Who Gets Socialized? Liberalization or Negative Selection of Higher Education

Active political engagement and participation are widely recognized as essential to democratic citizenship, yet we hardly understand how different educational pathways produce differentiated forms of political citizenship. Recent findings have shown that we do not fully understand whether specific fields of study, rather than graduating with a tertiary degree generally, drive civic socialization. However, such heterogeneity matters greatly for understanding the political consequences of educational stratification and sorting. I address this gap by decomposing tertiary education effects by field of study, contrasting Humanities and Social Sciences (HSS) against STEM fields in Germany and the UK. This research design extends the Brand and Xie (2010) heterogeneous treatment effects framework to compare tracked (Germany) versus comprehensive (UK) educational systems. I analyse political engagement and behaviour using two sets of longitudinal panel data from Germany and the United Kingdom. Employing propensity score methods with rich pre-treatment covariates, including social origins, parental occupation, secondary school subject grades, and youth political engagement. The results reveal that the field of study matters more than tertiary attainment for political engagement. Both political outcomes demonstrate negative selection patterns; students who are unlikely to enrol in HSS fields change the most (becoming more engaged and voting more left-wing) upon graduation. This strongly suggests evidence of socialization. STEM fields show no such compensatory effects. Between the two countries, I find similar negative selection patterns for tertiary attainment and equalizing effects across parental education backgrounds. These findings reveal how educational systems create differentiated citizenship identities and practices, with liberal arts education serving a distinct civic function primarily for those otherwise excluded from politically engaged citizenship. Together, these findings highlight the importance of examining field of study differences and support socialization interpretations, with the caveat that this is only the case for those least likely to attain a liberal arts qualification in tertiary education. Field of study differences within tertiary education emerge as a crucial and understudied aspect of educational causes of political change.