Fig. 2.

Results of correlational analysis and MLR analysis. (A) Correlations of acoustic parameter SVI/SCU ratio scores with age across the 1,486 recordings. In 10 of 12 cases, both typically developing and language-delayed children showed higher absolute values of correlations with age than children with autism (SI Appendix, Table S9 A–F). All 12 correlations for the typically developing sample and seven of 12 for the language-delayed sample were statistically significant after Bonferroni correction (P < 0.004). The autistic sample, conversely, showed little evidence of development on the parameters; all correlations of acoustic parameters with age were lower than ±0.2. (B) MLR for typically developing and autism samples. Blue dots represent real and predicted age (i.e., “predicted vocal development age”) for 802 recordings of typically developing children based on SVI/SCU ratios for the 12 acoustic parameters (r = 0.762, R² = 0.581). Red dots represent 351 recordings of children with autism, for which predicted vocal development ages (r = 0.175, R² = 0.031) were determined based on the typically developing MLR model. Each red diamond represents the mean predicted vocal development level across recordings for one of the 77 children with autism. (C) MLR for the typically developing (blue) and language-delayed samples (333 recordings; gold squares for 49 individual child averages; r = 0.594, R² = 0.353).