In The Hitch-hiker’s Guide to the Galaxy the author, Douglas Adams, describes a planet inhabited by a race of hyperintelligent pan-dimensional beings who build a hyperintelligent computer to help them come up with the answer to Life, the Universe and Everything. After many millions of years of deliberation this machine finally delivers its verdict: the answer is forty-two. Naturally the heirs to the computer-builders are somewhat disappointed about this. After all, one expects better value for money for one’s computer time. In its defence the computer points out that the problem lies not in its answer but in the question it was asked in the first place. In order to understand the answer they first have to understand what the question really means, and that, they are told, will require an even more powerful computer! All of which is a roundabout way of saying that what matters in this world is asking the right questions, rather than knowing the right answers. It is in this spirit that this book is intended to add to your education in psychobiology. It is a book that focuses on the questions that psychobiologists ask, rather than on the answers that they give to them. It is concerned with telling you as much about what we don’t yet know as about what we do know.