In this chapter, we explore an actor-centric approach that emphasizes strategic interaction and offers an alternative to IV-estimation to pursue the evaluation of Master Hypothesis 4. We proceed in two steps. First, we introduce a simple formal model that captures the most important strategic dimension and highlights what is crucial for reverse causation: The conditions under which governments are likely to share power depending on the level of threat posed by a domestic challenger. As we have shown in Chapters 3 and 6, previous research on the origins of power sharing highlights either government incentives for the co-optation of threatening challengers through power sharing arrangement or risk-diversion by means of exclusion so as to avoid perilous infighting. Rather than favoring either consideration at the expense of the other, the model presented here unifies these mechanisms and shows that both have their place - depending on the challenger's level of threat as well as the government's ability to provide credible guarantees. In a second step, the chapter provides a novel statistical estimator that closely mirrors the strategic logic of the theoretical model, but also accounts for the selection on unobservables. Applied to data at the level of ethnic groups around the globe since World War II, the model offers strong evidence that governments do indeed strategically use power sharing as a way of managing the risk of conflict. In short, power sharing is systematically endogenous to conflict as suggested by Master Hypothesis 4. Moreover, the results reaffirm that power sharing systematically causes peace, and that naïve analyses that do not account for endogeneity tend to underestimate this effect.

We start this conceptual and theoretical chapter by recapitulating previous work on exclusion and civil war by outlining how it connects political exclusion and grievances with the onset of conflict. Consequently, if power sharing reduces inequality and exclusion, peace becomes more likely through a grievance-reducing effect. In addition, power sharing can also bring peace through confidence building. After defining the key notion of power sharing practices, we introduce our first Master Hypothesis about linking both governmental and territorial power-sharing practices to the reduction of civil conflict. The rest of the chapter advances four additional master hypotheses that correspond to the four initial challenges confronting research on power sharing and conflict that were introduced in Chapter 1. First, we derive Master Hypothesis 2 by arguing that practices channel the main conflict-reducing effect of formal power-sharing institutions and also reduce conflict even in the absence of formal institutions. According to Master Hypothesis 3, power-sharing practices have a pacifying effect both before and after the first conflict but the risk of conflict onset is generally higher in the latter case. With Master Hypothesis 4, we address the important issue of endogeneity by showing that governments introduce power-sharing arrangements mostly as a way to co-opt potentially violent challenges to their sovereign power. Finally, under the heading of Master Hypothesis 5, we show how territorial power sharing, especially in relationships already characterized by past violence, may be insufficient to build confidence in support of stable peace. In such cases, autonomy and other territorial approaches are more effective if combined with central power-sharing practices.

Participation in activities that provide opportunities for mental, physical, or social engagement have been supported as cognitively protective in later life. Theories propose how mentally stimulating activities might improve or maintain specific cognitive abilities across the life course or reduce age-related cognitive changes, for example, while physical activities might promote brain health via a reduction in cardiovascular risk profiles. Given that such lifestyles and behaviors are potentially modifiable, positive associations between activity participation and maintained cognitive abilities in old age highlight leisure-time pursuits as targets for intervention. However, associations between activity participation and cognitive aging may be prone to reverse causation: those with higher engagement across the life course might have always had higher levels of cognitive ability. Life course approaches are therefore needed to correctly identify the potentially beneficial effects of activity participation. In addition, given the growth and development of cognitive abilities across the life span, there may be specific types of activity or engagement that are beneficial at different points. Understanding the associations between mental, physical, and social activity participation and cognitive aging supports the development of interventions against age-related cognitive decline, ranging from targeted cognitive training programs to broader engagement-based approaches. An ultimate goal of research exploring activity participation and cognitive aging is to provide clear and accurate information to individuals regarding the steps they might take to promote brain health in later life.