Is the exploitation of human nature and thought processes in the fields of advertising and promotion, or the use of sales strategies based on understanding human behavior, considered a forbidden act?

There is no religious impediment to utilizing an understanding of human behavior and nature for product promotion or sales strategy development. The fundamental principle regarding things is permissibility and lawfulness until a cause for prohibition arises, based on the Almighty's saying: "It is He who created for you all of that which is on the earth." Ibn Taymiyyah stated that whatever has no evidence prohibiting it is unrestricted and not forbidden.