Netherlands Television Interview with Robert Cialdini. P0 Introduction part 2 - Cialdini. Principle 6 Liking part 2 - Cialdini. Principle 6 liking part 1 Cialdini. Principle 5 consensus 5:09 minutes. Principle 4 consistency 8:26 minutes. Principle 3 authority 9:20 minutes. Principle 2 scarcity 8:51 minutes. Principle 1 reciprocation 9:23 minutes. Robert Cialdini - Renowned Expert in the Psychology of Influence, Negotiation & Communication.