Complex engineering systems such as bridges, roads, flood defence structures, and power pylons play an important role in our society. Unfortunately such systems are subject to deterioration, meaning that in course of time their condition falls from higher to lower, and possibly even to unacceptable, levels. Maintenance actions such as inspection, local repair and replacement should be done to retain such systems in or restore them to acceptable operating conditions. After all, the economic consequences of malfunctioning infrastructure systems can be huge. In the life-cycle management of engineering systems, the decisions regarding the timing and the type of maintenance depend on the temporal uncertainty associated with the deterioration. Hence it is of importance to model this uncertainty. In the literature, deterioration models based on Brownian motion and gamma process have had much attention, but a thorough comparison of these models lacks. In this thesis both models are compared on several aspects, both in a theoretical as well as in an empirical setting. Moreover, they are compared with physical process models, which can capture structural insights into the underlying process. For the latter a new framework is developed to draw inference. Next, models for imperfect maintenance are investigated. Finally, a review is given for systems consisting of multiple components.

The main focus of this thesis is to combine the multiple findings from social psychology and apply them with an economic approach to decision making. To this purpose, we investigate accountability and its interaction with market mechanisms, more specifically real incentives in experimental settings. This PhD thesis is structured as follows. Chapter 2 studies the effect of accountability on ambiguity aversion-the preference for known over normatively equivalent unknown probabilities. Chapter 3 follows up on the ambiguity aversion issue by studying preference reversals under ambiguity. Chapter 4 examines the influence of accountability on risk attitude. Chapter 5 is of a methodological nature. We separate accountability and incentives, and find several effects. Accountability is found to reduce preference reversals between frames, for which incentives have no effect. Incentives on the other hand are found to reduce risk seeking for losses, where accountability has no effect.