Americans donate over 300 billion dollars a year to charity, but the psychological factors that govern whether to give, and how much to give, are still not well understood. Our understanding of charitable giving is based primarily upon the intuitions of fundraisers or correlational data which cannot establish causal relationships. By contrast, the chapters in this book study charity using experimental methods in which the variables of interest are experimentally manipulated. As a result, it becomes possible to identify the causal factors that underlie giving, and to design effective intervention programs that can help increase the likelihood and amount that people contribute to a cause.