A large experimental and empirical literature on asymmetric dominance and attraction effects shows that the probability that an alternative is chosen can increase if additional alternatives become available. Hence context matters and choices and, therefore, market shares can not be accurately described by standard choice models where individuals choose the alternative that yields the highest utility. This paper analyzes a simple procedural choice model. Individuals determine their choice by a sequence of binary comparisons. The model offers an intuitive explanation for violations of regularity such as the attraction and the asymmetric dominance effect and shows their relation to the similarity effect. The model analyzes a new rationale why context matters. The model is applied to explain primacy and recency effects and to derive implications with respect to product design.