Friendship=similar neural responses
Humans are exceptionally social creatures. Neuroscientists are now mapping social networks onto brain networks.
Social network characterization.
The social network of a first-year cohort of Masters of Business Administration (MBA) students was reconstructed based on responses to online questionnaires administered to all members of the class 5–6 months after they had first met (N = 275; 99.3% response rate). Nodes indicate students; lines indicate reported social ties between them. For ease of visualization, only mutually reported social ties are illustrated. A subset of these students participated in an fMRI study conducted 8–9 months after they had first met one another. Orange nodes indicate fMRI study participants (N = 21); grey nodes denote other members of the graduate program. Node size is proportional to eigenvector centrality.
Definitions
viewing individuals who varied in terms of "degrees of separation" from themselves (social distance), the extent to which they are well connected to other well-connected individuals (eigenvector centrality) and the extent to which they are connected to otherwise unconnected individuals (bokerage).
Ferguson, Niall. The Square and the Tower: Networks and Power, from the Freemasons to Facebook (p. xi). Penguin Publishing Group. Kindle Edition.
Geodesic social distance refers to the minimum number of intermediary social ties required to connect two individuals.
Eigenvector centrality is a prestige-based centrality metric that considers not only how many connections a given individual has, but also the centralities characterizing each contact. High eigenvector centrality (high EC) implies that an individual is well-connected to well-connected others.
NATURE HUMAN BEHAVIOUR 1, 0072 (2017) | DOI: 10.1038/s41562-017-0072
J B. Silk, S. C. Alberts, J. Altmann, Science 302, 1231 (2003).
To probe for the spontaneous encoding of social network position information, the researchers used representational similarity analysis (RSA), which distills fMRI response patterns into representational dissimilarity matrices (RDMs) that indicate the degree to which particular brain regions distinguish between sets of stimuli or mental states.
Social network proximity appears to be significantly associated with neural response similarity in brain regions involved in attentional allocation, narrative interpretation, and affective responding may be exceptionally similar in how they attend to, interpret, and emotionally react to their surroundings.
NATURE COMMUNICATIONS | (2018) 9:332
During the fMRI study, each subject watched the same collection of video clips. The videos presented in the fMRI study covered a range of genres (comedy, documentaries, debates, etc.) that were selected so that rhey would likely be unfamilir to subjects, effectively cconsyrain subjects' thoughts and attention to the experient (to minimize mind-wandering), and evoke meaningful variability in responses across subjects (because different subjects attend to different aspects of them, have different emotional responses to them, or interpret the content differently).
Average dyadic fMRI response time series similarities overlaid on a cortical surface model (a lateral view; b medial view; c ventral view). . In order to illustrate how relative similarities of responses in each brain region varied as a function of social distance, inter-subject time series similarities.inter-subject time series similarities are computed.
Do we become friends with people who respond to the environment similarly, or do we come to respond to the world similarly to our friends? Although the results of the current study suggest that friends have exceptionally similar neural responses to naturalistic stimuli, due to this study’s cross-sectional nature, we cannot ascertain, based on these results alone, whether neural response similarity is a cause or consequence of friendship.
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