Bridge Assumptions and Situational Mechanisms

Each rational action theory – whether held either in its narrow/strong or in its broad/weak form – has to clarify how the opportunity structure of the social situation should be linked to actors' individual motives – however the latter are defined. To do so, bridge assumptions specifying to which extent material resources, power, norms, or rights of the social situation pre-structure individual action have to be constructed. However, in numerous empirical investigations bridge assumptions are completely missing or underspecified. One reason for this might be that hitherto, the question of how to construct bridge assumptions has not been answered very clearly. Although the necessity of bridge assumptions is demonstrated in every rational choice textbook, there has been surprisingly little attention to methodological aspects of their construction. An exception is the mid-90s debate on the question whether bridge assumptions should be formulated in a theory-rich way – i.e. by means of presupposing actors to strive for universal final aims such as social and physical wellbeing (Lindenberg 1996) – or on strictly empirical grounds (Opp 1996; Kelle/Lüdemann 1996). We consider this debate to be only the starting point on the way towards a methodology of constructing bridge assumptions.

In the present contribution, we first use evidence from published multilevel studies to establish the phenomenon (Merton 1987) of missing or underspecified bridge assumptions in contemporary quantitative sociological research. Second, we refer to the theory of social rationality (Lindenberg 2001, 2008) to suggest a strategy of how to formulate bridge assumptions in a theory-rich way. We intend to reconstruct both focal and background goals and how the latter might either foster or attenuate the relative salience of the former. Moreover, we demonstrate how the desires, beliefs, and opportunity (DBO) model (Hedström 2005) can be used to disentangle different forms of situational mechanisms.