Project Summary Original 5-year Project: The effectiveness of social buffering in regulating stress appears to wane for a period with puberty at the same time that stress-reactivity increases and young adolescents become more vulnerable to stress-related affective pathology. There is a dearth of knowledge regarding the neural underpinnings of social buffering in children and the changes with puberty. Two of the proposed experiments address this gap in knowledge. In addition, the loss of social buffering effectiveness with puberty has been examined using cortisol as the stress measure. All three proposed experiments will examine the pervasiveness of the effect by examining autonomic, in addition to cortisol measures. Finally, the effectiveness of social buffers during the peripubertal period has only been examined for social evaluative stressors. The proposed experiments will also examine whether the loss of social buffering also extends to threat stimuli and to situations in which two friends are both experiencing the stressful event together. Participants will be 11-14 years old and Tanner staging by parent- and self-report will index pubertal status. Our prior research uncovered the waning of the effectiveness of parents to serve as social buffers of the HPA axis over the pubertal transition and the concomitant failure of friends to “step in” as stress buffers. The proposed experiments are the logical extension of this work. The results will have the potential to drive significant attention to the role of developmental disruptions in social stress buffering as possible contributing factors in the rise of affective problems in the early teen years. Administrative Supplement: Two of the studies have been completed, a third study not proposed in the original application [administratively approved] was conducted during the COVID-19 lockdown to create an on-line version of the social evaluative stressor task to allow continued data collection for the non-imaging study. The two imaging studies were shutdown and then severely hampered during the pandemic. We are, thus, delayed in completing data collection and pre-processing for the 2nd imaging study. The supplement will allow us to complete the work initially proposed.