Jan's research studies intergroup and interpersonal relationships with two guiding research questions. First, what causes people's willingness to harm others and defend inequalities? For example, Jan's research has found that categorizing others into ingroups and outgroups is so powerful that it even shapes the application of moral principles that are thought to be universal. Another example is that Jan's research has found that people from disadvantaged groups have limited access to political leadership positions not only due to prejudice but also due to concerns about the perceived electability of these candidates.
Second, how can personal or societal change be achieved that increases equality and/or reduces harm? Jan has developed interventions that increase support for policies that aim to reduce economic inequality or increase opportunity for immigrants. Jan has also led the Strengthening Democracy Challenge, a mega-study that tested 25 crowdsourced interventions for reducing anti-democratic attitudes and partisan animosity.
Jan is also interested in meta-scientific questions about how to make scientific progress more reliable. He has written on how to use Open Science principles in the social sciences and contributed to JASP, a free and open-source statistics software.