Ivana Konvalinka

Follow you, follow me: Continuous mutual prediction and adaptation in joint tapping

To study the mechanisms of coordination that are fundamental to successful interactions we carried out a joint finger tapping experiment in which pairs of participants were asked to maintain a given beat while synchronizing to an auditory signal coming from the other person or the computer. When both were hearing each other, the pair became a coupled, mutually and continuously adaptive unit of two “hyper-followers”, with their intertap intervals (ITIs) oscillating in opposite directions on a tap-to-tap basis. There was thus no evidence for the emergence of a leader–follower strategy. We also found that dyads were equally good at synchronizing with the irregular, but responsive other as with the predictable, unresponsive computer. However, they performed worse when the “other” was both irregular and unresponsive. We thus propose that interpersonal coordination is facilitated by the mutual abilities to (a) predict the others subsequent action and (b) adapt accordingly on a millisecond timescale.

The two-brain approach: how can mutually interacting brains teach us something about social interaction?

Measuring brain activity simultaneously from two people interacting is intuitively appealing if one is interested in putative neural markers of social interaction. However, given the complex nature of interactions, it has proven difficult to carry out two-person brain imaging experiments in a methodologically feasible and conceptually relevant way. Only a small number of recent studies have put this into practice, using fMRI, EEG, or NIRS. Here, we review two main two-brain methodological approaches, each with two conceptual strategies. The first group has employed two-brain fMRI recordings, studying (1) turn-based interactions on the order of seconds, or (2) pseudo-interactive scenarios, where only one person is scanned at a time, investigating the flow of information between brains. The second group of studies has recorded dual EEG/NIRS from two people interacting, in (1) face-to-face turn-based interactions, investigating functional connectivity between theory-of-mind regions of interacting partners, or in (2) continuous mutual interactions on millisecond timescales, to measure coupling between the activity in one persons brain and the activity in the others brain. We discuss the questions these approaches have addressed, and consider scenarios when simultaneous two-brain recordings are needed. Furthermore, we suggest that (1) quantification of inter-personal neural effects via measures of emergence, and (2) multivariate decoding models that generalize source-specific features of interaction, may provide novel tools to study brains in interaction. This may allow for a better understanding of social cognition as both representation and participation.

Frontal alpha oscillations distinguish leaders from followers: Multivariate decoding of mutually interacting brains

Successful social interactions rely upon the abilities of two or more people to mutually exchange information in real-time, while simultaneously adapting to one another. The neural basis of social cognition has mostly been investigated in isolated individuals, and more recently using two-person paradigms to quantify the neuronal dynamics underlying social interaction. While several studies have shown the relevance of understanding complementary and mutually adaptive processes, the neural mechanisms underlying such coordinative behavioral patterns during joint action remain largely unknown. Here, we employed a synchronized finger-tapping task while measuring dual-EEG from pairs of human participants who either mutually adjusted to each other in an interactive task or followed a computer metronome. Neurophysiologically, the interactive condition was characterized by a stronger suppression of alpha and low-beta oscillations over motor and frontal areas in contrast to the non-interactive computer condition. A multivariate analysis of two-brain activity to classify interactive versus non-interactive trials revealed asymmetric patterns of the frontal alpha-suppression in each pair, during both task anticipation and execution, such that only one member showed the frontal component. Analysis of the behavioral data showed that this distinction coincided with the leader-follower relationship in 8/9 pairs, with the leaders characterized by the stronger frontal alpha-suppression. This suggests that leaders invest more resources in prospective planning and control. Hence our results show that the spontaneous emergence of leader-follower relationships in dyadic interactions can be predicted from EEG recordings of brain activity prior to and during interaction. Furthermore, this emphasizes the importance of investigating complementarity in joint action.

Analyzing Social Interactions: The Promises and Challenges of Using Cross Recurrence Quantification Analysis

The scientific investigation of social interactions presents substantial challenges: interacting agents engage each other at many different levels and timescales (motor and physiological coordination, joint attention, linguistic exchanges, etc.), often making their behaviors interdependent in non-linear ways. In this paper we review the current use of Cross Recurrence Quantification Analysis (CRQA) in the analysis of social interactions, and assess its potential and challenges. We argue that the method can sensitively grasp the dynamics of human interactions, and that it has started producing valuable knowledge about them. However, much work is still necessary: more systematic analyses and interpretation of the recurrence indexes and more consistent reporting of the results,more emphasis on theory-driven studies, exploring interactions involving more than 2 agents and multiple aspects of coordination,and assessing and quantifying complementary coordinative mechanisms. These challenges are discussed and operationalized in recommendations to further develop the field.

Quantifying collective effervescence: Heart-rate dynamics at a fire-walking ritual.

Collective rituals are ubiquitous and resilient features of all known human cultures. They are also functionally opaque, costly, and sometimes dangerous. Social scientists have speculated that collective rituals generate benefits in excess of their costs by reinforcing social bonding and group solidarity, yet quantitative evidence for these conjectures is scarce. Our recent study measured the physiological effects of a highly arousing Spanish fire-walking ritual, revealing shared patterns in heart-rate dynamics between participants and related spectators. We briefly describe our results, and consider their implications.

Autobiographical Memory in a Fire-Walking Ritual

Anthropological theories have discussed the efffects of participation in high-arousal rituals in the formation of autobiographical memory; however, precise measurements for such efffects are lacking. In this study, we examined episodic recall among participants in a highly arousing firewalking ritual. To assess arousal, we used heart rate measurements. To assess the dynamics of episodic memories, we obtained reports immediately after the event and two months later. We evaluated memory accuracy from video footage. Immediately after the event, participants’ reports revealed limited recall, low confijidence and high accuracy. Two months later we found more inaccurate memories and higher confijidence. Whereas cognitive theories of ritual have predicted flashbulb memories for highly arousing rituals, we found that memories were strongly suppressed immediately after the event and only later evolved confijidence and detail. Physiological measurements revealed a spectacular discrepancy between actual heart rates and self-reported arousal. This dissociation between subjective reports and objective measurements of arousal is consistent with a cognitive resource depletion model. We argue that expressive suppression may provide a link between individual memories and cultural understandings of high-arousal rituals.

Synchronised and complementary coordination mechanisms in an asymmetric joint aiming task

Many forms of social interaction require that behaviour be coordinated in the here and now. Much research has been conducted on how people coordinate their actions in real time to achieve a joint goal, showing that people use both synchronised (i.e. symmetric) and complementary (i.e. asymmetric) strategies. These two mechanisms have been mostly studied independently, the former in the context of rhythmic tasks, and the latter in non-rhythmic tasks. However, people often balance these two strategies in real-life social interactions, in order to achieve a joint goal more effectively. Here, our aim was to investigate how people may implicitly balance synchronisation and complementarity in a continuous joint aiming task. We asked dyads to synchronise the timing of their clicks between targets, while changing task constraints for one member of the dyad (i.e. different task difficulties) to asymmetrically perturb the continuous interaction. This allowed us to investigate how individuals implicitly negotiate complementary leader–follower dynamics to achieve synchronisation. We found that dyads flexibly switch from mutual to asymmetric adaptation given variations in task constraints. Specifically, our results show that both members adapt equally up to a certain level of difficulty; after this point, the partner with the difficult task becomes less adaptive, and hence more of a leader, while the adaptability of the member with the easier task remains unchanged. This proves to be an effective strategy in this asymmetric task, as people synchronise better with an irregular, but adaptive partner, than with a completely predictable, but non-responsive metronome. These results show that given asymmetric task constraints, adaptability, rather than predictability, facilitates coordination.

The Fire-Walker’s High: Affect and Physiological Responses in an Extreme Collective Ritual

How do people feel during extreme collective rituals? Despite longstanding speculation, few studies have attempted to quantify ritual experiences. Using a novel pre/post design, we quantified physiological fluctuations (heart rates) and self-reported affective states from a collective fire-walking ritual in a Mauritian Hindu community. Specifically, we compared changes in levels of happiness, fatigue, and heart rate reactivity among high-ordeal participants (fire-walkers), low-ordeal participants (non-fire-walking participants with familial bonds to fire-walkers) and spectators (unrelated/unknown to the fire-walkers). We observed that fire-walkers experienced the highest increase in heart rate and reported greater happiness post-ritual compared to low-ordeal participants and spectators. Low-ordeal participants reported increased fatigue after the ritual compared to both fire-walkers and spectators, suggesting empathetic identification effects. Thus, witnessing the ritualistic suffering of loved ones may be more exhausting than experiencing suffering oneself. The findings demonstrate that the level of ritual involvement is important for shaping affective responses to collective rituals. Enduring a ritual ordeal is associated with greater happiness, whereas observing a loved-one endure a ritual ordeal is associated with greater fatigue post-ritual.

Syncopation affects free body-movement in musical groove

One of the most immediate and overt ways in which people respond to music is by moving their bodies to the beat. However, the extent to which the rhythmic complexity of groove—specifically its syncopation—contributes to how people spontaneously move to music is largely unexplored. Here, we measured free movements in hand and torso while participants listened to drum-breaks with various degrees of syncopation. We found that drum-breaks with medium degrees of syncopation were associated with the same amount of acceleration and synchronisation as low degrees of syncopation. Participants who enjoyed dancing made more complex movements than those who did not enjoy dancing. While for all participants hand movements accelerated more and were more complex, torso movements were more synchronised to the beat. Overall, movements were mostly synchronised to the main beat and half-beat level, depending on the body-part. We demonstrate that while people do not move or synchronise much to rhythms with high syncopation when dancing spontaneously to music, the relationship between rhythmic complexity and synchronisation is less linear than in simple finger-tapping studies.

Images from a jointly-arousing collective ritual reveal affective polarization

Collective rituals are biologically ancient and culturally pervasive, yet few studies have quantified their effects on participants. We assessed two plausible models from qualitative anthropology: ritual empathy predicts affective convergence among all ritual participants irrespective of ritual role; rite-of-passage predicts emotional differences, specifically that ritual initiates will express relatively negative valence when compared with non-initiates. To evaluate model predictions, images of participants in a Spanish fire-walking ritual were extracted from video footage and assessed by nine Spanish raters for arousal and valence. Consistent with rite-of-passage predictions, we found that arousal jointly increased for all participants but that valence differed by ritual role: fire-walkers exhibited increasingly positive arousal and increasingly negative valence when compared with passengers. This result offers the first quantified evidence for rite of passage dynamics within a highly arousing collective ritual. Methodologically, we show that surprisingly simple and non-invasive data structures (rated video images) may be combined with methods from evolutionary ecology (Bayesian Generalized Linear Mixed Effects models) to clarify poorly understood dimensions of the human condition.