This research will investigate whether birth mode shapes social behavior in childhood and adolescence. Cesarean delivery results in the newborn being exposed to lower levels of several important hormones than newborns delivered vaginally. These same hormones are known to shape social behavior throughout development, which leads us to hypothesize that birth is an important time for the developing brain. Disrupting hormonal signaling at birth via cesarean delivery is thus likely to impact the newborn's development.

Levels of each of the ‘birth signaling hormones’: oxytocin, arginine vasopressin, epinephrine, norepinephrine, and the glucocorticoids are lower following delivery by cesarean section compared to vaginal delivery, and there is substantial evidence for each of these hormones that manipulations in early life results in long-term neurodevelopmental consequences. This set of hormones has been extensively studied for their various roles in regulating social behavior in humans and non-human animals, often in a developmental context such as this, where manipulating their levels in early life alters social behavior throughout the rest of development. Furthermore, epidemiological associations have linked cesarean delivery with increased risk of autism spectrum disorder diagnosis and delayed social skills in early childhood. Finally, premature delivery is associated with markedly diminished rates of romantic attachment and sexual behavior. Thus, through multiple lines of evidence, we arrive at the central hypothesis: that birth mode can shape social behavior throughout the rest of life.