Do unto others as they do unto you" and "I'll scratch your back if you scratch mine". These and many other aphorisms capture the reciprocal nature of co-operative human interactions. But why do we play nice? This question is especially apt with the never-ending news of murder, terrorism and war. Indeed, is human nature, at its core, "naughty" or "nice"?
In The Neuroscience of Fair Play, Donald Pfaff, an eminent neurobiologist at the Rockefeller University in New York City, develops a theory of good and bad behaviour. The story is woven mostly with tales of tails - much of the research he presents to develop his theory of human behaviour is based on studies of rodents, including research from Pfaff's own lab. Using rodent studies allows great detail in the development of the theory, from genes, to brains, to behaviours.
Pfaff's theory is built on recent findings showing that human beings have neural mechanisms that make us care about others. These systems generate empathy by making us literally feel another's pain in our own brains. This mirroring of emotion often motivates us to alleviate the other's distress.
The key molecule inducing empathy is called oxytocin, a simple chemical ancient in origin that, as my lab has shown, motivates us to care about others - even complete strangers. Oxytocin released in the brain modestly moves the balance between distrust and trust of others towards the latter. It is trust that causes us to play fair.
Pfaff explains the mechanisms through which other chemicals, including some gendered favourites such as oestrogens and testosterone modify the oxytocin-empathy-fair-play triad, and how this occurs in the brain. Nearly half the book describes the neurobiology of failed empathy systems that lead to "murder and mayhem".
For those interested in the biology of behaviour in human and non-human animals, Pfaff provides a feast of tightly woven facts at a middling level of detail. I suspect there may be too much detail for some general readers, as the text occasionally gets bogged down. One could, though, skip the middle chapters and still have a good sense of the biology of fair play.
Scientists such as myself who work in this area will enjoy the extensive integration of findings across fields, although applying some of the findings in rodents to humans can be problematic. Indeed, important research studying the human brain while moral and reciprocal decisions are made is mostly absent in this book.
Pfaff also ignores the role of cultural institutions on fair play. In a recent survey, two thirds of Norwegians said that their compatriots could be trusted, while only 2 per cent of Brazilians believed that their fellow nationals were trustworthy. In laboratory studies of trust, Scandinavians are indeed much more likely to trust strangers than people of other nationalities. Why? Research by my lab and others has shown that environment matters, but this is not discussed in this book except obliquely.
So what makes us play nice with others? When we encounter someone whom we judge to be trustworthy, brain mechanisms using oxytocin motivate us to cooperate with them. In stressful or conflictual environments, these mechanisms are inhibited, leading to isolation, selfishness and even immorality. Although there is substantial variation across people in the mechanisms supporting fair play, Pfaff argues persuasively that nearly all humans have the capacity for empathy and this is an essential component of our human nature.
There is a simple test for this: I bet you were so engaged with fictional characters in a movie you saw recently that you cried. That's the empathy response, and you know how difficult it is to stop this. Pfaff will tell you why.
The Neuroscience of Fair Play: Why We (Usually) Follow the Golden Rule
By Donald W. Pfaff
Published 4 January 2008