This thesis is made up of three Chapters. In the first chapter, “Happy, healthy, wealthy and rational: Are biases harmful?” I conduct a quasi-experimental survey to investigate whether or not five biases and fallacies (present bias, sunk cost fallacy, loss aversion, gambler’s fallacy and impact bias) affect the likelihood of depression, of an individual participating in socially (un)desirable behaviors and whether or not they are associated with lower incomes. Out of the five biases investigated three are linked to lower incomes, but only one to a higher likelihood of depression. In the second chapter, “The Marginal Benefit of Manipulation: Investigating paternalistic interventions in the context of intertemporal choice”, I conduct an experiment to determine to what degree a traditional libertarian paternalist (LP) intervention, popularly known as a nudge, can outperform an autonomy-enhancing paternalist intervention (AEP). I introduce the term Marginal Benefit of Manipulation, MBoM, defined as the difference in treatment effect between an LP and AEP intervention. I find that the AEP intervention completely failed to alter behavior, but while the LP intervention fares better at first, it tapers off towards the end of the survey and the treatment effect becomes insignificant. In the third chapter, “The Marginal Cost of Transparency: Do honest nudges work?”, I conduct another experiment, this time to determine the effect that transparency has on the efficacy of a nudge. I introduce the term Marginal Cost of Transparency, MCoT, defined as the difference in treatment effect between a libertarian paternalist intervention (LP) and what I call a transparent libertarian paternalist (TLP) intervention, a type of LP intervention where consumers are made aware of the nudge and why it is there. My results indicate that the MCoT is, with few exceptions, not statistically different from zero and that the answer to the question “Do honest nudges work?” is Yes. Furthermore, the results indicate that autonomy-enhancing paternalism fares at least as well provided participants are paying full attention.