Atypical Cry Acoustics in 6-Month-Old Infants at Risk for Autism Spectrum Disorder

This study tested whether infants at risk for autism spectrum disorders (autism or ASDs) show differences in vocal production in early infancy by examining whether infant siblings of children with autism showed alterations in acoustic properties of infant cries at 6 months of age. A common focus of early infant studies of autism has been on aspects of social responses and relatedness in early development. Findings have revealed that disruptions in social behaviors by 12 months, including poor response to name, atypical eye contact, and reduced social interest and social smiling, distinguish at-risk babies who are later diagnosed with autism [Zwaigenbaum et al., 2005]. Some studies have found alterations in social responses during the face-to-face/still-face procedure as early as 4–6 months of age, including fewer smiles directed at mothers [Cassel et al., 2007], diminished gaze to eyes relative to mouth [Merin, Young, Ozonoff, & Rogers, 2007], and less interactional synchrony between babies and mothers [Yirmiya et al., 2006]. However, in general, it has been difficult to identify robust deficits in social behaviors associated with autism in early infancy [Ozonoff et al., 2010]. However, other atypicalities seen in childhood autism may also be investigated in infancy. For example, atypical vocal production has been studied in toddlers and young children with autism [Oller et al., 2010; Schoen, Paul, & Chawarska, 2011; Sheinkopf, Mundy, Oller, & Steffens, 2000; Woods & Wetherby, 2003]. These studies have found that autism is associated with atypical vocal quality and that such vocal parameters may help to discriminate children with or at risk for a diagnosis. Such findings lead to the prediction that differences in infant vocal production may be evident in babies at risk for or later diagnosed with autism. Recently, Paul, Fuerst, Ramsay, Chawarska, and Klin, [2010] reported that infants at risk for autism produce lower rates of canonical syllables by 9 months but not at 6 months of age. Because this capacity to produce well-formed babbles is just emerging in early infancy, age-specific findings may reflect a floor effect for the sensitivity of phonological structure to detect differences between risk groups at young ages. Nonsegmental aspects of vocal production may be more sensitive to differences associated with autism in early infancy. Infant cries are one type of nonsegmental production that can be observed from the earliest days of life. Cry acoustics have been studied in other clinical and at-risk populations, and may be disrupted in infants at risk for autism. Esposito and Venuti [2009, 2010] have reported differences in observer ratings of cry at 12 months of age in later-diagnosed babies from home videotapes. Observers rated the cries of infants later diagnosed with autism as having more atypical features and fewer prototypical cry patterns than babies with typical development and those with developmental delays [Esposito & Venuti, 2009]. These researchers also reported higher fundamental frequency (F0) of cries in later-diagnosed infants vs. typically developing infants by 12 months of age [Esposito & Venuti, 2010]. Differences in infant cry acoustics have not yet been found in relation to autism earlier in development. The production of cry is the result of air being forced through the vocal tract and over the larynx. Vibrations of the vocal folds result in the sound that is perceived by humans as crying. This sound can be described with a variety of parameters, including the loudness or amplitude of the cry, the timing of cry onset, and length of interutterance intervals. Other aspects of cries can be represented acoustically by describing features such as F0, voicing, and formant frequencies. F0 is the base frequency of a cry and is perceived as pitch. Voicing, also called phonation, describes cry sounds resulting from harmonic vibration of the vocal folds. Formants (e.g. F1, F2, etc.) describe additional resonant frequencies in the sound spectrum, and in speech recognition, work can be used to describe the configuration of the vocal tract. There is a long history of research on infant crying in populations considered at risk for developmental differences, as well as those with identified conditions [Karelitz & Fisichelli, 1962; Prechtl, Theorell, Gramsbergen, & Lind, 1969; Wasz-Hockert, Lind, Vourenkoski, Partanen, & Valanne, 1968]. This research includes more recent work describing acoustic features of infant crying in relation to risk for poor developmental outcomes [Gibbins et al., 2008; Goberman & Robb, 1999; Quick, Robb, & Woodward, 2009; Zeskind, Platzman, Coles, & Schuetze, 1996]. These results include differences in F0 and, to some degree, other measures of vocal tract configuration (i.e. formants) in infants with perinatal risks or medical complications such as hyperbilirubinemia, prenatal substance exposure, lead exposure, or frank evidence of brain damage [see LaGasse, Neal, & Lester, 2005]. Thus, cry characteristics are an indication of neurobehavioral risk. However, crying can also be understood in the context of a biosocial model, where infant crying is seen as both a physiologic event and part of a dyadic communication system between baby and caregivers [Lester, 1984]. In relation to autism, cry acoustics may reflect underlying neurobehavioral differences associated with the disorder and may also reflect differences in the development of the parent-infant dyad as well as being predictive of long-term developmental outcome [Lester, 1987]. Research in clinical populations has tended to focus on differences in average and maximum values of F0, range or variability of F0 across cry utterances, and other measures used to describe the acoustic characteristics of cries. However, other research, especially work in typical populations, has examined features that can be described as reflecting prosodic aspects of cry sounds. Work on cry prosody focuses on aspects such as the contour of cry pitch [i.e. nonlinear changes in F0 across an utterance; see, for example, Mampe, Friederici, Christophe, & Wermke, 2009 and Wermke, Mende, Manfredi, & Bruscaglioni, 2002]. Studies of prosodic features of cry may have value in the study of infants at risk for autism given the overall delays in language, and the differences in prosodic speech characteristics are often characteristics of children and adults with autism [Tager-Flusberg, 2005]. However, in order to be consistent with prior research linking cry characteristics with perinatal risks and poor developmental outcomes, the current study examines measures of cry utterance characteristics such as the average value and variability in F0, as well as measures of voicing in relation to risk for autism. This level of analysis is consistent with prior research on vocal characteristics of young children with autism. For example, research has found that young children with autism produce vocalizations with less clear emotional signals [Ricks & Wing, 1975], higher rates of atypical vocalizations [Wetherby et al., 2004; Wetherby, Yonclas, & Bryan, 1989], and with atypical voicing described as highly tense or high-pitched [Sheinkopf et al., 2000]. In an acoustic framework, these vocalizations could be characterized as having high overall F0 and unusual phonation or voicing. In the study reported in this paper, our aim was to investigate acoustic features of cries that may be linked to arousal, regulation, and neurobehavioral integrity. As such, overall descriptions of features such as F0 and phonation (voicing) were the focus of this study. We report initial findings of an investigation of cry production in a group of infants at risk for autism and a low-risk (LR) comparison sample. Prior findings from young children with autism and the limited number of observations of infants later diagnosed with autism led to the prediction that autism-related cry atypicalities will be found in the acoustic features of F0 and phonation, representing the degree to which cries are voiced. Differences in the amplitude or force of cry may also be present but are more difficult to operationalize because of measurement and recording difficulties.