Previous research by Tsai and Kaufman (2010a, 2010b) has suggested that computer-simulated virtual pet dogs can be used as a potential medium to enhance children's development of empathy and humane attitudes toward animals. To gain a deeper understanding of how and why interacting with a virtual pet dog might influence children's social and emotional development, this study gathered detailed data regarding the effects of play duration and types of play interaction on the enhancement of children's empathy and humane attitudes. Quantitative findings revealed that participants who spent more time playing with their virtual pet tended to have higher humane attitude scores. In addition, play interaction that involved competing with a virtual pet dog was associated with higher empathy and humane attitude scores, and the reported number of incidents of care provided was associated with higher humane attitude scores. Qualitative findings showed that the participants built an emotional bond with their virtual pet dogs and that many participants believed that the virtual dogs had their own interests and personalities. Many participants tended to base activities they would like to do with their virtual pet dogs on what they perceived to be the virtual pet dog's interests and needs.