A Study of Vocalization and Mother-Infant Interactions on the Emergence of Sex-Related Differences During Infancy Carmen Jimenez-Robbins, Christelle Ngnoumen, Richard Ahl, Brian Schmidt, Elizabeth Boghossian, Alexandra Toth, Mary Zeng, Anne Fausto-Sterling, Cynthia Garcia Coll, Deborah Schooler, Ronald Seifer, and Jihyun Sung Brown University, Providence, RI. April 2009 Introduction Past studies have found that: Female infants and toddlers have higher rates of vocalizing and higher scores on tests of language production and comprehension. Mothers of females vocalize more to their infants than mothers of males. However, most of these studies: Have not taken a contextual approach (i.e. what mothers do while vocalizing to their infants) Have not illuminated the sources of these differences (i.e. “innate,” based on parental behavior, etc.) Have not yet incorporated State Space Grid software in the study of dyadic interactions Have not employed Dynamic Systems Theory Results For both frequency and duration of infant vocalization, no main effect for sex was found. Mothers used significantly more total speech to female infants during 3-6 months and 7-10 months (p<.01), while mothers babbled significantly more to male infants during 7-10 months and 11-14 months (p<.05) (See Table 1). Mothers of male infants engaged in more physical stimulation while vocalizing during 7-10 months and 11-14 months (p<.05) (See Table 2). When solely examining aggregate vocalization rates, mothers engaged in more speech with female infants. However, when examining the co-occurrence of maternal vocalization and physical stimulation, mothers of male infants engaged in more physical stimulation while vocalizing during 7-10 months and 11-14 months. This suggests that future research should take a deeper look at cross-systems interactions, such as what physical behaviors mothers engage in while vocalizing with their infants. Due to our small sample size, our findings must be interpreted as preliminary. Aim Following the Dynamic Systems framework, our aim is to study longitudinal, naturalistic observations of mother-infant dyads. We will focus on the simultaneous occurrence of vocalization and motor stimulation with special attention to sex-related differences. Method Participants: 4 infants between the ages of 3 and 14 months 2 females, 2 males White, middle-class RI. families (SES range of 1 to 3) First-time, married mothers. None were working full-time during their child’s first year. Mean maternal age on infant’s date of birth= 29 Procedure: Naturalistic observations of playtogether scenarios were taped in the families’ homes (Seifer, et al., 1994). We then coded them on a second-by-second basis using Noldus Observer XT. Weekly data was divided into the following three age groups for analysis of developmental trends: 3-6 months 7-10 months 11-14 months. Moment-by-moment dyadic interactions were analyzed using State Space Grids (SSG) software and SPSS.