Explaining social inequalities in higher education (HE) participation is a highly relevant and popular research topic. In Germany, despite increasing participation in HE, the share of HE students from educationally advantaged parental homes has remained at a consistently high level since 2006 (Middendorff et al., 2017). Several studies show that these origin-specific inequalities in access to HE are largely due to students' educational decision-making (e.g. Daniel & Watermann, 2018; Becker & Hecken, 2007). The secondary effects of social origin according to Raymond Boudon (1974) make the largest explanatory contribution in these rational choice models, which include the social class differences in the valuation of study costs, study benefits and the probability of success in completing a degree (Schindler & Reimer, 2010). Components of social capital and cultural capital are often added as an auxiliary concept to factor analyses of educational decisions (e.g. Spangenberg et al., 2017; Lörz, 2012). Their direct effect on the intention to enrol in HE has not yet been sufficiently researched. This state of research is just one example of an international trend in quantitative education research that has emerged in recent years. Rational choice approaches are usually used to explain differences in social origin, supplemented by peripheral aspects of Pierre Bourdieu's (1986, 1977) theory of social reproduction (Hopf, 2014). In this way, Bourdieu's general concept is truncated and distorted when translated into empirical constructs (Lareau & Weininger, 2003; Sullivan, 2002). Apart from the continuing difficulty of translating Bourdieu's theoretical concepts into empirical evidence (Sullivan, 2001), there is no clear rationale for this preference for the rational choice paradigm. Both research paradigms have certain advantages and disadvantages (Vester, 2006) and it is first necessary to determine which one is appropriate for which research question. A comparative study of educational inequalities using both research traditions is still a research gap, which is why the topic is scientifically essential. The study presented in this article is based on the first wave of the 2015 "Studienberechtigtenpanel", a German panel study of school leavers with HE entrance qualifications. Linear regression analyses (N=25,195) were used to compare the theoretical assumptions of Boudon's rational educational choice with those of Bourdieu's theory of social space and capital. They confirm that both concepts, rational choice and social reproduction, cause social differences in study intention and can explain part of its variance. Overall, rational choice items have a higher explanatory contribution than social reproduction items, so that more than half of the effect of social origin on study intention can be explained by rational choice. Book-reading activity seems to be a suitable indicator of incorporated cultural capital, as it explains 5% of the variance in study intention. However, for an adequate measurement of the possession of cultural and social capital, it seems essential to complement the operationalisation with other factors. The findings suggest that rational choice constructs are products of complex socio-cultural processes that remain a black box in the study of educational inequalities. Future studies should work towards disentangling the primary and secondary effects of social origin by incorporating further aspects of socio-cultural process characteristics into models of rational educational choice. An adequate measurement of the mechanisms underlying educational inequalities allows for a more robust explanation and thus more precise policy implications for reducing social inequalities in access to HE.

The analysis is based on the first wave of the 2015 "Studienberechtigtenpanel, a German panel study of school leavers with HE entrance qualifications. Conducted by the German Centre for Higher Education Research and Science Studies (DZHW) since 1976, the "Studienberechtigtenpanel" focuses on the study intention as well as the educational decisions and trajectories of school leavers (Daniel et al., 2017). The 2015 graduation cohort was surveyed about six months before graduation. The net sample of the first wave consists of the data of 29,905 school leavers with Abitur (German HE entrance qualification) from the school year 2014/2015 (Schneider & Vietgen, 2021). Regression analysis was carried out to compare the theoretical assumptions of rational educational choices according to Raymond Boudon with those of Pierre Bourdieu's theory of social space and capital. In seven linear regression models (N=25,195), I estimated the influence of social origin as independent variable on the intention to study in HE as dependent variable. In subsequent model steps, components of the rational choice paradigm, including educational returns, costs of study, probability of success, and grade point average, as well as components of the theory of social reproduction, including cultural and social capital, were gradually added as third variables. This makes it possible to observe both the individual and the interplay between the two theoretical approaches in explaining social differences in study intention and in explaining study intention itself. Social origin has been operationalised as parental education on a maximum scale of the highest educational attainment of the mother and father. If at least one parent has an HE degree, parental education is considered academic, otherwise non-academic. Cultural capital was operationalised by the frequency with which respondents read books, and social capital by the frequency with which respondents were active in clubs. Intention to study in HE, estimated educational returns, costs, and the likelihood of successfully completing HE could be measured directly using Likert scales.

Hypothesis testing confirms that both concepts, rational choice and social reproduction, cause social differences in study intention and can explain part of its variance. Overall, the rational choice items have a higher explanatory contribution than the social reproduction items, so that more than half of the effect of social origin on study intention can be explained by rational choice. Almost one third of the differences in study intention are explained by the constructs of both theories. The results suggest that students from high educational backgrounds are more likely to enter the HE system because they differ from students from low educational backgrounds in their perceptions of the costs, benefits and chances of success of studying, in their school performance, and in their endowment of cultural capital. There is no evidence of a positive relationship between the possession of social capital and the intention to enrol in HE. Nevertheless, the cultural capital model explains 5% of the variance in the intention to study among German school leavers with an HE entrance certificate. In this respect, book-reading activity appears to be a suitable indicator of incorporated cultural capital. For an adequate measurement of the possession of cultural and social capital, however, it seems indispensable to supplement the operationalisation with further factors. In addition, a greater cultural distance from the field of HE seems to lead to a lower assessment of the probability of success in obtaining an HE degree. Thus, rational choice constructs are products of complex socio-cultural processes that have been internalised by individuals over a long period and remain a black box in the study of educational inequalities. Future studies should work towards unravelling the primary and secondary effects of social origin by incorporating further aspects of unconscious shaping and socio-cultural process characteristics into models of rational educational choice.

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