Green urban environments enhance brain-to-brain synchrony.

Previous studies have demonstrated that people focus on fewer specific features of natural environments compared to built environments. This may imply that neural activity stronger converge across individuals in green environments than in built environments, where people may focus very differently on diverse and often overloading urban stimulation. We hypothesized that the similarity of mental states across individuals should increase during exposure to green environments compared to built environments. Thus, we conducted an electroencephalography study in which we measured the correlation of neural responses among 30 participants using the inter-subject correlation (ISC). Using the ISC method, we calculated the similarity of the brain activity of a group of people as they were exposed to videos of 5-minute walks through parks, boulevards, or busy roads. The behavioral results showed that on average, participants rated the videos of parks as 39 and 65% more relaxing than boulevards and busy roads, correspondingly. Our electrophysiological results showed that the average similarity in brain activity, as measured by ISCs, was significantly stronger during the observation of parks compared to boulevards and busy roads. On average, ISCs for parks were 26 and 40% higher compared to boulevards and busy roads, respectively. We also found that parks increase the similarity of brain activity, particularly in the delta band, which reflects the most evolutionary old and phylogenetically preserved cortical activity. Our results further confirm that during urban walks in busy boulevards and highways, people's attention is distracted, as indicated by weaker brain synchronization between individuals.