In addition to intellectual disabilities, ap-
proximately one third of males with fragile X syndrome
meet diagnostic criteria for autism, with many of the re-
mainder displaying symptoms of autism, including ste-
reotyped language (Bailey et al., 1998; Hagerman, 2008;
Hagerman, Jackson, Levitas, Rimland, & Braden, 1986;
Rogers, Wehner, & Hagerman, 2001).

Delays in vocabulary and syntax are present in both
receptive and expressive language for the majority of
males with fragile X syndrome regardless of the extent
of autism symptoms (Abbeduto, Brady, & Kover, 2007).
Expressive language is usually delayed relative to chro-
nological age in males with fragile X syndrome, although
it may be commensurate with nonverbal cognition when
assessed with standardized measures (Finestack &
Abbeduto, 2010; Roberts, Price, et al., 2007). Relatively
few studies, however, have thoroughly described the
spontaneous expressive language abilities of individuals
with fragile X syndrome.

Spontaneous expressive language in fragile X syn-
drome. Spontaneous expressive language in males
with fragile X syndrome generally has been character-
ized as rapid, repetitive, disfluent, and unintelligible
(Belser & Sudhalter, 2001; Ferrier, Bashir, Meryash,
Johnston, & Wolff, 1991; Hanson, Jackson, & Hagerman,
1986; Paul, Cohen, Breg, Watson, & Herman 1984;
Van Borsel, Dor, & Rondal, 2008); however, early studies
have produced some conflicting results. For example,
some studies of males with fragile X syndrome pointed
to a specific delay in MLU relative to nonverbal mental
age (e.g., Paul et al., 1984), whereas others failed to find
weaknesses in MLU compared with cognitive-level
expectations (e.g., Ferrier et al., 1991).

In a recent series of studies, Roberts and colleagues
(Roberts, Hennon, et al., 2007; Roberts, Martin, et al.,
2007; Price et al., 2008; Barnes et al., 2009) analyzed lan-
guage samples collected during the Autism Diagnostic
Observation Schedule (ADOS; Lord, Rutter, DiLavore,
& Risi, 1999). Participants included boys between the
ages of 3 and 16 years who were categorized as having
either only fragile X syndrome or comorbid fragile X syn-
drome and autism spectrum disorder (ASD), as deter-
mined by the ADOS. In one study, boys with only fragile
X syndrome were found to perform more poorly on lexical

diversity, MLU, and the Index of Productive Syntax
(IPSyn; Scarborough, 1990) relative to typically develop-
ing boys after controlling for nonverbal mental age, in-
telligibility, and maternal education (Roberts, Hennon,
et al., 2007). In a follow-up study, Price et al. (2008)
found that boys with fragile X syndrome with and with-
out comorbid ASD and boys with Down syndrome had
lower MLU and IPSyn scores than typically developing
boys after controlling for nonverbal mental age and ma-
ternal education.

Additional analyses by Roberts and colleagues
focused on other aspects of spoken language using
these same language samples. Boys with fragile X syn-
drome, with and without comorbid ASD, produced fewer
intelligible words in connected speech than typically de-
veloping boys and did not differ from those with Down
syndrome in this regard, controlling for nonverbal men-
tal age (Barnes et al., 2009). In terms of pragmatics, boys
with comorbid fragile X syndrome and ASD displayed
more noncontingent talk than boys with fragile X syn-
drome only, Down syndrome, or typical development in
utterances that were collected equally from free-play
versus other ADOS activities. In addition, boys with
fragile X syndrome produced more perseverative lan-
guage than boys with Down syndrome or typical devel-
opment regardless of ASD status (Roberts, Martin,
et al., 2007).

Limitations of previous research. Although previous
studies in which spontaneous expressive language in
fragile X syndrome has been examined are informative,
most have been based on small samples, poorly struc-
tured sampling contexts, or language samples collected
in a single context. The studies of Roberts and colleagues,
for example, included a wide age range of males and in-
corporated a protocol that was not designed specifically
for the elicitation of language samples. Although the
ADOS provides a standard set of activities, the nature
of the activities, the amount of time spenton each activity,
and the level of examiner prompting might vary within
and across modules as well as across participants. For
example, conversation and telling a story from a book
are probed in Modules 2 and 3, but not Module 1; free
play appears in Modules 1 and 2, but not Module 3.
Due to potentially important variations in materials
and examiner behavior, the ADOS may not provide the
ideal sampling context from which to draw conclusions
about language profiles within and across groups of in-
dividuals with neurodevelopmental disabilities, although
it is considered the gold standard for assessing autism
symptoms.

In addition, most research has addressed the potential
impact of autism symptoms on language performance in
individuals with fragile X syndrome from a categorical
perspective by either (a) comparing participants with

1024 Journal of Speech, Language, and Hearing Research • Vol. 55 • 1022–1038 • August 2012

or without a comorbid autism or ASD diagnosis (e.g., Price
et al., 2008) or (b) excluding participants with comorbid
autism from analyses (e.g., Roberts, Hennon, et al.,
2007). Despite the contributions of this research, there
is a need to move beyond dichotomizing the fragile
X syndrome phenotype according to cut offs for diagnos-
ing individuals with idiopathic autism. Such cut offs,
although displaying adequate levels of sensitivity and
specificity for individuals with idiopathic autism,
might not be suited to characterizing variation among
individuals with neurodevelopmental disabilities other
than autism, particularly given that autism symptoms
are present to some degree in most males with fragile
X syndrome (Hall, Lightbody, Hirt, Rezvani, & Reiss,
2010; Moss & Howlin, 2009). Instead, including partici-
pants with all levels of autism symptom severity and
considering the incremental impact of increased autism
symptomology on language performance is likely to be
more informative with respect to the full range of the
phenotype in fragile X syndrome (McDuffie, Kover,
Abbeduto, Lewis, & Brown, 2012; Moss & Howlin,
2009). Thus, we included all participants with fragile
X syndrome in group comparisons regardless of their
potential autism-diagnostic status and examined vari-
ability within fragile X syndrome by evaluating the
relationship between language performance and a con-
tinuous scale of autism symptom severity derived from
the ADOS.

Down Syndrome
Down syndrome is the leading genetic cause of intel-

lectual disability and, in most cases, results from a third
copy of chromosome 21 (Chapman & Hesketh, 2000).
Autism can occur in individuals with Down syndrome,
but it is less common than in fragile X syndrome, with
prevalence estimates of approximately 10% (Hepburn,
Philofsky, Fidler, & Rogers, 2008; Kent, Evans, Paul,
& Sharp, 1999). Language is significantly impaired
in Down syndrome compared with nonverbal cognition,
with expressive language more delayed than recep-
tive language, and syntax delayed beyond vocabulary
(Chapman & Hesketh, 2001). Individuals with Down
syndrome provide a useful comparison to those with
fragile X syndrome because their distinct impair-
ments may differentially affect their ability to meet
the demands of any given language-sampling task,
thereby yielding information about etiological differ-
ences in the effects of sampling context on expressive
language.

Spontaneous expressive language in Down syn-
drome. Research on expressive language in Down syn-
drome has yielded more consistent results than studies
on fragile X syndrome, particularly in terms of a relative
delay in syntactic complexity (Laws & Bishop, 2003).

Roberts and colleagues, as described above, found that
males with Down syndrome had lower MLU and
IPSyn scores when controlling for nonverbal cognition
and maternal education than males with fragile X syn-
drome or typical development (Price et al., 2008).

Even for individuals with Down syndrome, however,
language-sampling contexts can have differential effects
on expressive language. Miles and colleagues (2006)
assessed interview-style conversation and narrative
performance in 14 adolescents with Down syndrome,
12–21 years of age, relative to 14 typically developing
children who were matched on receptive language abil-
ity. Although the MLU of the typically developing
children did not differ across the conversation and
narration contexts, the narrative context yielded sig-
nificantly higher MLU for participants with Down
syndrome. In fact, MLU did not differ between par-
ticipants with Down syndrome and typically devel-
oping children in the narrative context. This work
illustrates the nuanced characterization of expressive
language ability that can emerge from the comparison
of language elicited in multiple, carefully structured
language-sampling contexts. Whether similar effects of
sampling context extend to other neurodevelopmental
disabilities, such as fragile X syndrome, remains to be
determined.

Comparisons Between Fragile X Syndrome
and Down Syndrome

Little research has compared the expressive lan-
guage profiles of adolescents with fragile X syndrome
and Down syndrome using structured sampling contexts
designed to elicit spontaneous language, with the excep-
tion of a series of studies by Abbeduto and colleagues.
Two studies examined performance only in a narrative
context and demonstrated that adolescent and young
adult males and females with fragile X syndrome used
more grammatically correct and complex utterances
than did participants with Down syndrome (Finestack
& Abbeduto, 2010; Keller-Bell & Abbeduto, 2007).
Examining both a conversation and a narrative context,
Kover and Abbeduto (2010) reported several effects
of context (e.g., greater MLCU and fluency, but poorer
lexical diversity, in narration than in conversation) for
older adolescents with fragile X syndrome or with
Down syndrome, but lacked a comparison group of typi-
cally developing participants, making the expressive
language profiles more difficult to interpret. We extend
the findings of these studies in the present study by eval-
uating the effect of context (i.e., conversation vs. narra-
tion) on multiple aspects of expressive language ability,
including the extent to which younger male adolescents
with fragile X syndrome or Down syndrome successfully
completed the language-sampling tasks.

Kover et al.: Context Effects 1025

Research Aims
The present study was designed to examine the

effects of language-sampling context on the expressive
language profiles of males with fragile X syndrome
using structured conversation and narration sampling
contexts. The performance of males with fragile X syn-
drome was compared with that of adolescents with
Down syndrome and typically developing boys at similar
levels of nonverbal cognitive development to assess the
possibility that sampling context differentially affects
individuals with different neurodevelopmental disabil-
ities. For participants with fragile X syndrome, we also
explored the impact of autism symptom severity on per-
formance. Finally, the relationship of examiner behavior
to the language produced was examined to probe the
potential benefits and limitations of these sampling
contexts.

Method
Participants

Participants (N = 57) were boys drawn from a large
longitudinal project on language development. Youth
with fragile X syndrome were recruited nationally (see
McDuffie et al., 2010); those with Down syndrome or typ-
ical development were recruited primarily locally. Parti-
cipants with typical development were not receiving
special education services and had no significant sensory
or motor impairments according to parent report.
All participants were native English speakers and
were reported by a parent to regularly use three-word
phrases. Approximately 95% of the participants were
Caucasian. Approximately 85% of typically developing
boys had mothers with a college degree or higher com-
pared with approximately 50% of participants with frag-
ile X syndrome or Down syndrome. Although several
sibling pairs participated, only one child per family
was included in the analyses reported here. This sample
overlaps with that of McDuffie et al. (2010) and Pierpont
et al. (2011), although the primary measures differ. The
project was Institutional Review Board approved.

Each participant contributed one conversation sam-
ple and one narration sample from a single time point.
Exclusions of participants from the present analyses
were made on the basis of incomplete conversations or
narrations or level of nonverbal cognitive ability. Three
participants with Down syndrome from the larger proj-
ect were not included in the present sample because they
did not complete one or both language-sampling tasks at
any visit. One participant with fragile X syndrome from
the larger project was not included in the sample be-
cause his conversation was only 5 min in duration. Par-
ticipants were included in the present analyses only if

they completed the narrative task in a meaningful
way—that is, the child produced an utterance relevant
to the storybook for at least 12 of the 16 pages. Three par-
ticipants with fragile X syndrome and two participants
with Down syndrome were not included in the present
analyses because they failed to meet this criterion. The
analyzed language samples were collected during the
first annual assessment for all but five participants
with fragile X syndrome and three participants with
Down syndrome, who failed to engage in the language-
sampling tasks at previous annual visits. Because these
participants had not successfully engaged in the tasks
during prior visits, data for all participants reflect
their first completion of the language-sampling activi-
ties. Finally, four participants with typical development
and six participants with fragile X syndrome were ex-
cluded because their nonverbal mental ages were higher
than would allow valid comparisons across all three
groups, as described below. The foregoing exclusions
resulted in the following samples for the present analy-
ses: 10- to 17-year-olds with fragile X syndrome (n = 27)
or Down syndrome (n = 15) and 3- to 6-year-old boys with
typical development (n = 15).

Participants with fragile X syndrome or Down syn-
drome had a confirmed genetic diagnosis. Of those with
fragile X syndrome, all had molecular genetic test
results indicating the full mutation or mosaicism (i.e.,
full and premutation cells; n = 7). Karyotypes confirming
trisomy 21 were available to the project for 13 of the
15 participants with Down syndrome; however, for the
remaining two participants, Down syndrome was listed
as the diagnosis in educational or medical reports and
corroborated by parent report.

We administered the Leiter-R Brief IQ Screener
(Roid & Miller, 1997), which yields both a standard
score (nonverbal IQ) and an age-equivalent score (non-
verbal mental age). Nonverbal mental age was obtained
by averaging the subtest age equivalents associated
with the earned raw scores over all completed subtests.
To ensure that group comparisons were not confounded
by differences in nonverbal mental age, participants
were selected such that there were no significant
group differences in nonverbal mental age. To achieve
this groupwise matching while also maximizing sample
sizes, comparisons of the participants with fragile X syn-
drome to those with Down syndrome or typical develop-
ment were limited to participants whose nonverbal
mental age scores ranged between 3.1 and 6.54, yielding
the 57 participants included in the analyses described
here. Participant characteristics are shown in Table 1.
Participants with fragile X syndrome had Leiter Brief
IQs between 36 and 62; participants with Down syn-
drome had Leiter Brief IQs between 36 and 54, and typ-
ically developing boys had Leiter Brief IQs between 87
and 127.

1026 Journal of Speech, Language, and Hearing Research • Vol. 55 • 1022–1038 • August 2012

All but one participant with fragile X syndrome
received the ADOS (n = 26), usually at the first annual
assessment. Examiners were trained to research reli-
ability. Because variability in the Down syndrome phe-
notype due to autism symptomology was not the focus of
the present study, individuals with Down syndrome
were not screened for autism. Autism severity scores,
ranging from 1 (nonspectrum) to 10 (autism, highest
possible severity score), were assigned to participants
with fragile X syndrome according to the chronological
age, module administered, and total algorithm score
from the ADOS (Gotham, Pickles, & Lord, 2009). Of the
26 participants with fragile X syndrome who received
the ADOS, 10 fell in the nonspectrum range (i.e., severity
scores ranging from 1 to 3), one fell in the ASD range (i.e.,
severity scores of 4 or 5), and 15 fell in the autism range
(i.e., severity scores ranging from 6 to 10). The mean se-
verity score was 5.81, with a standard deviation of 3.19.

Measurement of Expressive
Language Abilities

Expressive language abilities were assessed by
eliciting spontaneous speech in two distinct sampling
contexts, as described by Abbeduto et al. (1995): an
interview-style conversation and a narration of a word-
less picture book.

In the conversation, each participant talked with
one of several female examiners for a target time of
10 min, during which the examiner’s goal was to keep
her talk to a minimum. The examiner said that she
would like to get to know the participant better and
asked open-ended questions, while avoiding yes/no ques-
tions as much as possible. Consistency across partic-
ipants was ensured with a scripted order of topics and
follow-up questions; however, the amount of time spent
on a topic was based on the participant’s interests. The
topics included school, teachers, pets, and so forth, and
were introduced in a broad manner, such as “Do you
have any pets? Tell me about them.” Follow-up probes
were also broad (e.g., “Tell me what you like about your
pet”). All but two conversations elicited from participants

with fragile X syndrome and two from participants with
typical development reached the 10-min target. Because
of logistical constraints or participant engagement,
these four conversations were nearly 8 min.

In the narration activity, participants were shown
one of two wordless picture books, Frog Goes to Dinner
(Mayer, 1974) or Frog on His Own (Mayer, 1973), alter-
nating between participants in the larger study. No sig-
nificant differences in performance between books was
found for any of the seven dependent variables of inter-
est described below (all ps > .18). In this sample of
57 participants, Frog Goes to Dinner was told by 59%
of participants with fragile X syndrome, 53% of partici-
pants with Down syndrome, and 47% of participants
with typical development. The participant was told
that he would look at the book and then be asked to
tell the story. The examiner turned the pages of the
book one by one, allowing the participant to look at
each for about 10 s on the initial viewing. The partici-
pant then was asked to tell everything about the story
for each page. This time through, the experimenter
turned to the next page 5 s after the participant had fin-
ished narrating a page. The examiner was restricted to
scripted prompts if the participant did not respond to the
first page (e.g., “What about the boy? What’s he doing,
thinking, and feeling?”). If the participant did not talk
on subsequent pages, the examiner’s scripted prompts
were more limited (e.g., “What’s happening in this part
of the story?”). Narratives ranged from 1 to 7 min for the
participants with fragile X syndrome, from 3 to 8 min for
participants with typical development, and from 3 to
11 min for participants with Down syndrome.

The language samples were recorded onto audio
tapes and transcribed using Systematic Analysis of Lan-
guage Transcripts software (Miller & Iglesias, 2006)
according to research conventions. An experienced pri-
mary transcriber first transcribed each sample. A
second trained transcriber then listened to the tape
and marked suggested changes or perceived discrepan-
cies on every transcript. The primary transcriber then
verified or updated the transcript for each language
sample before the data were analyzed. The first 10 min

Table 1. Participant characteristics.

Participant group n

Chronological age Nonverbal IQa Nonverbal age equivalent

M (SD) M (SD) M (SD)

Fragile X syndrome 27 12.70 (1.84) 44.15 (6.72) 5.08 (0.73)
Down syndrome 15 12.99 (2.02) 41.33 (6.03) 4.73 (0.75)
Typical development 15 4.67 (1.12) 107.80 (12.25) 4.95 (1.03)

Note. The sample of boys with fragile X syndrome (n = 27) includes participants regardless of autism symptom severity.
aDue to a missing subtest, one participant with fragile X syndrome lacked a nonverbal IQ score.

Kover et al.: Context Effects 1027

of each conversation were transcribed, whereas each
narrative was transcribed in its entirety. For 17 partici-
pants from the larger project, conversation and/or nar-
ration samples were independently transcribed again
in the manner described to assess interrater agreement.
Intertranscriber agreement including utterance seg-
mentation and morpheme-level variables averaged
90% across contexts and groups (see Table 2).

Expressive language variables. All speech was seg-
mented into communication units (C-units). A C-unit is
defined as an independent clause and any of its modi-
fiers, including dependent clauses (Loban, 1976). Seg-
menting speech into C-units, as opposed to utterances,
avoids overestimating language abilities for long but
simple utterances combined with coordinating conjunc-
tions (Abbeduto et al., 1995; Scarborough, Rescorla,
Tager-Flusberg, Fowler, & Sudhalter, 1991). The C-unit
is the unit of analysis in the present study.

The amount of talk was assessed in terms of (a) the
total number of C-units produced, (b) the number of
complete and intelligible C-units produced, and (c) the
number of C-units attempted per minute (including
incomplete C-units). Language ability was assessed in
terms of MLCU, lexical diversity, fluency, and intelligi-
bility. MLCU was defined as the mean number of mor-
phemes per complete and intelligible C-unit. Lexical
diversity was defined as the total number of lexical
word roots in the language sample, reflecting range of
vocabulary use. Fluency was calculated as the propor-
tion of C-units containing mazes, such as filled pauses
and partial or full repetitions. Intelligibility was defined
as the proportion of C-units partially or fully unintelligi-
ble during transcription.

Results

Comparison of Fragile X Syndrome, Down
Syndrome, and Typical Development

We assessed profiles of expressive language abilities
in a comparison of all participants with fragile X syndrome

(n = 27), Down syndrome (n = 15), and typical develop-
ment (n = 15). Participants with fragile X syndrome
and those with Down syndrome did not differ in terms
of chronological age, t(40) = 0.53, p = .600, or nonverbal
IQ, t(40) = 1.04, p = .305. The three groups did not differ
in nonverbal mental age, F(2, 54) = 0.91, p = .410; how-
ever, because the p ≥ .50 matching criteria suggested by
Mervis and Robinson (1999) was not reached, nonverbal
mental age was included as a covariate in these analy-
ses. As such, we conducted repeated measures analyses
of covariance to test the effects of context, group, and
their interaction. We conducted planned comparisons
following omnibus tests with Shaffer’s (1986) postomni-
bus procedure.

Amount of talk. The unadjusted scores for the
amount of language produced are presented in Table 3.
The total number of C-units produced was higher in
conversation than in narration, F(1, 53) = 5.44, p = .024,
hp

2 = .09. There was neither an effect of group, F(2,
53) = 2.09, p = .133, nor an interaction between context
and group, F(2, 53) = 1.82, p = .173, for the number of
C-units produced. The number of complete and intelligi-
ble utterances was higher in conversation than in narra-
tion, but just failed to reach significance, F(1, 53) = 3.88,
p = .054. There was also no effect of group, F(2, 53) =
0.58, p = .562, or Context × Group interaction, F(2, 53) =
0.50, p = .612, for complete and intelligible utterances.

For the number of C-units attempted per minute,
the interaction between context and group was signifi-
cant, F(2, 53) = 5.99, p = .005, hp

2 = .18. The differential
effect of context across groups was significant for fragile
X syndrome versus Down syndrome, t(53) = 3.41,
p = .001, and Down syndrome versus typical develop-
ment, t(53) = 2.43, p = .018, but not fragile X syndrome
versus typical development, t(53) = 0.69, p = .492. Partici-
pants with Down syndrome showed the largest effect of
context with few C-units attempted during narration
compared with conversation relative to participants
with typical development and participants with fragile
X syndrome. Neither the main effect of context, F(1,
53) = 3.37, p = .072, nor the main effect of group was sig-
nificant, F(2, 53) = 2.83, p = .068.

Language ability. Results for expressive language
ability are presented in Table 4. For MLCU, the main ef-
fect of context was not significant, F(1, 53) = 1.26,
p = .267, but there was an effect of group with the partic-
ipants with typical development outperforming those
with fragile X syndrome, who in turn scored higher
than those with Down syndrome, F(2, 53) = 17.55,
p < .001, hp

2 = .40, one-tailed ps < .05. There was also an interaction between context and group for MLCU, F(2, 53) = 4.20, p = .020, hp

2 = .14. The differential effect
of context across groups was significant for fragile X syn-
drome versus typical development, t(53) = 2.87, p = .006,
and just failed to reach significance for Down syndrome

Table 2. Transcription reliability.

Participant group

Conversation Narration

n % agreement n % agreement

Fragile X syndrome 6 91 6 90
Down syndrome 5 87 5 86
Typical development 5 92 5 94

Note. Percentage (%) agreement is averaged over utterance segmentation,
intelligibility, mazes, overlaps, pauses, abandonment, word identification,
number of morphemes and words, and ending punctuation.

1028 Journal of Speech, Language, and Hearing Research • Vol. 55 • 1022–1038 • August 2012

versus typical development, t(53) = 1.91, p = .061. The
effect of context on MLCU did not differ between partic-
ipants with fragile X syndrome and Down syndrome,
t(53) = 0.69, p = .496. Boys with typical development
showed little effect of context on MLCU compared
with the other groups, with those with fragile X
syndrome producing higher MLCU in narration than
in conversation.

For lexical diversity, range of vocabulary use dif-
fered among groups, F(2, 53) = 4.32, p = .018, hp

2 = .14,
with better performance by the typically developing boys
than participants with fragile X syndrome or Down syn-
drome (ps < .05), who did not differ (p = .211). There was no effect of context, F(1, 53) = 0.10, p = .757, or interac- tion, F(2, 53) = 2.54, p = .089.

Fluency differed among groups, F(2, 53) = 3.90,
p = .026, hp

2 = .13, and was a strength of the participants
with fragile X syndrome relative to those with Down syn-
drome (p = .008). There was also an interaction between

group and context, F(2, 53) = 7.03, p = .002, hp
2 = .21. The

effect of context differed across all groups: fragile X syn-
drome versus Down syndrome, t(53) = 2.04, p = .046;
fragile X syndrome versus typical development, t(53) =
2.19, p = .033; and Down syndrome versus typical devel-
opment, t(53) = 3.75, p < .001. Participants with fragile X syndrome showed similar fluency in both contexts; par- ticipants with Down syndrome were more fluent (i.e., produced a smaller proportion of C-units with mazes) during conversation than narration, whereas partici- pants with typical development were more fluent during narration. The main effect of context was not significant, F(1, 53) = 0.41, p = .526.

Intelligibility differed among groups, F(2, 53) = 9.10,
p < .001, hp

2 = .26, such that it was a weakness of parti-
cipants with Down syndrome relative to those with frag-
ile X syndrome and those with typical development
(ps < .002). Participants with fragile X syndrome were less intelligible than those with typical development,

Table 4. Language performance in conversation and narration.

Participant group n

MLCU Lexical diversitya Fluencyb Intelligibilityc

M SD Range

M SD Range M SD Range M SD Range

Conversation
Fragile X syndrome 27 3.75 1.45 1.32–7.05 143.85 70.45 38–313 18 13 0–42 12 8 2–37
Down syndrome 15 3.06 0.80 1.84–4.32 115.00 30.69 59–171 23 17 1–66 20 12 9–57
Typical development 15 5.52 1.26 3.30–7.05 173.73 50.80 72–236 27 10 11–48 6 4 1–13

Narration
Fragile X syndrome 27 4.85 1.36 2.17–7.37 62.26 22.34 28–127 17 10 2–34 10 8 0–28
Down syndrome 15 3.94 1.23 1.40–6.00 50.27 21.63 14–79 31 19 4–68 20 18 3–67
Typical development 15 5.59 0.93 4.07–7.11 67.20 18.35 38–100 18 10 3–38 8 5 2–18

Note. MLCU = mean length of communication unit.
aLexical diversity reflects the number of different word roots produced in the language sample. bFluency reflects the percentage of
C-units with mazes. cIntelligibility reflects the percentage of unintelligible C-units.

Table 3. Amount of talk produced in conversation and narration.

Participant group n

Total C-units Complete and intelligible
C-units attempted

per minute

M SD Range M SD Range M SD Range

Conversation
Fragile X syndrome 27 126.04 39.22 65–202 107.07 36.93 42–187 12.79 3.85 6.50–20.20
Down syndrome 15 131.73 33.17 70–174 100.87 28.23 38–143 13.17 3.32 7.00–17.40
Typical development 15 107.33 25.64 70–148 95.60 23.25 61–140 11.03 2.86 7.50–16.80

Narration
Fragile X syndrome 27 43.56 16.89 21–76 36.41 13.09 19–60 11.32 4.27 4.30–22.14
Down syndrome 15 41.33 14.22 18–67 31.13 10.79 10–50 7.30 3.04 3.17–14.11
Typical development 15 39.87 10.07 20–56 34.93 10.41 17–52 8.65 2.61 4.48–12.81

Note. C-units = communication units.

Kover et al.: Context Effects 1029

but not significantly so (p = .151). Neither the effect of
context, F(1, 53) = 0.02, p = .900, nor the interaction,
F(2, 53) = 0.71, p = .495, was significant for intelligibility.

Variability Within Fragile
X Syndrome

We examined the impact of autism symptom sever-
ity on the amount of talk and language performance of
participants with fragile X syndrome (n = 26), control-
ling for nonverbal mental age. For each sampling con-
text, we entered autism severity and nonverbal mental
age into separate regressions predicting (a) the number
of complete and intelligible C-units, (b) the number of
C-unit attempts per minute, and (c) MLCU. We predicted
that autism symptom severity would negatively relate
to language production and, therefore, used one-tailed
p values for testing the regression coefficients in this
exploratory analysis; nondirectional p values were
used to test overall models. Unstandardized coefficients
are reported (see Table 5).

In conversation, autism severity scores were nega-
tively related to the number of complete and intelligible
C-units produced, controlling for nonverbal cognitive
ability (b = –4.36), t(23) = –2.02, p = .028, one-tailed,
semipartial r = –.37. The overall model predicting the
number of attempts per minute in conversation was
not significant (p = .079); however, severity scores did re-
late negatively to the number of attempts per minute,
controlling for nonverbal cognitive ability (b = –0.44),
t(23) = –1.91, p = .034, one-tailed, semipartial r = –.36.
Nonverbal cognitive ability was positively related to
MLCU in conversation (b = 0.92), t(23) = 2.53, p = .010,
one-tailed, semipartial r = .46; autism severity was not
(b = –0.07), t(23) = –0.81, p = .212, one-tailed.

In the narrative context, only the regression predict-
ing MLCU was significant (p = .007). As in conversation,
nonverbal mental age was positively related to MLCU
(b = 0.99), t(23) = 3.06, p = .003, one-tailed, semipartial
r = .52, whereas autism severity was not (b = –0.10),
t(23) = –1.30, p = .103, one-tailed. The overall models
predicting the number of complete and intelligible
C-units or the number of C-units attempted failed to
reach significance for narration (ps > .18).

Examiner Behavior
We examined the extent to which examiner behavior

was related to the language performance of participants
with fragile X syndrome using separate regressions for
conversation and narration. As a point of comparison,
we repeated these regressions for the adolescents with
Down syndrome and the boys with typical development.
Of course, these analyses cannot tease apart the direc-
tion of causation in the relationship between examiner
and child language, but they do provide guidance for
future research. Number of C-unit attempts per minute,
MLCU, and proportion of questions by the examiner
were all expected to be negatively related to amount
of participant language and performance (Kover,
Abbeduto, Schroeder, Giles, & Richmond, 2008). We
tested these three aspects of examiner behavior as
simultaneous predictors of participant language output
and performance using one-tailed p values. We chose
participant number of C-unit attempts per minute as a
dependent variable to index language output because it
reflects the clinical utility and efficiency of language
samples. We chose participant MLCU as a dependent
variable to index language performance because it is
widely used as an estimate of spoken language ability.

Table 5. Results of regressions for variability among participants with fragile X syndrome (n = 26).

Dependent variable

Full model

Individual predictors

NVMA Autism severity

F R2 b t b t

Conversation
Complete and intelligible C-units 3.48* .23 13.49 1.44 –4.36 –2.02y

C-units attempted per minute 2.84 .20 1.16 1.18 –0.44 –1.91y

MLCU 3.82* .25 0.92 2.53y –0.07 –0.81
Narration
Complete and intelligible C-units 1.85 .14 6.46 1.86y 0.57 0.71
C-units attempted per minute 1.25 .10 1.77 1.51 0.18 0.65
MLCU 6.11* .35 0.99 3.06y –0.10 –1.30

Note. NVMA = nonverbal mental age.

yp < .05, one-tailed. *p < .05.

1030 Journal of Speech, Language, and Hearing Research • Vol. 55 • 1022–1038 • August 2012

For conversation, the overall model predicting the
number of C-units attempted per minute was not signif-
icant for participants with fragile X syndrome (p = .080)
or Down syndrome (p = .151). The model was significant
for participants with typical development, F(3, 11) = 3.69,
p = .047, for whom examiner MLCU was significantly neg-
atively related to C-units per minute (b = –2.25), t(11) =
–2.46, p = .016, one-tailed, semipartial r = –.52 (see
Table 6). When predicting participant MLCU, the over-
all model was significant for participants with fragile
X syndrome, F(3, 23) = 11.67, p < .001, with examiner number of C-units per minute (b = –0.24), t(23) = –4.88, p < .001, one-tailed, semipartial r = –.64, and examiner MLCU (b = –0.66), t(23) = –3.01, p = .003, one-tailed, semipartial r = –.40, emerging as negative predictors (see Table 7). The model predicting MLCU was also signif- icant for typically developing participants, F(3, 11) = 5.67, p = .014, with only examiners’ number of C-unit attempts per minute negatively relating to MLCU (b = –0.26), t(11) = –1.83, p = .047, one-tailed, semipartial r = –.35. The over- all model predicting MLCU was not significant for par- ticipants with Down syndrome (p = .065).

For narration, the model predicting the number of
C-units per minute was significant for participants
with fragile X syndrome, F(3, 23) = 5.64, p = .005. A
higher proportion of questions asked by the examiner
was associated with fewer C-units per minute (b =
–0.26), t(23) = –4.10, p < .001, one-tailed, semipartial r = –.65. The models were not significant for participants with Down syndrome or typical development (ps > .18).
The model predicting MLCU was not significant for par-
ticipants with fragile X syndrome (p = .238), but it was
for participants with Down syndrome and typical de-
velopment, F(3, 11) = 6.99, p = .007; and, F(3, 11) =
3.77, p = .044, respectively. For participants with Down
syndrome, the number of attempts per minute by the

examiner was significantly associated with lower MLCU
(b = –0.50), t(11) = –3.69, p = .002, one-tailed, semipartial
r = –.65. For participants with typical development, exam-
iner MLCU was negatively related to MLCU (b = –0.44),
t(11) = –1.89, p = .043, one-tailed, semipartial r = –.40.

Discussion
In this study, we sought to examine the differential

effects of language-sampling context on the spontaneous
expressive language profiles of male adolescents with
fragile X syndrome and Down syndrome. The inclusion
of a comparison group of typically developing boys also
allowed conclusions to be drawn about the extent of
delay in each neurodevelopmental disability relative to
nonverbal cognitive ability.

Comparison of Fragile X Syndrome, Down
Syndrome, and Typical Development

Effects of context among groups. Performance on the
conversation and narration language-sampling tasks
was assessed in terms of the amount of talk produced
and in terms of language ability. Within both of these
areas, differential effects of context on performance
were found among participants with fragile X syndrome
(regardless of autism symptom severity), Down syn-
drome, and typical development, controlling for nonver-
bal mental age.

In terms of the amount of language produced, a sig-
nificant Group × Context interaction revealed that
adolescents with Down syndrome differed from both
adolescents with fragile X syndrome and boys with typ-
ical development in the number of C-units attempted per
minute in conversation relative to narration. Although all

Table 6. Aspects of examiner behavior as predictors of participant C-unit attempts per minute.

Participant group n
Full model
Individual predictors

Ex. attempts Ex. MLCU Ex. questions

F R2 b t b t b t

Conversation
Fragile X syndrome 27 2.56 .25 –0.09 –0.52 –1.75 –2.20y 0.03 0.34
Down syndrome 15 2.16 .37 0.56 2.10 0.08 0.06 –0.13 –1.44
Typical development 15 3.69* .50 –0.45 –1.23 –2.25 –2.46y 0.18 2.11

Narration
Fragile X syndrome 27 5.64* .42 0.08 0.26 0.65 1.14 –0.26 –4.10y

Down syndrome 15 0.77 .17 –0.29 –0.55 0.06 0.06 –0.10 –1.05
Typical development 15 1.94 .35 –0.01 –0.01 –0.75 –0.99 –0.07 –0.83

Note. Ex. = Examiner.
yp < .05, one-tailed. *p < .05.

Kover et al.: Context Effects 1031

groups tended to have higher rates of C-unit attempts in
conversation than narration, adolescents with Down
syndrome had particularly low rates of C-units at-
tempted per minute in the narrative context relative to
the conversation context. Adolescents with fragile X syn-
drome showed the smallest difference in number of
attempts per minute across contexts, but this effect did
not differ from the boys with typical development. Miller
(1996) has suggested that the amount of talking during a
language sample is an important quantifiable aspect of
performance that might reflect an individual’s linguistic
competence. Narration may be a particularly challeng-
ing task for adolescents with Down syndrome relative
to their nonverbal cognitive abilities and relative to
those with other sources of intellectual disability, such
as fragile X syndrome. Given the constraints and de-
mands of the content of the wordless book on the lan-
guage produced, we speculate that participants with
Down syndrome may have required additional process-
ing time in formulating their expressive responses,
leading to fewer C-units per minute. In contrast, the
demands of reciprocal social interaction in conversation
might be more of a challenge for adolescents with fragile
X syndrome, resulting in a smaller difference between
conversation and narration language production for
this population.

In terms of expressive language ability, the effect of
context on MLCU differed across groups. Relative to the
typically developing boys, for whom MLCU was similar
in conversation and narration, adolescents with fragile
X syndrome demonstrated higher MLCU in narration
than in conversation. Adolescents with Down syndrome
also produced higher MLCU in narration than conversa-
tion, although the comparison with boys with typical de-
velopment for the effect of context just failed to reach
significance. Previous studies have also suggested that
MLU elicited during narration tends to be higher than

conversation for adolescents and young adults with neu-
rodevelopmental disabilities, including fragile X syn-
drome, Down syndrome, and unspecified etiology
(Abbeduto et al., 1995; Kover & Abbeduto, 2010; Levy,
Gottesman, Borochowitz, Frydman, & Sagi, 2006;
Miles et al., 2006). The narrative task provides opportu-
nities to describe the actions and mental states of a pro-
tagonist in relation to other characters as well as to
linguistically encode event sequences, all of which are
best accomplished using multiclause constructions
(Heilmann, Nockerts, & Miller, 2010). The visual sup-
port of narrating a book also may allow production of
more advanced syntax (Levy et al., 2006). Miles and col-
leagues (2006), for example, found that MLCU for partic-
ipants with Down syndrome was higher in narratives
obtained using wordless picture books compared with
narratives embedded within an interview-style conver-
sation. Thus, our findings reinforce that narration is par-
ticularly well suited to eliciting the upper bounds of
syntactic ability in individuals with neurodevelopmen-
tal disabilities and that weaknesses might be more likely
identified in conversation samples, in which MLCU was
lower for participants with fragile X syndrome and Down
syndrome, than in narration, in which the discrepancy
between the groups with intellectual disability and typ-
ical development was minimized (Abbeduto et al., 1995).

There was also a differential effect of context across
groups for fluency, which was indexed by the proportion
of C-units with mazes (i.e., filled pauses and repetitions).
Fluency was found to be better (i.e., fewer mazes) in nar-
ration than conversation for typically developing boys,
relative to participants with Down syndrome who were
more fluent in conversation than narration. Adolescents
with fragile X syndrome showed comparable fluency ac-
ross contexts relative to the other groups. Research on
adolescents with Down syndrome and children with typ-
ical development has shown poorer fluency in conversation

Table 7. Aspects of examiner behavior as predictors of participant MLCU.

Participant group n
Full model
Individual predictors
Ex. attempts Ex. MLCU Ex. questions
F R2 b t b t b t

Conversation
Fragile X syndrome 27 11.67* .60 –0.24 –4.88y –0.66 –3.01y 0.01 0.29
Down syndrome 15 3.22 .47 –0.07 –1.12 0.19 0.62 –0.04 –1.98y

Typical development 15 5.67* .61 –0.26 –1.83y –0.16 –0.45 –0.02 –0.71
Narration
Fragile X syndrome 27 1.51 .17 –0.12 –1.04 –0.20 –0.90 –0.02 –0.65
Down syndrome 15 6.99* .66 –0.50 –3.69y –0.20 –0.81 –0.02 –0.84
Typical development 15 3.77* .51 –0.26 –1.69 –0.44 –1.89y 0.01 0.46

yp < .05, one-tailed. *p < .05.

1032 Journal of Speech, Language, and Hearing Research • Vol. 55 • 1022–1038 • August 2012

than narration (Miles et al., 2006), although some re-
search on children with language problems has indicated
the opposite (MacLachlan & Chapman, 1988; Wagner
et al., 2000). Becoming familiar with a story before nar-
rating likely leads to mental rehearsal, and thus a fluent
narrative, whereas the dynamic demands of conversation
decrease the opportunities to plan words and phrases in
advance (Kover & Abbeduto, 2010). The demands of the
narrative task relative to nonverbal cognitive ability for
adolescents with particular neurodevelopmental dis-
abilities, however, might outweigh the benefits of pre-
viewing a story, leading to particular difficulty with
fluency during narration.

The finding that fluency differed less between con-
versation and narration for participants with fragile
X syndrome relative to those with Down syndrome or
typical development is surprising, as one might expect
that the well-documented social anxiety associated with
fragile X syndrome would lead to poorer fluency in con-
versation. However, relative to the boys with typical de-
velopment, the adolescents with fragile X syndrome had
increased age and life experiences that may have sup-
ported performance in the conversation task. It is also
possible, however, that individuals with fragile X syn-
drome relied more on rote or repetitive (i.e., highly re-
hearsed) linguistic contributions, thereby reducing the
processing demands of the task. In fact, Roberts, Price,
et al. (2007) found that boys with fragile X syndrome had
more perseverative talk than typically developing chil-
dren and that boys with fragile X syndrome with comor-
bid ASD had more noncontingent talk than those with
fragile X syndrome only. Future research will need to an-
alyze the content of utterances produced by individuals
with fragile X syndrome in relation to the other aspects
of their language performance. Although the content
and form of communicative attempts might be appropri-
ate targets for intervention, producing those attempts
fluently appears to be a strength for adolescents with
fragile X syndrome.

Of the dimensions of performance examined, there
was one significant main effect of context. Participants
produced more C-units in conversation than in narra-
tion. These results are consistent with those of Abbeduto
et al. (1995), who studied youths with intellectual disabil-
ity of unspecified etiology. The context effect for the ab-
solute number of C-units might be accounted for simply
by the fact that the conversation sample was structured
to last at least 10 min, whereas the child had the option
to say as much or as little as he chose for each page of the
storybook in the narrative context. Because the number
of C-units attempted per minute also tended to be greater
in conversation than narration, these results suggest that
conversation is ideal for assessing some aspects of ex-
pressive language because of the increased likelihood
of efficiently eliciting a larger sample of utterances.

Taken together, the effects of context observed in the
present study for participants with fragile X syndrome
and Down syndrome highlight the need for language-
sampling procedures that include multiple structured
contexts to fully understand the profile of language
abilities in individuals or groups of individuals with
developmental disabilities (Abbeduto et al., 2012).
Although the ADOS has been recommended as one
structured context in which language can be sampled
(Tager-Flusberg et al., 2009), it is unknown whether
the ADOS provides a sufficiently consistent context
with stable expectations of language performance,
even for typically developing individuals. Given the dif-
ferential effects of context across diagnostic groups, one
might expect different conclusions to be drawn about
language abilities in neurodevelopmental disabilities
depending on the properties of the language-sampling
task.

Extent of delay in fragile X syndrome and Down syn-
drome. Several differences in performance emerged be-
tween adolescents with fragile X syndrome (irrespective
of autism symptoms) or Down syndrome and boys with
typical development, controlling for nonverbal mental age.

Adolescents with fragile X syndrome demonstrated
lower MLCU than typically developing boys, indicating
that syntactic complexity is an area of particular weak-
ness, as shown in previous studies (Roberts, Hennon,
et al., 2007). Participants with Down syndrome pro-
duced lower MLCU than both the boys with typical de-
velopment and the adolescents with fragile X syndrome.
Price et al. (2008) found the same pattern of results in a
younger sample of boys using the ADOS as a language-
sampling context: Participants with typical develop-
ment outperformed those with fragile X syndrome,
who outperformed those with Down syndrome. In a nar-
rative context, Finestack and Abbeduto (2010) found
that participants with fragile X syndrome without
comorbid autism also outperformed participants with
Down syndrome on a measure of overall grammatical
ability. Children with other neurodevelopmental dis-
abilities, including idiopathic autism, also have deficits
in MLU beyond nonverbal expectations (e.g., IQ; Eigsti,
Bennetto, & Dadlani, 2007), reinforcing the notion that
syntax should be a focus of intervention for a wide range
of children with neurodevelopmental disabilities. How-
ever, in agreement with findings of previous research,
the presentstudy demonstrates that syntactic complexity
is a syndrome-specific area of weakness in need of partic-
ular attention in adolescents with Down syndrome.

Lexical diversity also was found to be an area of weak-
ness for adolescents with fragile X syndrome or Down syn-
drome. Both groups of participants with intellectual
disability used a smaller range of vocabulary than the
boys with typical development, although participants
with fragile X syndrome and Down syndrome did not

Kover et al.: Context Effects 1033

differ. Although the interaction between context and
group failed to reach significance in the present study,
the impact of sampling context on lexical diversity
should continue to be considered in future research on
neurodevelopmental disabilities. Descriptively, partici-
pants with Down syndrome seem to use a particularly
restricted range of vocabulary during narration, and
previous studies have shown that conversation is more
likely than narration to assess the scope of vocabulary
available to a participant (Kover & Abbeduto, 2010).

Adolescents with fragile X syndrome or Down syn-
drome did not differ from boys with typical development
in fluency; however, those with fragile X syndrome pro-
duced a smaller proportion of C-units with mazes (i.e.,
were more fluent) compared with participants with
Down syndrome. In general, participants with fragile
X syndrome were the most fluent, which might be
expected if these participants were the most likely to
use repetitive (i.e., well-practiced) language. The overall
group difference between fragile X syndrome and Down
syndrome is likely driven by the particularly poor fluency
of the adolescents with Down syndrome during the nar-
rative task, suggesting a syndrome- and, to some extent,
context-specific area of weakness.

Participants with Down syndrome were less intel-
ligible than both participants with fragile X syndrome
and those with typical development. Problems with
intelligibility for individuals with Down syndrome have
been well documented in previous research, in which
even single-word production was impaired relative
to typically developing boys and boys with fragile
X syndrome with similar nonverbal cognitive abilities
(Roberts, Price, et al., 2007). The present results are
also generally in line with Barnes et al. (2009), who
found that boys with Down syndrome produced a smaller
percentage of intelligible words than those with typical
development; however, boys with fragile X syndrome
did not differ from those with Down syndrome in the
Barnes et al. study. In a sample of older adolescents,
Kover and Abbeduto (2010) also failed to find differences
between participants with Down syndrome and those
with fragile X syndrome with or without autism. The in-
consistent findings for differences in intelligibility be-
tween individuals with fragile X syndrome and Down
syndrome may be attributable to varying age ranges of
participants, procedures for assessing intelligibility, or
language-sampling contexts.

In summary, combining words into developmentally
progressive grammatical utterances and expanding
range of vocabulary are likely to be important interven-
tion targets for adolescents with fragile X syndrome. For
adolescents with Down syndrome, extending syntactic
complexity and vocabulary, in addition to enhancing flu-
ency and intelligibility during connected speech, are
likely to be areas in need of remediation.

Autism Symptom Severity
We examined the relationship between a continuous

metric of autism symptom severity in males with fragile
X syndrome and their language production in the con-
versation and narrative contexts, controlling for nonver-
bal mental age. Our results suggest that individuals
with more severe autism symptoms are less able to
engage with the demands of conversation, as reflected
in the production of fewer complete and intelligible
utterances. We found no relationship between autism
symptom severity and language production in narra-
tion; however, nonverbal cognitive level accounted for
variability in MLCU in both narration and conversation.
It seems reasonable that males with fragile X syndrome
who display more symptoms of autism could find the so-
cial demands of conversation more challenging given the
pressure to engage in a social give-and-take, whereas
engaging in the narrative task—and perhaps producing
grammatically complex utterances in general—is more
dependent on nonverbal cognitive skills. Producing con-
tingent talk in conversational contexts has been identi-
fied as an area of weakness for children with idiopathic
autism as well (Tager-Flusberg & Anderson, 1991).

Examiner Behavior
To our knowledge, no previous studies have exam-

ined the ways in which examiner behavior relates to
spontaneous language in youths with fragile X syndrome
or Down syndrome. Even within the constraints of our
structured procedures, relationships were found be-
tween variability in examiners’ talk and the language
performance of participants. In conversation, partici-
pants’ MLCU was negatively related to both examiner
MLCU and number of C-unit attempts per minute for
participants with fragile X syndrome and was related
to C-unit attempts per minute for participants with typ-
ical development. Examiner behavior was not related to
the performance of participants with Down syndrome
in conversation. In the narrative, number of C-unit
attempts per minute by participants with fragile X syn-
drome was negatively related to the examiner’s propor-
tion of questions, whereas MLCU for participants with
Down syndrome or typical development was negatively
predicted by examiners’ C-unit attempts per minute and
MLCU, respectively.

For a group of language-impaired children, Dethorne
and Channell (2007) interpreted correlations between
clinician behavior and child language as resulting from
the clinician adjusting her talk in relation to the talk
produced by the children. It would be expected that a
child who is reticent might elicit more coaxing from an
examiner, and the structure provided by the examiner
as an interlocutor should not be discounted. Similarly,

1034 Journal of Speech, Language, and Hearing Research • Vol. 55 • 1022–1038 • August 2012

the most likely explanation of our results is that the rela-
tionships observed reflect variability in response to the
language-sampling tasks by participants and the efforts
of the examiner to maintain participant engagement;
however, it is noteworthy that the pattern of relationships
varied across participants with fragile X syndrome, Down
syndrome, and typical development. Such relationships
should be taken into account in designing language-
sampling protocols that are flexible, yet structured, to
meet the needs of particular individuals and diagnostic
groups. Future research should probe the direction of
causality between examiner and child language.

Limitations
The results presented here are based on language

samples of relatively short duration and a relatively
small number of utterances. Although longer language
samples are in some ways ideal (e.g., 175 utterances;
Rice et al., 2010), there is evidence that shorter (e.g.,
3-min) language samples can provide reliable estimates
of language ability (Heilmann et al., 2010). In this sense,
the results are optimally interpretable from a clinical
perspective, given that it might be unrealistic to collect
larger language samples to assess youths with neurode-
velopmental disabilities in a clinical setting. This is par-
ticularly true for those with fragile X syndrome, for
whom inattentiveness or hyperactivity could impact
participation in assessment procedures. Nonetheless,
the fact that the language samples analyzed here
contained a limited number of utterances, particularly
for the narrative samples, should be considered in
terms of the generalizability of the findings. Only nine
participants with fragile X syndrome, four participants
with Down syndrome, and three participants with typi-
cal development produced 50 or more C-units during
narration. A potential advantage of the ADOS as a
language-sampling context is the likelihood of obtain-
ing a larger sample during the 30- to 60-min assessment.

The participants in the present study were limited
to those who scored within a restricted range of nonver-
bal cognitive ability, in order to allow simultaneous com-
parison of those with fragile X syndrome and typical
development, who tended to have higher developmental
levels, to those with Down syndrome, who tended to
have slightly lower developmental levels in the larger
sample from which these data are drawn. Having con-
trolled for nonverbal mental age, this analysis strategy
allowed for unambiguous interpretation of group differ-
ences within this developmental range but limits
the generalizability of the findings to other individuals
along the range of the highly variable phentoypes
of fragile X syndrome and Down syndrome. Investiga-
tion of the impact of sampling contexts on the language
of individuals with neurodevelopmental disabilities

across a range of nonverbal cognitive ability levels is
warranted.

Finally, the present study did not address the con-
tent of the utterances produced by participants in
terms of repetitiveness, perseveration, or contingency.
This will be an important area for future research, espe-
cially with respect to the impact of autism symptoms on
spontaneous expressive language in adolescents with
fragile X syndrome. Indeed, behavioral and pharmaceu-
tical interventions that seek to improve expressive lan-
guage in fragile X syndrome are likely to target not only
the amount of talk and the grammatical complexity of
that talk but also its communicative function by assess-
ing and documenting reduction in perseverative or non-
contingent utterances.

Conclusions
We have reported findings that draw attention to

the importance of considering the context in which lan-
guage samples are elicited for individuals with neurode-
velopmental disabilities. These results suggest that the
demands of the language-sampling context could have
implications for targets selected for intervention and
conclusions drawn about language profiles.

Acknowledgments
This work was supported by National Institutes of Health

(NIH) Grants R01 HD024356 and P30 HD003352, as well as
three fellowships awarded to the first author: the Waisman
Center’s Anderson Hoffman Wisconsin Distinguished Grad-
uate Fellowship, the Michael Vincent and Harriet Frisbie
Eastabrooks O’Shea Fellowship, and NIH F31 DC010959
National Research Service Award Individual Predoctoral
Fellowship. Portions of these data were presented at the
43rd Gatlinburg Conference on Research and Theory in Intel-
lectual and Developmental Disabilities in Annapolis, Maryland.
We offer our sincere appreciation to all of the families who par-
ticipated in this research. We thank Susen Schroeder for her
dedication in supervising the transcription of language samples
and Pamela Lewis for contributing to the autism evaluations.

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