In Sync?

The title of this study (see citation below), Emotions promote social interaction by synchronizing brain activity across individuals, might be misleading to some. It is not about telepathy! It is not about some sort of rhythms or physical vibes! It is about people reacting in similar ways to the same emotional signal – not a surprise, emotional signs are, after all, an important part of communication between people.


But the paper is also about what areas of the brain are active in various emotional and arousing situations. It has an informative contrast between of valence and arousal.

Our results thus demonstrate that valence and arousal have distinct roles in synchronizing brain activity—and possibly also behavior—across individuals. These opposite effects on ISC (intersubject correlation) fit with the proposed distinction between valence and arousal representations in the brain and they also highlight the neurobehavioral functions that emotional arousal and valence may have in human social interaction. The key mechanisms that may support similar emotional processing across individuals are automatic and spatially similar focusing of attention toward emotion-laden stimuli and the subsequent mapping of others’ emotional states in the body and brain. Our data suggest that the attention-related mechanism is arousal-contingent, whereas the mapping mechanism is valence-contingent. … Our data show that the restricted processing brought about by negative emotions is reflected in the intersubject similarity in time courses of brain activity: The more negative emotions individuals feel, the more similar is their brain activation in the emotion circuit as well as in the default-mode network, whereas when the subjects experience positive emotions promoting free exploration, their brains process the sensory input more individually, resulting in lower ISC (intersubject correlation).


My problem is that the word ‘synchronization’ is somewhat misleading in this paper. I understand synchronization to be the phase locking of two oscillations or the instantaneous matching of two events. I could accept that there is synchrony between two brains but this paper did not measure it. There was no precise timing of events found here. They show subjects are reacting in similar ways but not in synchrony – the precision of timing is just not there; the study protocol cannot show synchrony.


The subjects viewed film clips with the dialog removed while undergoing a fRMI scan. They viewed the clips a second time and produced a record of their emotional responses and the intensity of those responses. These were not simple amateur film clips; they were from When Harry Met Sally and The Godfather. In a previous posting in this blog (here) I commented in the power of well-made professional movies to control brain activity.


Here are their conclusions (just ignore the synchronization word):

Sharing other individuals’ emotional states enables predictions of their behavior, and shared affective, sensory, and attentional representations may provide the key to understanding other minds. We argue that emotions enhance intersubject synchronization of brain activity and thus tune-in specific brain networks across individuals to support similar perception, experiencing, and prediction of the world. Our findings suggest that such synchronization of emotions across individuals provides an attentional and affective framework for interpreting others’ actions. This hypothesis accords with the proposals that perceived emotional states in others are constantly mapped into corresponding somatic and sensory representations in the observers’ brain. Through this kind of mind-simulation, we may estimate others’ goals and needs more accurately and tune our own behavior accordingly, thus supporting social interaction and coherence. We propose that high arousal serves to direct individuals’ attention similarly to features of the environment, whereas negative valence synchronizes brain circuitries, supporting emotional sensations across individuals. Through these mechanisms emotions could promote social interaction by enhancing the synchrony between brain activity and behavior across different individuals.

Nummenmaa, L., Glerean, E., Viinikainen, M., Jaaskelainen, I., Hari, R., & Sams, M. (2012). Emotions promote social interaction by synchronizing brain activity across individuals Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1206095109

2 thoughts on “In Sync?

  1. Thanks for this comment. Even if it has brought a tremendous amount of interresting results, other semantic issues have been raised with the growing interrest of the Social Neuroscience community to the Hyperscanning methodology. Another example is the concept of “social interaction”, which normally refers to a bi-directional and spontaneous exchange.

    JK: Indeed! Thanks for pointing that out. Janet

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