Substantial neuroimaging evidence suggests that spontaneous engagement of the default network impairs performance on tasks requiring executive control. We investigated whether this impairment depends on the congruence between executive control demands and internal mentation. We hypothesized that activation of the default network might enhance performance on an executive control task if control processes engage long-term memory representations that are supported by the default network. Using fMRI, we scanned 36 healthy young adult humans on a novel two-back task requiring working memory for famous and anonymous faces. In this task, participants (1) matched anonymous faces interleaved with anonymous face, (2) matched anonymous faces interleaved with a famous face, or (3) matched a famous faces interleaved with an anonymous face. As predicted, we observed a facilitation effect when matching famous faces, compared with anonymous faces. We also observed greater activation of the default network during these famous face-matching trials. The results suggest that activation of the default network can contribute to task performance during an externally directed executive control task. Our findings provide evidence that successful activation of the default network in a contextually relevant manner facilitates goal-directed cognition.

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One can never know the internal workings of another person—one can only infer others' mental states based on external cues. In contrast, each person has direct access to the contents of their own mind. Here, we test the hypothesis that this privileged access shapes the way people represent internal mental experiences, such that they represent their own mental states more distinctly than the states of others. Across four studies, participants considered their own and others' mental states; analyses measured the distinctiveness of mental state representations. Two fMRI studies used representational similarity analyses to demonstrate that the social brain manifests more distinct activity patterns when thinking about one's own states vs. others'. Two behavioral studies complement these findings, and demonstrate that people differentiate between states less as social distance increases. Together, these results suggest that we represent our own mind with greater granularity than the minds of others.

Humans are highly social. We spend most of our time interacting with the social world and we spend most of our thoughts thinking about the social world. Are we social beings by default, or is our sociality a response to the social world? On the one hand, fundamental social needs may drive social behavior. According to this account, social thoughts fulfill social needs when the environment is insufficiently social. On the other hand, spontaneous thoughts may process incoming information. According to this account, social thoughts reflect the social information in the environment. To arbitrate between these possibilities, we assessed the content of spontaneous thought during mind wandering in three social contexts: solitude (Study 1), social presence (Study 2), and social interaction (Study 3). Additionally, in Study 1, we used functional neuroimaging to measure neural activity while participants considered social and non-social targets. Results consistently showed that spontaneous thought reflects the sociality of the world around us: Solitude decreased spontaneous social thought and decreased neural activity in the mentalizing network when thinking about a close friend. Social presence did not change spontaneous social thought. Social interaction increased spontaneous social thought. Finally, individual differences analyses (Study 4) showed that people in more social environments have more social thoughts. Together, the results show a pattern of increasing social thought in increasingly social environments. The predominance of social content in spontaneous thought can thus be explained by the predominance of social content in the world around us, rather than our innate, fundamental social needs.