Economic value is a factor in comparing alternatives for the purpose of policymaking. As the economic value of non-market goods is unknown, economic valuation techniques are applied. This study provides an overview of existing studies that examine if the difference in the cause of environmental damages influences economic value. The modern economic theory stipulates that the result is not influenced by the difference in causes (e.g., natural or human) as long as the result is the same, while psychological evidence has provided the opposite results. Recent studies from both economics and psychology have considered differences in alternative causes, and two effects are proclaimed: outrage (Kahneman et al. 1993), which indicates that people find man-made cases more serious than natural cases, and moral responsibility (Walker et al. 1999), which implies the opposite. Subsequent studies have resolved these opposing claims by pointing out whether or not responsible subjects are specified. Relevant studies have accumulated, but further research is needed because many other factors may be related to the results. This study summarizes most of the related literature and suggests remaining issues for the sake of future analyses and real-life applications.