Most of us know by now that men and women are different. Yet it is not the differences that cause distress in our relationships. It is what we have in common: programmed, biological responses that are as unconscious as blinking. The primitive part of our brain pierces us with Cupid’s arrow and we fall in love. It then rips the arrow out ... Our perception of each other – and behaviour towards each other – changes for the worse. Remarkably, such diverse symptoms as selfishness, infidelity, unfulfilled needs, lack of communication, nagging, addictions and sexless marriages all originate in these unsuspected commands.