This book deals with psychological factors, which may be important for understanding the observable exchange rate movements. Thus, the study belongs to the new research field of behavioral economics, which considers the relevance of psychological factors in economic contexts. The main objective of behavioral economists is to develop a more realistic view of the actual human behavior in the context of economics. Central to the concept of behavioral economics is the assumption that humans’ actual behavior deviates from the ideal of economic rationality due to at least two reasons: first, decisions are usually based on an incomplete information basis and, second, the information processing of human beings is limited by their computational capacities. Due to these limitations people are forced to apply simple heuristics in information processing. Our aim is to analyze the relevance of simple heuristics in the context of foreign exchange markets. In our view, the decision situation in foreign exchange markets can serve as a prime example for decision situations in which simple heuristics are especially relevant as the complexity of the decision situation is very high.