Control variable strategies can go wrong and controls can make estimates worse rather than better. In this chapter, we discuss why control variables always deserve skepticism and require specific justification. We discuss criteria for plausible controls, bad controls, and why one should not control for everything we can measure (aka kitchen sink models). There are common conditions in which controlling for a variable causes bias, and therefore when excluding that control variable reduces bias.

Chapter 5 focuses on the psychology of the fair process effect. The chapter notes that although the effect is often there, it is important to study it in the context in which it is supposed to appear. After all, the relevance of various criteria and psychological processes may vary across different contexts and the different people present in those contexts. The chapter also notes that it is important to specify which types of dependent variables, such as trust or protest intentions, are most likely to be affected by the fair process effect under consideration. Relevant moderators (such as personal uncertainty) and mediators (such as perceived legitimacy) are discussed as well. The chapter ends with discussing the systemic aspects that are important when understanding the functioning of the fair process effect and how to prevent the effect from being misused in system-justifying ways.