Play is not frivolous: it enhances brain structure and function..."
"and promotes executive function (ie, the process of learning, rather than the content), which allow us to pursue goals and ignore distractions. Moreover, play supports the formation of the safe, stable, and nurturing relationships with all caregivers that children need for healthy development. Card games, board games, and outdoor play that promote social interaction and rule following are examples of healthy play."
Yogman, M., Garner, A.
Committee on Psychosocial Aspects of Child and Family Health, and the Committee on Early Childhood, Adoption, and Dependent Care
"The Power of Play: A Pediatric Role in Enhancing Development in Young Children"