Judith Harris’ book ‘The Nurture Assumption’ is not just about parental influence. It sets this idea in the broader context of how evolution shaped the human mind and how the child’s mind, as a result of that evolutionary history, is predisposed to categorise people — male/female, child/adult, good reader/bad reader — and to put the self into one of the categories.

For Judith Harris, one of the most important categories is that of child/adult. Her view is that children do not identify with their parents (at least not until they are old enough to become one themselves) but with a group of other children — their peers — whom they see as being them. She thinks that the main way in which peer groups shape personality is not by making everyone the same, but by differentiating among their members. Some are looked up to, some are ignored; some become followers, some leaders. All are propelled towards different roles, which are then reinforced by the group dynamics, as they sort people into different categories.

A Theory Without Evidence?

Judith Harris’ ideas are at present only a theory, yet to be backed up by research. Even then there can be no absolute truth about the precise influence of genes, parents and peers on a developing personality. Most experts in the field acknowledge that all have some influence, differing over how much and in what circumstances. Ultimately, it is impossible entirely to disentangle them all. Harris’ quest was to open the door to debate and force the establishment to re-assess what she sees as its entrenched views.

In deciding the degree of influence of a child’s peers, the power of parents (or adults in general) over those peers is also a consideration. Children do not choose the neighbourhood in which they live, the schools they attend or to some extent the friends they mix with. Parents, teachers and other adults can also affect the nature of the groups that children form. And while they may not be able directly to control the values and activities of those groups, they can nudge them in suitable directions or, indeed, in extremis, break up those groups altogether.

Personality also changes over time. A teenager who rejects the values of their parents, may return to them as an adult. A child who is anxious or withdrawn in one social setting, may be brought out of themselves and find stability in another. Nor are the groups to which as human beings we all gravitate, fixed for all time. Almost inevitably, they will overlap and alter.

An Opposing View

Jerome Kagan, professor of psychology at Harvard University, is one of Judith Harris’ most severe critics. He reminds her that:

• A recent National Institute of Child Health and Human Development research group study of 1,000 young children receiving different forms of ‘surrogate care’ found that family influences were the major cause of variation in their early social and emotional development.
• A study published in 1978 showed that working-class children adopted into middle-class homes had significantly higher intelligence scores than the non-adopted children who were genetically related to them.
• Children from different cultures have been shown to behave very differently from each other before outside peer groups can have had any effect on their behaviour.
• Studies of orphans from the Korean and Second World Wars have shown how being adopted into nurturing families had a powerful effect in determining whether the children overcame the trauma and anxiety of their experiences.

Jerome Kagan says there are many other studies pointing towards the significance of parental influence and says he knows of no culture that claims parental character and practices have no effect, and takes this ‘universal fact’ to contain a truth.