Summary: A new study finds that when two people actively collaborate toward a shared goal, their brains begin to process information in increasingly similar ways. Using EEG hyperscanning, researchers observed that while all participants showed comparable early sensory responses to visual patterns, only real collaborating pairs developed sustained neural alignment tied to the specific rules they agreed to use.
This neural alignment grew stronger as pairs improved at their joint task, reflecting a shared cognitive strategy that emerged through cooperative practice. The findings demonstrate that collaboration reshapes neural processing and offer insight into how groups coordinate, make decisions, and develop shared practices.
Key facts:
- Neural alignment: Collaborating pairs showed converging brain-processing patterns after roughly 200 ms following a stimulus.
- Learning effect: The longer pairs worked together, the stronger their neural alignment became.
- Shared rules matter: Alignment beyond early sensory responses was observed only when partners used mutually agreed-upon strategies.
Source: PLOS Biology (published November 25th)
Overview
Humans depend on collaboration for tasks ranging from everyday chores to complex social endeavors. Effective cooperation requires that partners perceive the same features of the world and apply the same decision rules—agreeing, for example, which fruits are ripe and which to leave behind. This study, led by Denise Moerel and colleagues at Western Sydney University, investigated how shared task rules affect neural processing when two people work together.
The research team recruited 24 pairs of participants to perform a visual categorization task. Before starting, each pair agreed on a rule to categorize shapes and patterns—options included sorting by line orientation, thickness, contrast, or overall shape. Participants then completed the task while seated back-to-back so they could not see each other, and researchers recorded simultaneous electroencephalography (EEG) from both partners to examine how their brain activity aligned over time.
During the first 45–180 milliseconds after a stimulus appeared, all participants showed similar neural responses. These rapid responses reflect basic sensory processing of the visual pattern. Crucially, after roughly 200 milliseconds, activity began to align only within genuine collaborating pairs and not in randomly paired controls. This later alignment corresponded to the partners’ shared application of the categorization rule and became stronger as pairs practiced and improved.
The results indicate two distinct phases of interbrain similarity: an early, stimulus-driven alignment that occurs across individuals exposed to the same input, and a later, collaboration-specific alignment that reflects shared cognitive and decision-making processes. The latter depends on partners forming and using common rules and appears to strengthen with joint experience.
Implications
These findings suggest that successful cooperation involves not only coordinating behavior but also aligning internal representations of information. When people learn to apply the same rules, their neural activity begins to represent task-relevant information in a similar way, which may facilitate smoother coordination, more efficient joint decisions, and the emergence of shared practices or traditions within groups.
Funding: This work was supported by the Australian Research Council through a Discovery Project (DP220103047) and a Discovery Early Career Researcher Award (DE230100380). The named investigators received salary support from these awards. The funders did not influence study design, data collection and analysis, publication decisions, or manuscript preparation.
Key questions answered
A: How pairs of people process information when collaborating on a shared categorization task.
A: Simultaneous EEG (hyperscanning) recorded neural responses while partners worked back-to-back on the same task.
A: Brain activity became more similar only in pairs actively cooperating, and this alignment strengthened with practice and with shared application of agreed rules.
Editorial notes
- This article was edited by a Neuroscience News editor.
- The original journal paper was reviewed in full.
- Additional context and clarification were added by editorial staff to aid reader understanding.
About this neuroscience research news
Author: Claire Turner
Source: PLOS Biology
Contact: Claire Turner – PLOS
Image: The image is credited to Neuroscience News
Original research: Open access. “Collaborative rule learning promotes interbrain information alignment” by Denise Moerel et al., published in PLOS Biology.
Abstract
Collaborative rule learning promotes interbrain information alignment
Social interaction shapes how we perceive and interpret incoming information. Alignment between the sensory and cognitive processes of interacting individuals supports successful cooperation and communication, but the neural basis of this alignment has been unclear. This study applied Representational Similarity Analysis (RSA) to EEG hyperscanning data from 24 pairs performing a rule-based categorization task together.
Interbrain information alignment emerged within 45 ms of stimulus presentation and persisted for hundreds of milliseconds. Early alignment (45–180 ms) appeared in both real pairs and randomly matched pseudo-pairs, reflecting shared sensory responses to the same visual input. Importantly, alignment after 200 ms was unique to real collaborating pairs, increased with practice, and was driven by shared representations related to the categorization rules the pairs had formed. These findings reveal distinct neural processes underlying interbrain information alignment during social interaction and demonstrate how Interbrain RSA can disentangle sensory and collaboration-specific components of shared processing.