This dissertation investigates the causes of the bullwhip effect by conducting a systematic literature review and two empirical studies. The bullwhip effect is characterized by a distortion of demand information that propagates in the upstream direction of supply chains, causing severe inefficiencies such as excessive inventory investment and lost sales. Previous research has already produced numerous publications on the bullwhip effect, especially on its causes, but a systematically derived up-to-date compilation of the causes is missing in the literature. Therefore, in the first part of this dissertation, the causes of the bullwhip effect were systematically compiled from existing publications and inductively categorized. The second part of the dissertation addresses the observation that individuals differ greatly in decision-making and add to the bullwhip effect to varying degrees. To contribute to the literature on why and how decision-makers behave differently in a supply chain context, two laboratory studies were conducted examining the relationship between thinking orientation (holistic versus analytic) and the bullwhip effect.