Fragile X syndrome

This study examined the communication and symbolic behavior profiles of 22 males with fragile X syndrome (FXS) developmentally younger than 28 months and the relationship of these profiles to the children's communication skills one year later. The boys, ranging in age from 21 to 77 months, were tested using the Communication and Symbolic Behavior Scales and the Reynell Developmental Language Scales. The children showed significant delays and substantial individual variability in their profiles. Overall, they showed relative strengths

in verbal and vocal communication and relative weaknesses in gestures, reciprocity, and symbolic play skills. Children who scored higher in communicative functions, vocalizations, verbalizations, and reciprocity scored higher in verbal comprehension one year later. Children with higher scores in verbal communication also scored higher in expressive language development when tested one year later.

Key Words: language assessment, mental retardation, fragile X syndrome, communication skills

Fragile X syndrome is the leading inherited cause of mental retardation in males, with an estimated prevalence rate of about 1 in 4,000 (Turner, Webb, Wake, & Robinson, 1996). In fragile X syndrome, there is an expanded number of Cytosine-Guanine-Guanine (CGG) nucleic acid repeats on a specific gene on one of the distal ends of the X chromosome. Affected individuals with more than 200 copies of the repeat sequence have a full mutation. The Fragile X Mental Retardation (FMR- 1) gene becomes methylated (i.e., shuts down) and does not produce FMR-1 protein, which is believed to affect brain functioning. Individuals who are carriers (premutation) have 50-200 CGG repeats and are generally not affected. However, the number of repeats may expand in successive generations. Individuals without fragile X have a range of 5-50 CGG repeats, with a mean of 29-30 repeats, and this number remains relatively stable across generations.

The majority of males with fragile X syndrome (FXS) have mental retardation, typically with mild to moderate deficits in childhood and moderate to severe deficits in adulthood (Hagerman, 1995; 1996). In addition to intellectual impairments, other physical and behavioral manifestations in males with FXS can include avoidance of eye contact, social withdrawal, limited attention span, hyperactivity, and autistic-like social deficits (Cohen et al., 1988; Cohen, Vietze, Sudhalter, Jenkins, & Brown, 1989; Hagerman, 1996). Males with FXS typically have communication deficits, although there is considerable variability in skills (Abbeduto & Hagerman, 1997; Benneto & Pennington, 1996; Dykens, Hodapp, & Leckman, 1994). Based primarily on studies of adolescents and adults, males with FXS have been described as having delays in grammar and vocabulary that are generally commensurate with their cognitive skills as well as "distinct" speech patterns with rapid or fluctuating rates, poor intelligibility in conversation, and frequent perseveration of words, sentences, and topics (Abbeduto & Hagerman, 1997; Dykens et al., 1994). The research on specific communication domains in adolescents and adults with FXS suggests a specific profile of communication. Misarticulations in single words are common among adolescent and adult males with FXS, although most have fairly good intelligibility in single words and poor intelligibility in conversational speech (Hanson, Jackson, & Hagerman, 1986; Newell, Sanborn, & Hagerman, 1983; Paul, Cohen, Breg, Watson, & Herman, 1984). Pragmatic skills generally are impaired in males with FXS, with frequent perseveration of words, sentences, or topics; poor topiomaintenance in conversation; gaze aversion; and inappropriate eye contact in interactions (Cohen et al., 1991; Dykens et al., 1994; Ferrier, Bashir, Meryash, Johnston, & Wolff, 1991; Hanson et al., 1986; Sudhalter, Cohen, Silverman, & Wolf-Schein, 1990). Semantic and syntactic delays occur, but it is unclear whether this delay represents a specific deficit in semantics or syntax. Scarborough and colleagues (1991) found that males with FXS who had a mean length of utterance above 3.0 used a narrow range of grammatical constructions while younger males did not exhibit this limitation. This seems to suggest a specific morphosyntactic difficulty in older males. Further, Sudhalter and colleagues (1992) found that males with FXS used a greater number of semantically incorrect words on a sentence completion task than did typically developing children of the same mental age.

The conclusions from these studies suggest that adolescent and adult males with FXS show delays in phonologic, syntactic, semantic, and pragmatic aspects of language. Specific deficits occur in pragmatic skills, speech intelligibility in conversational speech, and possibly, morphosyntax. These studies of speech and language primarily have been conducted with adolescents or adult males. Few of the studies examined the profiles of children's abilities across different communication domains. More importantly, only a small number of children younger than 8 years of age have been studied. It is unclear whether older preschool- and early elementaryage males with FXS show the same profile of communication skills as adolescent and adult males with FXS. Communication profiles could provide information about synchronies and asynchronies in development across domains and could help identify developmental strengths and gaps which would be useful in intervention planning. Mervis and Robinson (1999) recently recommended the use of domain profiles to examine specific aspects of communication within a particular syndrome. The literature on the communication development of young children in the last twenty years (Bates, Benigni, Bretherton, Camaioni, & Volterra, 1979; Bruner, 1977; Tomasello & Farrar, 1986; Wetherby, Cain, Yonclas, & Walker, 1988) has identified important aspects of communication in children under the age of two years, including: the functions of communication for behavior regulation, social interaction, and joint attention; the means of communication involving gestures, vocalizations, and verbalizations; the reciprocity of communication; the use of signaling, such as eye gaze, and displaying affect; and the role of symbolic behavior. Thus, one goal of this study was to describe the communication profiles of young males with FXS who are developmentally under 2 years old across communication domains.

The implications of specific early language profiles for later communication development are not entirely clear. For example, do young males with FXS who use language more frequently for behavior regulation, joint attention, and engagement in social interactions ultimately have higher levels of communication skills? Alternatively, do children who are less responsive and communicate less frequently continue to have lower levels of communication skills? Several studies have documented a relationship between early aspects of communication such as joint attention and phonological skills and later language development in children with autism, Down syndrome, mild mental retardation, and developmental delays (McCathren, Yoder, & Warren, 1999; Mundy, Sigman, & Kasari, 1994; Rollins & Snow, 1998; Sigman & Ruskin, 1999). A second goal of this study was to examine the relationship of early communication profiles to children's later communication skills. Defining profiles of early communication strengths and weaknesses would help identify important predictors of later developmental outcomes.

Purpose

The purpose of this study was to examine the communication profiles of preschool- and early elementary-age males with FXS, who were in the early stages of communication development. We were interested in examining a group profile for males with FXS across communication domains including communication functions, modes of communication, reciprocity, social affective signaling, and symbolic behaviors. We also were interested in examining the relationship of these profiles to children's communication skills one year later. The study children were participating in a longitudinal study of development and adaptive behavior of young males with FXS (Bailey et al., 1998). We previously reported on 39 young males with FXS ranging from 2 to 8 years old who demonstrated marked delays in language development as well as substantial individual variability (Roberts, Mirrett, & Burchinal, 2001). This cohort of males with FXS acquired expressive language skills more slowly than receptive language over time, and growth in language skills was related to initial developmental level and autism characteristics. The previous study examined only overall receptive and expressive communication and did not look at how specific communication domains predicted later communication development.

Method

Study Participants

The study participants were 22 males with a confirmed diagnosis of full mutation FXS. The children were recruited from a larger study that is examining the cognitive and adaptive behavior of young males with FXS (Bailey et al., 1998). Children younger than 7 years old who were referred from health professionals in five genetic clinics in Georgia, North Carolina, South Carolina, and Virginia were invited to participate. At the time of their first language assessment, the children ranged in age from 21 months to 77 months, with a mean age of 49.2 months (SD = 16.4). Nineteen of the children were white and three were African American. One family had two children participating. The educational levels of the children's mothers were reported as: 27.3% with a high school degree, 59.1 % with some college, and 13.6% with a graduate degree.

The 22 children were selected from the larger sample of children based on the following criteria. First, they had to have a diagnosis of full mutation FXS confirmed by blood sample analysis. Second, children had to have scores that were developmentally in the age range of the tests. That is, their receptive language skills had to be at or above 12 months and expressive language at or above 15 months, the respective basal age equivalents reported for the U.S. Edition normative sample on the Reynell Developmental Language Scales (Reynell; Reynell & Gruber, 1990). Additionally, each child had to score no higher than 28 months on the expressive section of the Reynell scales, because the Communication and Symbolic Behavior Scales (CSBS; Wetherby & Prizant, 1993) is appropriate for children whose language development falls between 8 and 24 months. Third, children were not included if they demonstrated features consistent with a diagnosis of autism indicated on the Childhood Autism Rating Scale (CARS; Schopler, Reichler, & Renner, 1988). We did not include young males with autism, because about 7-25% of individuals with FXS are also diagnosed with autism (Bailey, Hatton, & Skinner, 1998; Baumgardner, Reiss, Freund, & Abrams, 1995), and we were interested in defining a communication profile that was not influenced by the distinct profile characteristic of autism. Additionally, we had previously reported a relationship between children's communication skills and their autistic characteristics (Roberts et al., 2001).

All but one of the 22 of the children in the current study were participants in the earlier study of communication development (Roberts et al., 2001). Based on the language stages defined by the CSBS, 16 of these children were at a multiword stage of language development (having ten or more different words and two or more different word combinations); three children were at the late one-word stage (having 6 to 9 different words and less than 2 different word combinations); and three children were at the early one-word stage (having 2 to 5 different words and less than 2 different word combinations). Children's mean cognitive quotient, as measured by the Battelle Developmental Inventory (BDI; Newborg, Stock, Wnek, Guidubaldi, & Svinicki, 1984), was 55.8 (SD = 13.4). The BDI was administered as part of the larger Carolina Fragile X Project every 6 months during a separate assessment visit (Bailey et al., 1998). A mean quotient from all BDI cognitive tests was computed. See Bailey and colleagues (1998) and Roberts and colleagues (2001) for further details on the BDI scores.

Measures

Communication and Symbolic Behavior Scales (CSBS). The CSBS examines communication, social, and symbolic abilities of children developmentally between 8 months and 24 months old. A communication sample is elicited with both the examiner and caregiver present using communicative temptations and shared book reading, which are designed to encourage a child to communicate. Each temptation involves a toy or activity that is demonstrated by the examiner with minimal verbal commentary. For example, in the "bubbles temptation," the examiner begins by blowing bubbles; then the examiner hands the jar of bubbles to the child with lid closed and waits for the child to ask the examiner or his mother to blow more bubbles. In the symbolic play sample, the child plays with a doll or stuffed toy (e.g., Big Bird), using feeding and grooming sets; responds to language comprehension questions (e.g., about body parts, agents); and participates in constructive play activities (e.g., stacking rings). Each of the child's communicative acts are scored for multiple behaviors (e.g., function of the communication if a gesture, vocalization, or verbalization was used) and separate items are scored for symbolic behavior. Thus, the child's communicative and symbolic behavior is scored along 22 scales. Raw scores on each of the 22 scales are converted into a 1 to 5 scale with a I reflecting few instances of a behavior and 5 reflecting a high number of behaviors. For example, for behavior regulation, a rating of 1 is used for 0-3 behavior regulations, 2 for 4-18 behavior regulations, 3 for 19-31 behavior regulations, 4 for 32-42 behavior regulations, and 5 for more than 43 behavior regulations. The 22 scaled scores are then grouped to form seven communication clusters:

1. Communicative functions. Examines the use of gestures, sounds or words for behavior regulation (e.g., requests); joint attention (e.g., comment on object or action); and social interactions (e.g., showing off).

2. Gestural communicative means. Examines different conventional gestures (e.g., pushing away, shaking head), distal gestures where the child's hand does not touch a person or object while gesturing (e.g., waving, pointing at a distance), and coordination of gestures with vocalizations.

3. Vocal communicative means. Includes the use of vocalizations, different syllables with consonants, and multisyllables (vowel only or vowel plus consonant).

4. Verbal communicative means. Includes the total number of different words and different multiword combinations used by the child.

5. Reciprocity. Includes behaviors to maintain the topic or forms; the number of communicative acts produced per minute during the test; and the child's use of repair strategies to modify or repeat a previous communication attempt when a goal is not achieved.

6. Social-affective signaling. Examines the use of gaze shifts between a person and an object and the expression of positive and negative affect.

7. Symbolic behavior. Measures the child's ability to understand and respond to simple directions in context ("point to your eyes"); the number and complexity of different logical action schemes acted out in symbolic play; and the level of constructive play (e.g., reassembling nesting cups).

The norming sample for the CSBS was 282 typically developing children from 8 to 24 months and 30 children with developmental disabilities from 18 to 30 months. Adequate levels of reliability (internal consistency coefficient was .91, median interrater reliability coefficient was .90) and high levels of validity (content, criterion, and construct) were reported in the normed edition of the CSBS manual (Wetherby & Prizant, 1993). Few gender differences were evident in the normative sample, particularly for children under 15 months old. Additionally, the manual reported that the CSBS correctly classified 85% of children with pervasive developmental disorders and 60% of children with speech-language impairment.

The protocol for coding and scoring the CSBS for the 22 study children followed the procedures in the CSBS. Two assistants coded the CSBS after reaching a high level of agreement on a criterion tape of three children. The criterion videotape was produced by the CSBS developers to train the coders in their CSBS standardization study. Reliability was computed for each of the categories in each communicative act for six of the study children. Intercoder reliability was calculated using intraclass correlations (Winer, 1971), which takes into accounts the dependencies in the data. Intercoder reliability was .74.

Reynell Developmental Language Scales (Reynell). The Reynell measures verbal comprehension and expressive language skills of children developmentally between 1 and 7 years old. The Verbal Comprehension Scale measures the development of receptive language skill, from the recognition of sound and word patterns to the understanding of complex language. The Expressive Language Scale examines the acquisition of structure and syntax, knowledge of words and their representation, and the ability to verbalize connected ideas about a familiar situation. The U.S. version of this originally British test was standardized on 619 American children from 1 to 7 years of age. Reliability estimates for the Reynell-US edition are high (median split-half reliability coefficient of .87). The Reynell demonstrates good content, construct, concurrent and predictive validity, although most of the validity data reported in the manual are based on the British edition. Age levels were computed for the Verbal Comprehension Scale (VCA) and the Expressive Language Scale (ECA).

Procedure for testing. The Reynell and the CSBS were administered by one certified speech-language pathologist (SLP) in the child's home as part of a battery of tests that included other measures of speech and language. The CSBS was administered to all children at the first session. The Reynell was administered to all children at the first session and to 19 of the 22 children one year later. All sessions were audiotaped and videotaped. The Reynell videotape was reviewed for reference when responses were unclear or additional information was needed. To establish procedural reliability, three videotapes were reviewed. The SLP administered 94.2% of the time the required prompts for the CSBS and 97% of the time the required prompts for the Reynell.

Data Analysis

Means and standard deviations were computed for the raw scores and scaled scores for the 22 CSBS scales. The mean of the scaled scores composing each cluster was averaged and a mean and standard deviation were computed for each of the seven clusters: communicative functions, gestural communicative means, vocal communicative means, verbal communicative means, reciprocity, social-affective signaling, and symbolic behavior. We examined children's communication profiles using the mean scaled scores across the seven domains. Next, we used Pearson's correlations to examine the intercorrelations among the seven CSBS cluster means. Then, we ran Pearson's correlations to determine the relationship between the seven CSBS cluster scores and the following: children's age, BDI scores, and concurrent measures of VCA and ECA on the Reynell. We looked at each child's age and BDI scores, because a child age and cognitive level frequently are related to one's communication. Finally, we examined Pearson's correlations to assess whether there was a relationship between the CSBS, as a predictor, and children's receptive and expressive communication one year later, after partialing out the child's age.

Results

Communication Domains

Table 1 shows the means for the raw and scaled scores for the 22 CSBS scales, and the averaged scaled scores for the seven CSBS clusters (mean of scaled scores composing each cluster). The scaled scores are developmental standard scores that range from 1 to 5, with a mean of three and a standard deviation of one. The mean scaled score indicates how much the sample differs from norms based on typically developing children 8 to 24 months old. Scores less than 3 generally indicate an earlier stage of development and scores above 3 generally indicate a later stage of development within the 8 to 24 month period. We could not compute standard or percentile scores for the clusters, because the children were chronologically older than the age range of the test.

Examining the mean scaled scores for each of the seven clusters, children scored highest on verbal communication (4.3) and in vocal communication (4.0). Children scored approximately one-half standard deviation (.5 point) lower in gestural communication (3.4), symbolic behavior (3.5), and reciprocity (3.5). The majority of children, about 70 percent, had scores on verbal communication more than one-half standard deviation (.5 point) higher than gestural communication, signaling, symbolic behavior, and reciprocity. Forty percent of the sample had verbal scores one standard deviation (1 point) or more than gestural communication, signaling, reciprocity, and symbolic behavior. For the remaining 30% of the children, there was considerable variability, with some children showing the opposite pattern. For example, one child had close to one standard deviation higher score in gestural communication and reciprocity than in verbal communication and another had close to a standard deviation higher in gestural communication and signaling than in verbal communication. Similar results were found for differences in scores between vocal communication and gestural communication, signaling, symbolic behavior, and reciprocity. Children's mean communicative function scaled score of 3.7 was less than one-half standard deviation from the other cluster scaled scores, except for verbal communication.

Examination of the specific scaled scores within each cluster revealed additional differences in communication skills. Children's strengths were evident in their verbal and vocal scores for different words, different word combinations, different consonants, syllables containing consonants, and gestures with vocalizations. In the socialaffective signaling cluster, children scored high on alternating gaze shifts between person and objects and in negative affect. In contrast, children's mean scores were over one standard deviation lower in the use of conventional and distal gestures, expression of positive affect, complexity of action schemes, and repair strategies. Children's use of communication for behavior regulation and joint attention, sociability of communication, rate of communication, responsiveness, and other aspects of symbolic behavior were less than one-half standard deviation higher or lower than the scaled scores of the other 22 items. On all scaled scores, there was considerable variability as shown by an examination of the standard deviations.

Correlations Among CSBS Domains

Table 2 shows that the mean scaled scores were generally moderately or highly interrelated, except for social affective signaling. The other scales showed significantly positive correlations with each other (r = .47 to .92), while social affective signaling did not significantly correlate with the other measures (r = .03 to .18).

Correlations for CSBS Domains and Child's Age, Cognitive Skills, and Concurrent Measures of Language

Next we wanted to determine if children's chronological age or cognitive level could be responsible for differences in children's scores on the CSBS clusters during the first assessment. Table 3 presents children's ages at the time of the CSBS assessment, which was, on average, 49.2 months. There was a significant positive relationship between children's chronological age and several domains, with children who were older scoring higher on communication functions (r = .55; p = .08), vocalizations (r = .66; p = .0009), verbalizations (r = .75; p = .0001), and symbolic behavior (r = .53; p = .0119). None of the communication domains were significantly correlated with children's BDI quotient scores.

Next, we looked at the relationship between CSBS scaled scores and concurrent measures of receptive and expressive language on the Reynell. Children's chronological age was, on average, 49.2 months, and they typically had a VCA of 22.2 months and an ECA of 21.6 months. (See Table 3). Table 4 shows the correlations between the CSBS scaled scores and the Reynell VCA and ECA administered at the same time point. Children who had higher verbal comprehension (VCA) scored higher on communication functions, vocalizations, verbalizations, and reciprocity (r = .45-.59). Children who had higher expressive language (ECA) scored higher on all measures (r = .53-.89), except social affective signaling.

Using CSBS Domains to Predict Children's Later Communication Skills

Next, we examined partial correlations between the CSBS scores and children's expressive and receptive language on the Reynell one year after the administration of the CSBS, partialing out children's chronological age. Children were on average 64.3 months chronologically, but had substantially lower communication ages of 30.7 months for VCA and 28 months for ECA. (See Table 4 for the Reynell scores and the correlations.) Only 19 children were included in this analysis because three children did not have Reynell data at the second assessment. Children who had higher CSBS scores on communicative functions, vocalizations, verbalizations and reciprocity scored higher in verbal comprehension on the Reynell one year later. Children who had more verbalizations on the CSBS scored higher in expressive language development on the Reynell one year later.

Discussion

Males younger than 8 years old with FXS demonstrated significant delays in their overall communication performance, as well as substantial individual differences in their communication profiles. Overall, the communication profiles showed that young males with FXS had relative strengths in verbal and vocal communication and relative weaknesses in gesturing, reciprocity, and symbolic behaviors. Specific strengths were evident in the use of different words, word combinations, and sounds, and in the use of gaze shifts. Specific weaknesses occurred in the use of repair strategies, conventional gestures (e.g., pushing away), distal gestures (pointing at a distance), and complex action schemes. This profile of relative strengths and weaknesses was not consistent for all children. Furthermore, children who scored higher in communicative functions, vocalizations, verbalizations, and reciprocity scored higher in verbal comprehension one year later. Similarly, children who had higher scores in verbal communication on the CSBS scored higher in expressive language development one year later. Although relative strengths and weaknesses were evident in the profiles of the young males with FXS, communication skills in general were delayed considerably.

Examination of the seven CSBS cluster scores revealed a profile of relative strengths and weaknesses. Males with FXS who were developmentally in their second or third years of life showed relative strengths in their use of verbalization and vocalizations and relative weaknesses in gesturing, reciprocity, and symbolic behavior. It must be noted that the cluster scores were generally similar (ranging from 3.4 for gestural communication means to 4.3 for verbal communication means). The mean differences between these strengths and weaknesses were, for the most part, only .5 of a scale point, or one-half of one standard deviation. According to the CSBS developers (Wetherby & Prizant, 1993), a large difference would be 1 standard deviation or greater. Only the difference between gestural communication and verbal means was close to one standard deviation. However, when we looked at the data from individual children, over 40% of children did show a standard deviation difference between both verbal and vocal communication and gestural communication, symbolic behavior, and reciprocity. Thus, these differences of relative strengths and weaknesses should be interpreted carefully.

The 22 individual scales further specify the strengths and weaknesses in the profiles of young males with FXS. On scales that involved verbal communication and vocal communication, young males scored similarly high on the use of different words, word combinations, and sounds, and on the use of gestures with vocalizations. Scores on the social/communicative measures involving regulation of behavior, joint attention, social interaction and two of the reciprocity measures (i.e., rate of communicating and respondent acts) were similar in not revealing strengths nor weaknesses. However, one aspect of reciprocity-use of repair strategies-was a relative weakness. Within social affective signaling, gaze shifts and negative affect were strengths, while positive affect was a relative weakness. For gestures, both conventional and distal gestures were weaknesses, while the use of gestures involving a vocalization was a strength. Within symbolic behavior, complexity of action schemes was weak relative to the other aspects of symbolic behavior.

Young males with FXS in this study had some skills consistent with reports in the literature of the communication skills described for older males with FXS, but many skills were not. Unlike older adolescents and adult males (Cohen et al., 1988; 1991; Sudhalter et al., 1990), younger males with FXS in this study appeared to be more skilled in certain social aspects of communication relative to other aspects of communication. The males with FXS participating in this study were relatively skilled in behavior regulation, joint attention, and responding to communication using a frequent number of gaze shifts for social referencing during social interactions. It was particularly interesting that strengths in gaze shifts were apparent, given the frequent reports of gaze avoidance and difficulty with mutual eye contact among older males with FXS (Cohen et al., 1988; 1989; Wolf, Gardner, Paccia, & Lappen, 1989). However, when Wolf and colleagues (1989) studied six young males with FXS between 4 and 7 years of age and one male at 1 year of age, they found that the infant and five of the six children showed no gaze aversion. Also, gaze shifts, as defined by the CSBS, might not have the same communicative intent as the gaze avoidance used in the other studies of older males with FXS. The definition of gaze shifts in the CSBS required that eye gaze be directed toward an adult's face and that it alternate between a person and an object, and back again. This definition differed from the gaze avoidance characteristic of older males with FXS, which required shared attention and the child's returning the gaze. One possibility is that the frequent gaze shifts among our study children could have been used as ways to gain information about the communication interactions with the adults by using concrete visual aspects of the communication context.

These young males with FXS, however, did show relative weaknesses in two social communicative aspects of behavior-repair strategies and positive affect. Repair strategies involve the ability to repeat or modify a signal when a goal is not obtained. The child needed to recognize that a communication breakdown had occurred, that the communication might be successful if he were to try again, and then to produce another response by either repeating or modifying his communication. This involved a sophisticated processing of social cues that may be an early index of social and communication skills (Wetherby, Alexander, & Prizant, 1998) and might relate to later pragmatic difficulties in older males with FXS. Positive affect involved a shared affective state of pleasure and may also contribute to later difficulties in the social interactions of young males with FXS. On the other hand, the lack of positive affect in this study could have been in response to some of the toys used during the CSBS (e.g., toys in a bag, blocks in the box), which might not elicit the same positive affect in a 6-year-old that they would in a typically developing 2-year-old.

The young males with FXS also displayed lower scores in the use of gestures, both conventional and distal, and in symbolic behavior skills. Lower scores in gestures may be related to delays in the development of symbolic representational skills (Thai & Tobias, 1992). Their symbolic behavior, particularly in complexity of action schemes as compared to different action schemes, suggests an ability to demonstrate the basic function of items in symbolic play, but difficulty combining items in a series or sequence of related symbolic play routines. This may be suggestive of underlying cognitive difficulties in young males with FXS, particularly with sequencing, imitation, use of tools, or symbolic representation. Another explanation for the lower scores in gestures may be due to difficulties in visual motor skills and motor planning similar to those experienced by older males with FXS (Bennetto & Pennington, 1996; Freund & Reiss, 1991; Hodapp et al., 1992; Kemper, Hagerman, & Altshul-Stark, 1988). Lower scores in gesture may also be due to the study children possibly relying on vocal/verbal means of communication instead of gestures. They may have gone beyond use of gestures to communicate using more often vocal and verbal means instead.

It is difficult to say whether the findings in this study suggest that young males with FXS who are developmentally younger than 2 years old show delays in their communication rather than atypical communication development. Overall we did not see large differences across communication domains; the mean differences between domains were generally only half of a standard deviation, although many children did show larger differences between vocal or verbal behavior and gestures, reciprocity, and symbolic behavior. Larger mean differences among the cluster scores would be much more suggestive of atypical language patterns. Additionally, the moderate level of correlations among the CSBS cluster scores and the finding that social affective signaling did not correlate with other communication domains were similar to the data reported on the CSBS for typically developing children in a one-word and multiword stage of language development (Roberts, Medley, Swartzfager, & Neebe, 1997; Wetherby & Prizant, 1993). Thus, these correlational data also suggest that the patterns of the relationship between the domains were similar to typically developing children and not atypical. These findings also suggest that social affective signaling may be a factor independent of the other communicative and symbolic measures. Strengths or weaknesses in the communication and symbolic domains did not reflect similar patterns in social affective signaling. However it is possible that the lack of correlation between social affective signaling and the other communication measures is due to scoring social affective signaling on a separate pass from the scoring of communication functions and gestures, vocal and verbal communication, and reciprocity. Yet, symbolic behavior is also scored totally separately and was related to these other communication measures.

It is also interesting that the communication profiles of the young males with FXS in this study who did not have co-occurring autism differed from the descriptions in the literature of children with autism, with whom males with FXS are compared. Children with autism show pervasive deficits in joint attention, social-affective signaling, and sociability of communication (Mundy, Sigman, & Kasari, 1994; Sigman & Ruskin, 1999; Wetherby, Prizant, & Hutchinson, 1998). The young males with FXS in this study did not show deficits relative to other skills in social communication areas, although the relative difficulties with repair strategies and, possibly, positive affect do indicate some possible social communicative difficulties.

A second purpose of this study was to examine the relationship between children's communication profiles and their later receptive and expressive language development. We found that children who scored higher in communicative functions, vocalizations, verbalizations, and in reciprocity during the first assessment generally had higher scores in verbal comprehension one year later. Only verbal communication was predictive of expressive communication one year later. This finding may be explained by the overlap of verbal behaviors on both the CSBS verbal communication and the Reynell expressive communication. The study findings that early social and communication behavior predict later language development are similar to studies (McCathren et al., 1999; Rollins & Snow, 1998; Sigman & Ruskin, 1999) that have found a relationship between specific aspects of early communicative skills and later development of receptive and expressive communication skills. These findings also lend support to the importance of early social and communicative behavior for children's later language development.

This study had several limitations that must be considered in interpreting the findings. First, the sample size was only 22 young males with FXS, and they were seen only one or two times. Larger samples of children with FXS, studied using repeated assessments over a longer period of time, would help further define communication profiles. Such a study could also examine communication subtypes and the role of other important factors such as maternal interaction style and interventions in affecting the growth of children's communications skills. Additional children would provide more power to detect different profiles and distinguish between associations that were moderate to large in degree and those that were spurious. Second, although the study children varied greatly in chronological age, they were restricted in the developmental level of their communication-most were iq the multiword stage of language development and the remaining few were at a one-word stage. (All children were in the developmental age range of both the Reynell and the CSBS.) Therefore generalizing these data to males with FXS at other stages of language development is not possible; generalization should also be done cautiously for males at the one-word stage, because of the small number of children at that stage in this study. Third, the CSBS was designed to elicit communication from children developmentally less than 2 years of age. Some of the toys were more appropriate for children younger than those in this study and may have affected children's interactions. Finally, the intercoder reliability using intraclass correlations was a little low at .74. However, this was due in part to the restricted variance in scores for some of the CSBS categories.

Despite such limitations, these study results are important. Using a prospective study design, this study provides much needed information across multiple domains of social and communication skills of young males with FXS who were developmentally younger than 2 years old. This preliminary study provides some support for a profile of strengths and weaknesses across language domains in young males with FXS as well as a broad spectrum of individual variation in the very early stages of language acquisition. If future studies continue to support these profiles, then these specific strengths and weaknesses should be examined carefully in the assessment of young males with FXS and targeted in intervention. The findings also highlight the importance of early social and communicative behavior for affecting later communication skills among young males with FXS. We plan to continue to follow the study children to further define a communication phenotype for fragile X syndrome and examine how these communication profiles affect later communication development for males with FXS.

Acknowledgments

This research was supported by the National Institute on Disability and Rehabilitative Research, U.S. Department of Education, H133G60186-97, and the National Institute of Child Health and Human Development, 1 R01 HD 38819-01 and 1 R03 HD 40640-01. We first want to express our thanks to the children and families who participated in this study. We also want to express our special thanks to Dr. Donald Bailey and Dr. Deborah Hatton for sharing their BDI data and for their support of this project. We have greatly appreciated the help of Ms. Shaye Benton, Ms. Shani Levine, and Ms. Clare Norins in assisting with data collection. We also thank Ms. Sarah Henderson for her assistance in manuscript preparation.

References

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Received March 29, 2001 Accepted November 21, 2001

DOI: 10.1044/1058-0360(2002/034)

Joanne E. Roberts*

Penny Mirrett

Kathleen Anderson

Margaret Burchinal**

Eloise Neebe

Frank Porter Graham Child Development Center University of North Carolina at Chapel Hill

*Also affiliated with Department of Pediatrics and Division of Speech and Hearing Sciences, Department of Allied Health Sciences

**Also affiliated with Department of Psychology

Contact author: Joanne E. Roberts, PhD, Frank Porter Graham Child Development Institute, University of North Carolina at Chapel Hill, 105 Smith Level Road, CB# 8180, Chapel Hill, NC 27599-8180. E-mail: joanne-roberts@unc.edu

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