Despite the fact that humans are a highly social species, we know relatively little about how people remember the rich interpersonal information filling their social lives. This gap is surprising: One function of memory has been suggested to be relationship maintenance [Neisser, U. Time present and time past. Practical Aspects of Memory: Current Research and Issues , 2 , 545–560, 1988]. A major barrier to understanding the brain basis of interpersonal memory is that traditional brain imaging methods are not ideally suited to study memory for the nuanced interpersonal experiences comprising our social lives. Yet, recent and rapidly developing advances in the analysis of brain responses to naturalistic social information can help researchers surpass this methodological barrier. This perspective piece articulates the importance of studying the brain basis of real-world social memories and suggests new directions in interpersonal memory research. This includes investigating the brain mechanisms that represent the content and structure of real-world interpersonal memories as well as how they are altered in mental health conditions associated with social memory biases.

Social scientists have documented the power of being heard: Disclosing emotional experiences to others promotes mental and physical health. Yet, far less is known about how listeners digest the sensitive information people share with them. We combined brain imaging and text analysis methods with a naturalistic emotional disclosure paradigm to assess how listeners form memories of others' disclosures. Neural and linguistic evidence support the hypothesis that listeners consolidate memories for others' disclosures during rest after listening and that their ability to do so facilitates subsequently providing the speakers with support. In Study 1, brain imaging methods showed that functional connectivity between the dorsomedial subsystem of the default network and frontoparietal control network increased during rest after listening to others' disclosures and predicted subsequent memory for their experiences. Moreover, graph analytic methods demonstrated that the left anterior temporal lobe may function as a connector hub between these two networks when consolidating memory for disclosures. In Study 2, linguistic analyses revealed other-focused thought increased during rest after listening to others' disclosures and predicted not only memory for the information disclosed but also whether listeners supported the speakers the next day. Collectively, these findings point to the important role of memory consolidation during rest in helping listeners respond supportively to others' disclosures. In our increasingly busy lives, pausing to briefly rest may not only help us care for ourselves but also help us care for others.

Humans have a tendency to think about themselves. What generates this self-focus? One clue may come from the observation that the same part of the brain that supports self-reflection—the medial pFC (MPFC/Brodmann's area 10 [BA 10])—also spontaneously engages by default whenever the brain is free from external demands to attention. Here, we test the possibility that the default tendency to engage MPFC/BA 10 primes self-referential thinking. Participants underwent fMRI while alternating between brief periods of rest and experimental tasks in which they thought about their own traits, another person's traits, or another location's traits. Greater default engagement in MPFC/BA 10 during momentary breaks preferentially facilitated task performance on subsequent self-reflection trials on a moment-to-moment basis. These results suggest that reflexively engaging MPFC/BA 10 by default may nudge self-referential thinking, perhaps explaining why humans think about themselves so readily.

Humans readily adopt an intentional stance to other people, comprehending their behavior as guided by unobservable mental states such as belief, desire, and intention. We used fMRI in healthy adults to test the hypothesis that this stance is primed by the default mode of human brain function present when the mind is at rest. We report three findings that support this hypothesis. First, brain regions activated by actively adopting an intentional rather than nonintentional stance to a social stimulus were anatomically similar to those demonstrating default responses to fixation baseline in the same task. Second, moment-to-moment variation in default activity during fixation in the dorsomedial PFC was related to the ease with which participants applied an intentional—but not nonintentional—stance to a social stimulus presented moments later. Finally, individuals who showed stronger dorsomedial PFC activity at baseline in a separate task were generally more efficient when adopting the intentional stance and reported having greater social skills. These results identify a biological basis for the human tendency to adopt the intentional stance. More broadly, they suggest that the brain's default mode of function may have evolved, in part, as a response to life in a social world.