Can the synchronization of two brains predict whether two people will cooperate or defect? EEG hyperscanning provides an answer.
Interbrain synchrony (IBS) refers to the temporal coordination of neural oscillations between two individuals engaged in social interaction. This research investigates whether IBS serves as a predictor of collaborative decision-making outcomes — specifically whether two people will cooperate or defect in a social dilemma.
The study uses a classic Prisoner's Dilemma game as its behavioral paradigm. Two participants (a dyad) make simultaneous decisions to either cooperate or defect, with payoffs dependent on both choices. This paradigm provides a clean, measurable proxy for real-world collaborative decision making.
Neural data is collected using EEG-based hyperscanning — simultaneous EEG recording from both participants during interaction. The Drift-Diffusion Model (DDM) is used to analyze the decision process itself, separating drift rate, threshold, and non-decision time components.
Higher interbrain synchrony in the delta and theta frequency bands is reliably associated with subsequent cooperative decisions.
Dyads with greater pre-existing social closeness show higher IBS throughout the decision process.
The Drift-Diffusion Model predicts mutual defection outcomes better than mutual cooperation outcomes.
IBS accumulates over the course of the game, with effects building across trials rather than resetting between decisions.
Prediction accuracy differs meaningfully between dyads, suggesting that IBS signatures are partially relationship-specific.
These findings connect to the broader Synaptosearch research agenda in two ways: