Autism spectrum disorders (ASD) are developmental disabilities marked by severe deficits in reciprocal social interaction, communication, as well as repetitive and restricted patterns of interests and behavior (APA, 1994; Volkmar, Lord, Bailey, Schultz, & Klin, 2004). Children who qualify for diagnoses of ASD in the second year of life consistently demonstrate significant delay in the development of expressive language (Chawarska, Klin, Paul, & Volkmar, 2007; Chawarska & Volkmar, 2005; Paul, Chawarska, Cicchetti, & Volkmar, 2008; Wetherby, Watt, Morgan, & Shumway, 2006). Other studies of early vocal behavior in infant siblings of children with ASD (Landa & Garrett-Mayer, 2006; Landa, Holman, & Garrett-Mayer, 2007; Iverson & Wozniak, 2007; Zwaigenbaum, Bryson, Rogers, Roberts, Brian, & Szatmari, 2005) have reported both delays on standard tests of expressive language, and less mature syllable production (Dawson et al., 2000). In addition, several studies have shown that preschoolers with ASD produce higher levels of non-speech-like, atypical vocalizations than peers with typical development (Oller et al., 2010; Schoen et al., 2010; Sheinkopf, Mundy, Oller, & Steffens, 2000; Wetherby et al., 2006; Wetherby, Woods, Allen, Cleary, Dickinson & Lord, 2004).
Risk for ASD is known to be elevated in both parents and siblings of affected children (Bailey et al., 1995; Dawson, Estes, Munson, Schellenberg, Bernier & Abbott, 2007; Folstein & Rutter, 1977, 1988; Landa, Piven, Wzorek, Gayle, Chase, & Folstein, 1992; Piven, Palmer, Jacobi, Childress & Arndt, 1997; Santangelo & Folstein, 1999). In addition, Le Couteur, Bailey, Goode, Pickles, Robertson, and Gottesman (1996) found that, in twin pairs discordant for autism, concordance for language impairment and a broader autism phenotype (BAP) was much greater in monozygotic pairs than dizygotic pairs, consistent with a strong genetic component. Although definitions are still evolving, Micali, Chakrabarti, & Fombonne (2004) present a definition of BAP based on epidemiological findings, which includes social and communication impairments, as well as repetitive and stereotyped behaviors. Social abnormalities have been found to consist of impaired friendships, impaired social play, odd behavior and impaired conversation. Developmental language abnormalities are seen particularly in pragmatic language areas (Landa et al., 1992). Obsessional and repetitive behaviors can include circumscribed interests, rigidity, obsessions/compulsions and repetitive interests and activities. Micali et al. (2004) define BAP as a constellation of these abnormalities at a subthreshold level of severity that would qualify an individual for neither ASD nor another diagnosis, such as developmental delay or anxiety disorder.
Recent research on ASD has included ongoing monitoring of infants with an older sibling with ASD. This research focus stems from the literature reviewed above, which suggests that genetic factors play a significant role in the incidence of ASD (Bailey et al., 1995; Folstein & Rutter, 1988; Le Couteur et al., 1996; Rutter, 2005). In addition, awareness of risk for disorders associated with BAP, even in the absence of the full-blown syndrome (Szatmari et al., 2000), contributes to this trend. Studies documenting infant siblings’ development are aimed at earlier identification of these potential problems, and earlier provision of treatment in order to maximize outcome potential.
In the present report, we describe findings on early vocal behaviors in a group of infant siblings with this risk, and compare these behaviors to those of age-mates from low-risk families. In doing so, we would like to argue that the direct and detailed analysis of vocal behaviors in infants at risk for ASD will provide richer information than scores on standard tests, such as Mullen (1995), or than retrospective parent report of early vocal behavior. First, these analyses can tell us not only that high risk infants are delayed relative to peers, but also in precisely what aspects of prespeech behavior, whether it be the acquisition of specific consonants, syllable shapes, or prosodic contours. This level of detail may be illuminating in better understanding how the path to spoken language is affected in high risk infants. Second, although parents are sensitive to certain milestones of speech development (first canonical syllables [Oller, Eilers, Neal, & Cobo-Lewis, 1998], first words), they are not generally attuned to the specific consonants their children are using or the relative distribution of consonant and syllable types in infant production. Finally, retrospective parent reports, which have been used in other studies of early speech development (e.g., Gernbacher, Sauer, Geye, Schweigert, & Goldsmith, 2008) are subject to errors of recall and bias. By directly examining the maturity of prelinguistic vocalizations, we test the hypothesis that infant siblings of children with ASD will show precursors to delays in expressive language that are consistent with the development of ASD or BAP at higher rates than will low risk infants, and we examine the relation of these delays in the first year of life to the presence of autistic symptomotology in the second year.
Vocal Production in Typical Development
Oller, Eilers, Neal, & Schwartz (1999), Stark (1980), Stark, Bernstein, and Demorest (1993), and Locke (1993) have described the course of vocal development in the first year of life. Major milestones include:
- The appearance of first consonant-like productions in vocal play at 4-6 mo.
- The predictable expansion of the consonant repertoire; Shriberg (1993) classified the consonants of English into three groups, based on their typical order of acquisition in the first year (See Table 1).
- The emergence of canonical babble at 6-10 mo.; i.e., the use of consonant-vowel syllables with speech-like voice quality (Oller et al., 1999).
- The production of closed syllables (consonant-vowel-consonant) by the end of the first year of life (Leavitt & Utman, 1992).
Studies of typically developing children (e.g., Oller, Wieman, Doyle, & Ross, 1976; Schwartz & Leonard, 1982; Stoel-Gammon & Cooper, 1984; Vihman, Ferguson, & Elbert, 1986) have shown that canonical babble in the second half of the first year of life is generally continuous with the development of first sounds and words in speech, and babbling behavior at the end of the first year predicts later speech and language production in children with both typical development (Jensen, Boggild-Andersen, Schmidt, Ankerhus, & Hansen, 1988; Leonard, Schwartz, Morris, & Chapman, 1981; Menyuk, Liebergott, & Schultz, 1986; Stoel-Gammon, 1998; Storkel & Morrisette, 2002; Vihman & Greenlee, 1987) and those with delayed language (Paul & Jennings, 1992; Roberts, Rescorla, Giroux, & Stevens, 1998; Thal, Oroz, & McCaw, 1995). Thus investigating the development of pre-speech vocalization in the latter half of the first year may provide some insight into the transition to language in this population.
In the present report, we examine the forms of both speech-like and non-speech vocalizations in samples of infants at high and low risk for ASD, seen at 6, 9, and 12 months of age, using a cross-sectional design. In this way we aim to investigate the vocal tools children at risk for ASD are bringing to the task of learning to communicate. The following hypotheses will be tested:
- HR infants will produce fewer consonants and canonical syllable shapes, and more non-speech vocal behavior than LR peers;
- Less frequent and mature prespeech vocal behavior in HR infants during the first year of life will be associated with greater likelihood of the appearance of autistic symptomotology in the second year.