There is a popular impression of the experimental scientist as ‘all head, no heart’! Intellectually committed to rationality, he (not usually a she) cannot afford prejudice as this will affect the truth of his scientific conclusions. This popular myth is about as mistaken as it’s possible to be. Real scientists – top-class Nobel-Prize-winning scientists – are deeply, emotionally involved in their science; they want the result to be A causes X, and they are (briefly) heartbroken if their prejudice is shown to be mistaken – usually by them, because we scientists are constantly in the position of trying to disprove our most fondly held convictions. This mistaken picture has come from the 1920s books, How to Be a Scientist and Great Experiments of the Past, which propagated the idea that science is rational, dispassionate, honest and the most successful way of finding the truth. We were confirmed in our belief that the best scientists of the previous century, like Darwin, aspired to exactly that rational, dispassionate approach.