A new study published in Frontiers in Psychology found no association between playing violent video games (such as Call of Duty) and a reduction in empathy or desensitization to real acts of violence:
http://secondnexus.com/technology-and-innovation/violent-video-games/?utm_content=inf_10_1164_2&tse_id=INF_c819e6f02c8611e7ab1b4bd69f1788b7
