Project Summary Investigating the neural bases of social behavior is critical for our understanding of complex, high-level cognition. Despite recent efforts to examine complex social cognition on a neural level, there are still many questions left unanswered. One prominent question is whether internal states typically associated with motivation and arousal can also be found in social domains. Internal states are indexed by continuous neural activity patterns that fluctuate over time and reliably predict specific behaviors. So far, internal states predictive of social behavior, known as social states, have only been shown in flies and mice. These results are foundational for the study of social states but cannot speak to complex social behaviors found in other species. Nonhuman primates exhibit some of the richest social behaviors that are likely guided by social states. Preliminary data in our lab shows that specific neural states predict social gaze during dyadic social interactions and expressing social preferences in macaques. This early evidence supports future endeavors in characterizing primate social states, including those described in this proposal. Internal states are often impacted by external environmental factors. For social states, this may include incoming social information from the environment such as visual or auditory communication from conspecifics. Such states may also be systematically affected by prosocial and antagonistic communication. However, whether social states are systematically influenced by social environmental information, and are therefore vulnerable to manipulation, is unknown. It is also unknown what regions of the brain may be implicated in social states. A prime candidate region for investigating this question is the basolateral amygdala (BLA), an area known for its broad involvement in social cognition and internal states. This proposal introduces the overarching hypothesis that social behaviors are driven by internal states and are vulnerable to changes by external social stimuli. In Aim 1 I will investigate whether visual and auditory stimuli carrying specific social information (‘social stimulus conditioning’) impacts specific behaviors involving social attention and perception. Potential impacts by social stimulus conditioning will be evaluated across two behavioral paradigms and provide knowledge on whether social states are generalized. In Aim 2, I will expand this research to include neural investigations of social states including possible involvement of the BLA. Neural states predicting specific social behaviors will be characterized through machine learning approaches. This will be the first study to compare social stimulus conditioning and social state induction in nonhuman primates. Overall, this proposal will address novel questions of primate social states and further our understanding of neural mechanisms underlying complex social behavior.