According to a recent study by casual game developer PopCap, nearly a quarter of internet users play games on social networks -- but the age of those players can differ significantly across regions.In its "2010 PopCap Social Gaming Research" report, the company found that fully two-thirds of social game players in the United States are 40 years of age or older, while the majority of players in the United Kingdom are under the age of 40.The ages of 30 to 49 seems to roughly be the transatlantic casual gaming sweet spot. Both nations have at least 40 percent of their social gamers in those ages. And below 30, social game activity in the U.S. tapers off significantly, while the same is true in the U.K. for ages above 49.Meanwhile, twice as many U.K. twenty-somethings (22 percent of those 22 to 29 years of age) play social games as in the U.S.Young adults and teens in both countries are the least interested in playing games on sites like Facebook and MySpace: only 9 percent of U.K. casual gamers are 21 years of age or younger, and the proportion is only 4 percent in the States.The statistics may reflect generational differences in the adoption of certain new communication trends in the two countries. It is possible older internet users in the U.K. have been less receptive to social networking and social gaming -- or that the younger generation in that country has simply picked it up even faster than in the United States.Some demographics are less variable. The gender breakdown in both countries reflects a somewhat higher proportion of female users, with that imbalance slightly higher in the U.K.: 58 percent of U.K. social gamers are female, versus 54 percent in the U.S.