1. CONCLUSION There was a significant main effect of dyadic gender composition on dyadic tie strength, such that same-gender dyads demonstrated stronger ties than did mixed-gender dyads. The effects of dyadic similarity on problem behavior and social engagement on dyadic tie strength varied according to dyadic gender composition. Dyadic similarity on problem behavior was associated with greater tie strength for FF dyads and MF dyads, but not for MM dyads. Dyadic similarity on social engagement was associated with greater tie strength for mixed-gender dyads, but not for same-gender dyads. In general, behavioral similarity has more impact on dyadic tie strength for mixed-sex dyads than for same-sex dyads. INTRODUCTION When children enter a classroom, they must make choices about which peers to allocate their time and attention to. Similarity is thought to bring children together whereas dissimilarity is thought to push them apart. Children tend to spend more time with same-gender peers than with other-gender peers (Fabes, Martin, & Hanish, 2003). They also tend to spend more time with peers who share behavioral qualities, such as problem behaviors and social engagement, than they do with peers who differ on these behavioral dimensions (Hanish, et al., 2005). However, multiple dimensions of similarity are rarely studied simultaneously, raising questions about whether behavioral similarity matters equally for male dyads, female dyads, or mixed-gender dyads. PRESENT STUDY We created a measure of dyadic tie strength by calculating the amount of time children spent with each classroom peer over the academic year. Peer dyads were classified as male-male (MM), female-female (FF), and male-female (MF). For each peer dyad, we assessed similarity on two behavioral dimensions: problem behaviors and social engagement. HYPOTHESES We hypothesized that dyads who were more similar to one another on gender and on measures of problem behaviors and social engagement would have stronger ties. We also hypothesized that the gender composition of the dyad would moderate the relation of behavioral similarity to tie strength. The Strength of Children's Peer Relationships: The Role of Gender and Behavioral Similarity Sherri Castle 1, Laura D. Hanish 1, Hélène Barcelo 2, Burcu Eke 3, Jacob White 2, & Joseph Blitzstein 4 1 School of Social and Family Dynamics, Arizona State University; 2 Mathematical Sciences Research Institute; 3 Universidad Carlos III de Madrid; 4 Harvard University METHODS Participants 298 preschoolers (53% boys, 78% Mexican American, M age = 52 Months) attending 18 Head Start classes. Resulted in 5,228 dyads: 1,498 MM; 1,050 FF; and 2,680 MF Measures Dyadic Tie Strength: Peer interactions were recorded using a 10 second scan observation protocol (Martin & Fabes, 2001) Using the Q-Connectivity method (Hanish et al., 2008), we calculated dyadic tie strength, operationalized as the number of days a given dyad was observed interacting over the course of the academic year. Thus, higher scores represent greater tie strength. Dyadic similarity on Problem Behavior and Social Engagement Classroom observers rated children on Problem Behavior and Social Engagement (n = 7 and 4 items; α =.92 and.75, respectively). Dyadic similarity on each construct was calculated by taking the difference of the two children’s scores and recoding them such that larger scores indicate greater similarity ANALYSIS Modeling Strategy Multilevel Poisson regressions Three level model (L1: dyads, L2: children, L3: classrooms) Modeling Specification Dependent variable = Dyadic Tie Strength Predictor variables Initial tie strength (covariate) Gender composition of dyad (dummy codes for MM, FF, and MF dyads) Dyadic behavioral similarity (problem behavior and social engagement modeled separately) Interaction of gender composition of dyad and behavioral similarity DESCRIPTIVES For more information, please contact Laura Hanish at laura.hanish@asu.edu This project was funded by Grant DA025218-01 to Hélène Barcelo and Laura D. Hanish. Data used in this study were collected in a project funded by Grant HD045816-01 to Carol Lynn Martin, Richard A. Fabes, and Laura D. Hanish. RESULTS Fixed Effect Predictors of Dyadic Tie Strength Predictor Problem Behavior β Social Engagement β Initial tie strength0.10***0.11*** MM dyads1.60***2.82*** FF dyads1.81***2.90*** MF dyads1.42***2.58*** Similarity0.15***0.12*** MM*Similarity0.040.01 FF*Similarity0.11**-0.06 *p <.05. **p <.01. ***p <.001.