Statistical Analysis

SPSS software (IBM Analytics, Armonk, New York) was used for statistical analysis. Intraclass correlation coefficients (ICC) were used to determine inter-rater reliability for analyzing calls. To assess the effects of age (in days) on acoustic parameters (listed above), mixed model linear regressions were performed. Sex was not considered as a variable due to difficulty differentiating individuals from a mixed sex twin pair, and sexual dimorphism is not evident in marmosets [10]. Separate models were created for each call parameter. Each model was evaluated with a fixed effect for age and a random effect with separate slopes for subject. Assumptions of linearity, normality, homoscedasticity, and collinearity were assessed prior to running the models. A criterion reference of α < 0.05 was used to represent statistical significance.