State-of-the art research synthesis methods for psychologistsThis fourth "Hotspots in Psychology" is devoted to systematic reviews and meta-analyses in research-active fields that have generated a considerable number of primary studies. The common denominator is the research synthesis nature of the contributions, and not a specific psychological topic or theme that all articles have to address. This issue explores methodological advances in research synthesis methods relevant for any subfield of psychology. The contributions include: the application of a network meta-analytic approach to analyze the effect of transcranial direct current stimulation on memory; analyzing the performance of a meta-analytic structural equation modeling approach when variables in primary studies have been artificially dichotomized; assessing quality-related aspects of systematic reviews with AMSTAR and AMSTAR2; as well as a graphical approach to depict study-level statistical power in the context of meta-analysis.