Reading bedtime stories, engaging in conversation and eating evening meals as a family are seen as hallmarks of conscientious parenting.
But according to new research, while they may be positive ways of bonding with children, none of them have any influence on their intelligence.
A criminology professor has found evidence to support the argument that IQ is in fact largely down to genetics.
Professor Kevin Beaver of Florida University, examined a nationally representative sample of youth alongside a sample of adopted children from the National Longitudinal Study of Adolescent Health.
This study follows a sample of teenagers who were in grades 7 to 12 in the US in 1994, tracking them into adulthood. The last interview was in 2008 when the sample was aged 24 to 32. Using the information he collated, Professor Beaver analysed parenting behaviours and whether they had an effect on verbal intelligence as measured by the Picture Vocabulary Test (PVT).
During the test an examiner presents a series of pictures to a person.
There are four pictures to a page, and each is numbered. The examiner says a word describing one of the pictures and then asks the individual to point to or say the number of the picture that the word describes.
The IQ tests were given to the children when they were in middle school, high school and aged 18 and 26.
‘Previous research that has detected parenting-related behaviours affect intelligence is perhaps incorrect because it hasn’t taken into account genetic transmission,’ Professor Beaver explained.
Some studies have shown that parents who socialise their children by reading to them, for example, have smarter children than parents who do not engage in this way.
But others argue that intelligence is passed down from parent to children genetically, not socially.
To investigate which theory is true, Professor Beaver looked at families raising adopted children.
‘When we tested these two competing hypotheses in this adoptive-based research design, we found there was no association between parenting and the child’s intelligence later in life once we accounted for genetic influences,’ Professor Beaver said. The finding is published in the journal Intelligence.
Studying children who share no DNA with their adoptive parents eliminates the possibility that parental socialisation is really just a marker for genetic transmission, he explained.
‘In previous research, it looks as though parenting is having an effect on child intelligence, but in reality the parents who are more intelligent are doing these things and it is masking the genetic transformation of intelligence to their children.’
However, Professor Beaver stressed neglect or trauma may affect a child’s prospects.
‘The way you parent a child is not going to have a detectable effect on their IQ as long as that parenting is within normal bounds,’ he concluded.