The ways in which humans can be triggered into making irrational decisions are many and varied. Investors make higher bids for stocks when the sun is shining. If you add paper packaging to a product wrapped in plastic, people will perceive it as being more environmentally friendly than the same product without paper. The act of sharing an article makes people feel more knowledgeable: people who read an article on investing and share it are likely to take more risk in investment decisions than those who read the same article but do not pass it on. It’s a wonder the species has done as well as it has.