Unlocking Personality: How Situational Strength and Situational Affordances Shape Behavioral Expression

For over a century, psychologists have debated whether personality traits or situational factors exert greater influence on human behavior. Building on the interactionist legacy of Lewin’s (1936) equation B = f(P, S), contemporary consensus holds that behavior emerges from the interplay between person and situation. Yet, despite this consensus, limited progress has been made in delineating how traits and situational features jointly shape both the level and variability of behavior. This dissertation advances a situational perspective in personality psychology by integrating two influential frameworks: the situational strength framework (Mischel, 1977) and trait activation theory (Tett & Guterman, 2000). Across four empirical chapters, it investigates how situational strength—the degree to which situations constrain behavior through clarity, consequences, and constraints—and situational affordances—opportunities for trait expression—jointly regulate behavioral expression. Chapter 2 introduces the Generic Situational Strength (GSS) scale, a validated measure applicable across diverse contexts. Chapter 3 meta-analyzes variance in cooperation in economic games, providing systematic evidence for the restricted variance hypothesis central to the situational strength framework: strong situations, characterized by higher consequences, constraints, and clarity, reduce variability in behavior. Chapter 4 extends trait activation theory to unstructured, real-life contexts using a retrospective diary study, examining how HEXACO traits are expressed across daily situations. Chapter 5 focuses on incentivized dishonesty, revealing that strong situations do not always restrict variance; when paired with high situational affordances, they may instead amplify individual differences in behavior. Together, these studies offer a nuanced account of how situational features shape not only mean behavioral tendencies but also their variability. Chapter 6 discusses theoretical and methodological implications, including disentangling the interplay between strength and affordances, refining affordance frameworks, examining the neutralizing role of strength, and adopting ecologically valid, multi-method designs to study behavior in context. This work deepens our understanding of personality expression in both controlled and naturalistic settings, and invites further exploration of the complex entanglement between traits and situations.