Research synthesis techniques such as systematic reviews and metaanalyseshave become standard methods for aggregating the resultsfrom thematically related research in psychology. In this "Hotspots"issue, leading researchers describe state of the art systematic reviewsand meta-analyses on topics currently being debated in psychology,meta-analytic replications and extensions of previously publishedsynthesis, and methodological advances in research synthesismethods. Using the latest research synthesis techniques, leading researchersdescribe the state of the art in various research fields, testand compare theories, and derive conclusions about the effectivenessof interventions.