Project summary/Abstract The rewarding bonds we forge in adulthood, in particular our pair bonds with romantic partners, have innumerable protective effects on our brains and behaviors. Individuals with difficulties in social engagement and competence, such as those suffering from social anxiety, major depression, ADHD, or Autism Spectrum Disorder, are particularly susceptible to the health risks of social isolation and impoverished social networks. Aberrant activity of dopaminergic reward systems during adolescence coincides with the onset of many of these disorders, suggesting that developmental abnormalities in the neural substrates that promote social reward underlies disease pathology. Critically, most of what we know about the neural mechanisms that facilitate pair bonding come from the study of adult brains, highlighting a dire need to investigate the functional development of social bonding circuits to design better therapeutic treatments for social dysfunctions. The current proposal aims to leverage the socially monogamous prairie vole system to investigate the maturational changes in dopaminergic reward circuitry that initiate the capacity for pair bonding in adulthood. Prairie voles form strong pair bonds with their mates, which relies on the functional activity of dopamine systems. In Aim 1, I will use fiber photometry to ask how developmental age and sex mediates socially induced changes in in vivo dopaminergic neural activity. In Aim 2, I will use chemogenetic approaches to investigate how perturbing dopamine circuits during sensitive developmental periods impacts adult pair bonding phenotypes. Finally, in Aim 3 I will investigate the developmental changes in transcriptional signatures of same‐sex and opposite‐sex social interactions as prairie voles mature and become capable of dopamine‐dependent pair bonding. Altogether, these efforts will determine how social experiences across developmental time scaffold the maturation of pair bonding dopamine circuits. These findings will profer novel insights into the molecular and cellular processes that may be disrupted in neuropsychiatric illnesses involving impaired bonding behaviors, which cannot be investigated in traditional non‐bonding rodent models.