This thesis presents the process of optimizing the user experience design (UX design) by integrating psychological principles into the mobile version of a web shop, for a company called Yellow Coffee - a Specialty coffee distributer. The user experience optimization process includes monitoring the target group's behavior, alongside its psychological underpinnings. When designing an optimal user experience, human behavior is monitored according to principles of neuroscience, cognitive psychology, social psychology, and through analyzing the person-computer interaction. Almost every decision within the user experience design needs to have a sound psychological underpinning, in order to create an overall positive experience within the target group, i.e., the consumer. Principles and theories backed by psychological knowledge have significantly contributed to the process of adapting the user experience, so that specific consumer segments can be targeted more efficiently. More specifically, the major portion of this thesis is focused on the theory of persuasion, especially because of its significance for the process of user experience creation. The persuasive design uses the behavioral insights from the psychological science and applies them directly to the design process, in order to meet the user's needs more efficiently, and communicate the message more clearly. The theoretical part of this thesis covers the psychology of design, which provides the foundation for the practical part in which the mobile version of the Yellow Coffee web shop is created. The practical part of the thesis examines which type of persuasive design will influence the Yellow Coffee web shop's sales the most. Types of persuasive design analyzed and compared within this thesis include the anchoring effect, the fear of shortage, and the effect of donations.