Strangers Sync Better: New Insights in Brain Synchronization

Summary: Individuals with weak social ties exhibit more synchronized brain activity during cooperative tasks than those with strong ties. Researchers challenged the traditional view that stronger social connections lead to greater neural coordination.

Using EEG, they measured brain activity in 14 pairs of strangers and 13 pairs of acquaintances engaged in a joint tapping task. Their findings suggest that the unfamiliarity between strangers necessitates greater neural effort, enhancing synchronization.

Key Facts:

  1. The study found greater intra-brain synchronization among strangers than acquaintances, particularly in the theta frequency band.
  2. Enhanced synchronization in strangers was evident through denser neural networks, indicating a more connected EEG activity.
  3. This research contradicts previous assumptions that stronger social bonds always correlate with higher levels of brain synchronization.

Source: Waseda University

We experience the world and connect with others through social interactions. Engaging in activities, such as conversations, cooperative tasks, and intimate relationships, deeply affect brain activity leading to coordinated neural activity within an individual’s brain (intra-brain synchronization) and between the brains of multiple individuals (inter-brain synchronization).

Researchers study brain synchronizations to understand the neural processes behind social behaviors. This knowledge can help diagnose and treat conditions like social anxiety and communication-related disorders.

This shows the outline of two heads.
Furthermore, binary undirected graphs constructed to represent the connectivity between EEG channels showed that the neural network was more densely connected in strangers than in acquaintances. Credit: Neuroscience News

However, investigations on brain synchronization have primarily focused on groups with strong social ties, such as romantic couples and parents and children.

In a study published in Scientific Reports on February 29, 2024, researchers from Waseda University in Japan reveal that cooperative interactive tasks between individuals with weak social ties result in more synchronized brain activity compared to individuals with strong ties.

“Our findings challenge the conventional understanding that stronger social ties predict greater brain synchronization and offer fresh insights into neural networking during social interactions,” says lead researcher Dr. Yuto Kurihara, Research Associate at the Faculty of Human Sciences at Waseda University.

The research team also included Dr. Toru Takahashi from the Advanced Research Center for Human Sciences and Professor Rieko Osu from the Faculty of Human Sciences at Waseda University.

They studied 14 pairs of strangers who met for the first time and 13 acquaintance pairs, in which one participant brought their partner. Due to artifacts, 21 pairs were included in the analysis (stranger pairs: 11, acquaintance pairs: 10).

The participants were given a joint tapping task, where they had to tap a mouse button in opposite rhythms. Each participant wore earphones to hear both their taps and their partner’s taps, and they had to anticipate their partner’s movements.

Brain activity was captured using electroencephalograph (EEG) electrodes placed on their scalp for four tapping conditions: slow tapping with a 0.5-second interval, fast tapping with a 0.25-second interval, tapping freely at their preferred frequency, and tapping coordinated with a metronome at 0.50-second intervals (a pseudo condition).

The study investigated how brain signals synchronize across the theta (4–7 Hz), alpha (8–12 Hz), and beta (13–30 Hz) frequency bands.

EEG analysis revealed that pairs of strangers exhibited greater intra-brain synchronization in the theta band, compared to acquainted pairs.

Furthermore, binary undirected graphs constructed to represent the connectivity between EEG channels showed that the neural network was more densely connected in strangers than in acquaintances.

“Surprisingly, despite having weaker social ties, stranger pairs demonstrated more robust intra- and inter-brain EEG networks than acquainted pairs,” comments Dr. Kurihara.

Researchers suggest that the lack of familiarity between strangers requires a more involved process for predicting each other’s actions or behaviors in a cooperative task. Consequently, this heightened engagement leads to a more efficient transfer of information between closely connected nodes within the neural network.

This finding underscores the importance of weak social ties in shaping social relationships and individual behavior.

“By demonstrating that strangers exhibit heightened intra- and inter-brain synchronization, our research highlights the potential of weak ties in fostering new connections and understanding the neural underpinnings of social interactions,” says Dr. Kurihara.

About this brain synchronization and social neuroscience research news

Author: Armand Aponte
Source: Waseda University
Contact: Armand Aponte – Waseda University
Image: The image is credited to Neuroscience News

Original Research: Open access.
The topology of interpersonal neural network in weak social ties” by Yuto Kurihara et al. Scientific Reports


The topology of interpersonal neural network in weak social ties

The strategies for social interaction between strangers differ from those between acquaintances, whereas the differences in neural basis of social interaction have not been fully elucidated.

In this study, we examined the geometrical properties of interpersonal neural networks in pairs of strangers and acquaintances during antiphase joint tapping.

Dual electroencephalogram (EEG) of 29 channels per participant was measured from 14 strangers and 13 acquaintance pairs.Intra-brain synchronizations were calculated using the weighted phase lag index (wPLI) for intra-brain electrode combinations, and inter-brain synchronizations were calculated using the phase locking value (PLV) for inter-brain electrode combinations in the theta, alpha, and beta frequency bands.

For each participant pair, electrode combinations with larger wPLI/PLV than their surrogates were defined as the edges of the neural networks.

We calculated global efficiency, local efficiency, and modularity derived from graph theory for the combined intra- and inter-brain networks of each pair.

In the theta band networks, stranger pairs showed larger local efficiency than acquaintance pairs, indicating that the two brains of stranger pairs were more densely connected.

Hence, weak social ties require extensive social interactions and result in high efficiency of information transfer between neighbors in neural network.

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