Why do we fall in love? The neurobiologist and anthropologist, Helen Fisher, began studying love scientifically using brain scans in her research on 49 men and women. Some of the group were madly in love, while others had been rejected. Shortly thereafter, individuals who continued to be in love after three decades of marriage were included in the sample of research subjects.

According to Fisher's conclusions, the human brain has developed three cerebral systems related to relationships: romantic love, sexual attraction, and affection - or attachment: "Love can start of with any of these feelings, and it can be explained by the connections in our brain".

To date, Fisher has dedicated more time studying love from a neurobiological standpoint than anyone. She is the author of the books 'Why We Love: The Nature and Chemistry of Romantic Love', 'The First Sex: The Natural Talents of Women and how They are Changing the World', and 'Anatomy of Love: A Natural History of Mating, Marriage, and Why We Stray'.