Subtitles section Play video Print subtitles It's time to talk about the psychology of persuasion. A few years ago researchers approached houseowners and asked them to place a huge sign saying 'Drive Carefully' in their front gardens. Everyone refused. The researchers then approached a second group, and asked them to place a small 'Drive Carefully' sign in their gardens. Almost everyone agreed. Two weeks later, the researchers asked those in the second group to replace the small sign with the large one, and an amazing 76%of people accepted. Psychologists call this the 'foot in the door' effect - agreeing to a small request makes people far more likely to then agree to a much bigger one. So, if you want to persuade someone to do something, start small before moving big.