Conversion optimization is a matter of persuasion. And persuasion is, first of all, a matter of psychology. As you may know, nobody is better than Robert Cialdini in teaching us about persuasion and psychology as a way to understand how customer's mind works.
Not surprisingly, marketers regularly base promotional techniques on Cialdini's principles of social influence to increase the desirability of their products among customers. The choice of what tactics to use, however, is primarily determined by their business goals, while ‘who’ their customers are - from a psychological point of view - is often pushed into the background.