Websites using perceptual difference as a keyword

Free puzzles, riddles, brainteasers, lateral thinking problems, spot the difference pictures, advanced puzzles for geeks and brainiacs, and a monthly puzzle contest.

Covert Communications delves into the theory and practice of the sales pitch, propaganda, covert influence, marketing, advertising, salesmanship and powerful persuasion techniques/tactics. It has tutorials on NLP, hypnosis, persuasion, salesmanship, how to influence people, persuasive writing and propaganda. It also features articles involving all of the above topics as they apply to current events in the news and how covert communications from various channels influence the way you think, what you buy and what you expect from life.