24 April 2010 | NewScientist | 47

How we shape upWe are born with a temperamental bias, but biology is not destiny, a new book argues

The Temperamental Thread: How genes, culture, time and luck make us who we are by Jerome Kagan, Dana Press, $24.95

Reviewed by Michael Bond

ANYONE who still believes that our psychological dispositions are due largely to our genes will learn a lot from this book. The same goes

for those who think they are predominantly shaped by our environment. Jerome Kagan, an emeritus professor of psychology at Harvard University, has spent much of his career unpacking the complexities behind human personality and behaviour. In The Temperamental Thread he navigates a path through the conflicting evidence with great skill and eloquence.

The thesis behind the title is that everyone is born with a biologically based temperamental

bias that is evident in infancy and influences our future behaviour, but how that pans out as we grow up depends strongly on a range of factors such as our ethnicity and gender, how our parents treat us, their social class, the size of our home town and whether or not we have older siblings. Temperamental bias, he explains, resembles the inherited components of a bird’s song: “Although the bird’s genes contribute to the basic components of the song, they do not determine the specific songs the adult bird will sing.”

Kagan’s expertise derives partly from an exhaustive longitudinal study in which he followed the lives of more than 450 people from 16 weeks old to adulthood. He found that those who become distressed or strongly aroused as infants when confronted with unfamiliar objects, such as brightly coloured mobiles, tend to grow into timid or anxious adolescents, while less reactive

infants develop a more relaxed, spontaneous disposition.

However, he stresses that these outcomes are not fixed since the developmental environment can powerfully distort the effect of genes. For example, while the possession of a gene variant which disrupts serotonin activity in the brain can result in social anxiety in a woman raised in a stable middle-class family, it can contribute to criminality in a man brought up in poverty by abusive parents.

This kind of analysis leads Kagan into some interesting areas, such as the origins of psychological differences between the sexes and between members of different ethnic groups. He is also happy to throw in the occasional wild speculation, such as the idea that women are better placed than men to save the world from ecological disaster.

None of this undermines the serious messages in his book, perhaps the most important of which is that we are still largely ignorant about the biology that underlies behavioural predispositions and the cascade of psychological processes that flow from them.

Do the mathAlex’s Adventures in Numberland: Dispatches from the wonderful world of mathematics by Alex Bellos, Bloomsbury, £18.99

Reviewed by Celeste Biever

THERE are children in Tokyo, trained in after-school abacus clubs, who can sum up to 30 large numbers using only the mental image of an abacus,

and do it faster than someone with an electronic calculator. And there’s a mathematician in New York whose intricate crocheting has allowed her colleagues to visualise various surfaces in hyperbolic space for the first time. These are

some of the delightful characters that populate Alex’s Adventures in Numberland.

As well as describing his interactions with a range of brilliant minds, Bellos careers lucidly through the most mind-boggling concepts with which they grapple. Some beautiful explanations include why infinity comes in different sizes and why Euclid’s postulates only hold for flat space. The end result is a page-turner about humanity’s strange, never easy and above all never dull, relationship with numbers.

Dream machineLeonardo’s Legacy: How da Vinci reimagined the world by Stefan Klein, Da Capo, £14.99/$26

Reviewed by Jonathan Beard

WHEN we think of Leonardo da Vinci, it is usually the Mona Lisa or The Last Supper that spring to mind, but from a scientist’s perspective, it is

the thousands of drawings the Italian genius left behind upon his death in 1519 that are his greatest legacy. Science writer Stefan Klein examined the original drawings in public and private collections, including the Queen of England’s collection at Windsor castle.

Klein outlines a life dedicated to study and speculation about anatomy, flying machines, weapons and hydrodynamics. The astonishing drawings showing the flow of water underline the power of da Vinci’s visual imagination, and his limits as an engineer: almost entirely self-educated, he never mastered long division, much less the higher mathematics he would have needed to explain his inventions.

Though Klein sometimes overreaches when he speculates about da Vinci’s thoughts or religious ideas, he provides an engaging introduction to da Vinci’s life and scientific interests.

For more reviews and to add your comments, visit www.NewScientist.com/books-art

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