This document discusses how to apply psychology principles to design in order to influence visitor behavior on social media and content marketing. It outlines three models: the Elaboration Likelihood Model, which describes central and peripheral route processing; Fogg's Behavioral Model, which says behavior occurs when ability, motivation, and triggers align; and Cialdini's principles of persuasion, like reciprocity and social proof. Specific examples are provided, like using simplicity to improve ability or rewards to boost motivation. The goal is to facilitate what visitors already want to do rather than trick them.