From the website
"Psychologists Jessica Dillon and Sandra Russ expected the opposite outcome when they analyzed 14 play studies that Russ conducted between 1985 and 2008. But as they report in “Changes in Children’s Play Over Two Decades,” an article in the Creativity Research Journal,the data told a story contrary to common assumptions. First, children’s use of imagination in play and their overall comfort and engagement with play activities actually increased over time. In addition, the results suggested that children today expressed less negative feelings in play. Finally, their capacity to express a wide range of positive emotions, to tell stories and to organize thoughts stayed consistent."