Date on Master's Thesis/Doctoral Dissertation

8-2017

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Psychological and Brain Sciences

Degree Program

Clinical Psychology, PhD

Committee Chair

Mervis, Carolyn B.

Committee Member

Woodruff-Borden, Janet

Committee Member

Cashon, Cara H.

Committee Member

Salmon, Paul

Committee Member

Davis, Deborah W.

Abstract

Children of a given age vary widely in their expressive vocabulary abilities. One factor that is related to child expressive vocabulary ability is the style in which the mother interacts with her child. Studies that have considered this relation for either typically-developing (TD) children or children with developmental or intellectual disability (DD/ID) (e.g., autism spectrum disorder, fragile X syndrome) have shown that children whose mothers have a more sensitive/responsive interaction style have significantly larger expressive vocabularies than do children whose parents have a less sensitive/responsive style (e.g., Baker et al., 2010; Belsky et al., 2007; Brady et al., 2014; NICHD Early Child Care Research Network, 2003). In this dissertation, I provide the first examination of relations between child expressive vocabulary, child chronological age (CA), child nonverbal reasoning IQ, estimated annual family income, and maternal interaction style for young children with Williams syndrome (WS). The hypothesis of the study was that child expressive vocabulary ability relative to TD peers would be predicted by maternal interaction style beyond the effect of child nonverbal reasoning ability relative to TD peers. Participants were 75 children (35 girls, 40 boys) with classic WS deletions aged 4.01 – 8.39 years. Median estimated family income was $120,000 (IQR: $70,000 - $200,000). Children completed the Differential Ability Scales-II (DAS-II; mean Nonverbal Reasoning Cluster standard score (SS): 79.4, SD: 14.8) and the Expressive Vocabulary Test-2 (EVT-2; mean SS: 81.6, SD: 16.5). In addition, each mother-child dyad participated in a 30-minute play session with developmentally appropriate toys. Play sessions were videotaped. The mothers’ behavior during the play sessions was coded from the video-recordings using three scales from the NICHD Early Child Care Research Network: Supportive Presence, Respect for Child Autonomy, and Hostility (reversed). A 7-point Likert scale was used for each scale, with higher scores indicating more responsive maternal interaction. As in previous studies (e.g., Belsky et al., 2007; Downer & Pianta, 2006; NICHD Early Child Care Research Network, 2003), a composite of these ratings was used to evaluate maternal interaction style. The median maternal interaction style composite score was 16.0 (range: 10.5 – 21.0). To examine relations between child expressive vocabulary, child CA, child nonverbal reasoning SS, estimated annual family income, and maternal interaction style composite bivariate nonparametric correlations were computed. The maternal interaction style composite was moderately positively correlated with EVT-2 SS (rs = .42, p < .001) and DAS-II Nonverbal Reasoning Cluster SS (rs = .42, p < .001). EVT-2 SS was strongly positively correlated with DAS-II Nonverbal Reasoning Cluster SS (rs = .62, p< .001). Estimated annual family income and child CA were not significantly correlated with any of the study variables (Mdn p-values = .849 and .382, respectively). To test the study hypothesis, sequential-model multiple regression analysis was performed. Model 1 was comprised of child CA, estimated annual family income, and DAS-II Nonverbal Reasoning Cluster SS. Maternal interaction style composite was added in Model 2. Model 2 provided a significantly better fit to the data than did Model 1, accounting for 43.4% of the variance in EVT-2 SS. Child CA and estimated family income were not significant predictors of child EVT-2 SS (ps> .5). Maternal interaction style composite and DAS-II Nonverbal Reasoning Cluster SS were significant predictors of child EVT-2 SS (p = .02 and p < .001, respectively). These results support the hypothesis that maternal interaction style significantly predicts child expressive vocabulary SS in children with Williams syndrome aged 4– 8 years even after taking into account the effects of nonverbal reasoning SS, estimated annual family income, and child CA. Implications for clinical interventions to facilitate more positive parent-child interactions are discussed.

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