This thesis contributes to the research on other regarding preferences by experimental studies. Chapter 1 investigates the feasibility of efficiency gains in a principal-agent relationship by voluntary leadership. Chapter 2 investigates whether negative reciprocity can be documented if the worse off proposer does not create – but even eliminates – inequality at the responder’s cost. Chapter 3 is a principal-agent game. It investigates the performance and self-selection of heterogeneous agents in a group or an individual task. Chapter 4 investigates how the method of role uncertainty biases other regarding preferences in experimental games.