The primary vocal registers of modal, falsetto, and fry have been studied in adults but not per se in infancy. The vocal ligament is thought to play a critical role in the modal-falsetto contrast but is still developing during infancy (Tateya and Tateya, 2015). Cover tissues are also implicated in the modal-fry contrast, but the low fundamental frequency (f) cutoff of 70 Hz, shared between genders, suggests a psychoacoustic basis for the contrast. Buder, Chorna, Oller, and Robinson (2008) used the labels of "loft," "modal," and "pulse" for distinct vibratory regimes that appear to be identifiable based on spectrographic inspection of harmonic structure and auditory judgments in infants, but this work did not supply acoustic measurements to verify which of these nominally labeled regimes resembled adult registers. In this report, we identify clear transitions between registers within infant vocalizations and measure these registers and their transitions for f and relative harmonic amplitudes (H1-H2). By selectively sampling first-year vocalizations, this manuscript quantifies acoustic patterns that correspond to vocal fold vibration types not previously cataloged in infancy. Results support a developmental basis for vocal registers, revealing that a well-developed ligament is not needed for loft-modal quality shifts as seen in harmonic amplitude measures. Results also reveal that a distinctively pulsatile register can occur in infants at a much higher f than expected on psychoacoustic grounds. Overall results are consistent with cover tissues in infancy that are, for vibratory purposes, highly compliant and readily detached.

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Early social interaction lays the foundation for developing language skills. Maternal depression may affect social interaction by disrupting the temporal structure of turn-taking. In this study, we examine the temporal properties of dialogue extracted from video recordings of semi-structured play between mothers and preschool children enrolled in the Early Head Start Research and Evaluation Program (n = 110). Our preliminary analyses examine how higher levels of maternal depression (on the CES-D scale) are related to the number and duration of utterances, the number of conversational turns, and the latency and variability of responses for both the mother and the child. The primary goal of the study is understanding how depression impacts bidirectional processes in mother-child interaction, and the quality of children's early language experience.

Turn-taking in dialogue is an essential part of communication and early language experience. The prevalence of utterances and the timing of responses in dialogue were examined at 14 and 36 months of age in 104 mother-child dyads from the Early Head Start Research and Evaluation Project (EHSREP). Mothers varied in their level of depression risk (measured with the Center for Epidemiological Studies-Depression scale; CES-D). Although maternal utterance rate did not vary significantly across any factors, the latency of mothers' responses to their children decreased with development (12 ms/month) and was significantly related to that of their own children (i.e., slowresponding children had slow-responding mothers). Mothers with higher levels of depressive symptoms were 11% slower in responding to their children than mothers with low depression risk, suggesting that the interactive timing of speech to children may be particularly sensitive to maternal depression, modifying the contingent properties of children's early language experience. K E Y W O R D S depression, Early Head Start, mother-child dialogue, turn-taking 1 | MATERNAL DEPRESSION AND THE TIMING OF MOTHER-CHILD DIALOGUEThe back-and-forth turn-taking pattern of dialogue is highly structured, precisely timed, and depends on a variety of processes that allow individuals to perceive, interpret, formulate, and execute speech (Levinson & Torreira, 2015;