This article describes how laboratory experiments are used by social psychologists and those in related fields to study conflict, negotiation, and mediation. In a laboratory experiment, the researcher experimentally controls one or more variables in controlled, artificial settings that induce processes likely to occur naturally. Laboratory experiments are the primary method used to establish cause-and-effect relationships among variables and to reduce alternative explanations; thus they are primarily concerned with validity of explanation. In this article, we describe several basic design features including conceptual replication, precise manipulation, and the use of a moderator variable, which all help assess the processes underlying a research finding. These design features foster conceptual internal validity, which describes the impact of one variable on another and the quality of such an explanation. Conceptual internal validity provides a basis for generalization of findings and thus new research. It also fosters strong inference, which helps build cumulative knowledge. Laboratory experiments are not well suited to answer all questions and problems – for example, they may not produce deep understanding of a particular historical event and must be supplemented by other methods, such as surveys and case studies.