Improvement in cognitive development was associated with surrounding greenness, particularly with greenness at schools

This study examined the relationship between surrounding greenness and cognitive development in primary-age children in Barcelona, Spain. While previous studies found that exposure to green space was associated with better physical and mental health, they did not specifically look at cognitive development.

For this study, cognitive development was assessed through a 12-month change in developmental trajectory of working memory and attention. Computerized cognitive tests were administered to over 2500 children (age 7 – 10) every 3 months over the 12-month period. The children participating in the study had been in the same school for more than six months before the study began. The normalized difference vegetation index (NDVI) was used to measure greenness surrounding the children's home, their commuting route between home and school, and greenness within and around the school boundaries.

An analysis of the data found that an improvement in cognitive development was associated with surrounding greenness, particularly with greenness at schools. This association applied to (1) working memory (the system that holds multiple pieces of transitory information in the mind where they can be manipulated), (2) superior working memory (memory that involves continuous updating of the working memory buffer), and (3) decreased inattentiveness. These associations were only partly mediated by reductions in air pollution, suggesting that other mechanisms were likely supporting the associations.

The results of this study are consistent with previous research findings where residential greenness was related to better mental health, and higher school greenness was associated with better student performance. These findings also have important implications for policymakers in making evidence-based decisions. As this study suggests, there are feasible and achievable targeted interventions -- such as improving greenness at schools – that can contribute to improved cognitive development in children. These improvements, in turn, can lead to increased mental capital at the population level.