Project BABEE was a longitudinal project that followed infant development from birth to age three and sought to explore the factors that influence infant temperament and how these early temperamental tendencies impact relationships with caregivers and peers. We used various research methods, including questionnaires, naturalistic observations (in the home), saliva samples, and interviews to determine how nature and nurture influence early social and emotional development. Saliva samples allowed us to measure hormonal changes in the infant that occurred in reaction to the environment.