Robert Dr. Robert Cialdini discusses the psychology of advertising.
Here are six principles he touches on in this great video. These 6 psychological triggers that advertisers use to get us to purchase products, make donations, and become customers are pretty common. I can look back on nearly 99% of successful marketing campaigns and identify which triggers were used. Not much really changes in advertising. This is a great video to refresh yourself on the tactics used.
6 Common Psychological Triggers In Advertising
I especially have noticed that online marketers have this psychology factor down to a T especially the Scarcity, and Authority Factors.