Collaborative drawing offers new insights into how strangers become friends

Over a six-week period, 61 pairs of individuals met to engage in collaborative drawing, revealing new insights into how relationships form and brain activity changes during social interactions. The participants were divided into two age groups: 18-35 years and 70-85 years, with 31 cross-generational pairs and 30 pairs of the same age.

At the start, the participants did not know each other and had to become familiar with one another during the sessions. Each session involved drawing individually and together, with participants allowed to converse but instructed to remain silent while drawing. Wearable brain sensors recorded the participants' brain activity, allowing the researchers to investigate the relationship between brain synchrony and the development of social connections.

The study's primary focus was inter-brain synchrony, which occurs when two people perform a shared task and their brains react continuously to each other's actions. Previous research suggested that as people become familiar with one another, their brain activity patterns become increasingly similar. However, the researchers from ETH Zurich were surprised to find that, despite participants feeling closer over time, their brain activity patterns did not become more similar in cross-generational pairs.

In fact, the brain synchrony decreased in these pairs over the six weeks, while it increased in same-age pairs.

The researchers propose that this difference may be due to mutual prediction, a process in which people learn to anticipate and adapt to their counterpart's behavior. In the case of cross-generational pairs, the participants had to work harder to understand each other's perspectives, leading to a decline in brain synchrony. Meanwhile, same-age pairs, who already shared common experiences and interests, experienced increasing brain synchrony as they grew closer.