The large family is unavoidably hectic, chaotic and competitive, but this rich 'rough and tumble' has always been viewed as a good thing, giving children a complex and challenging environment in which to hone their social skills ready for the real world. It is however, widely accepted that whenever a child is added to a family, parental time is stretched a little thinner leaving less time for each individual child. That means less affection, less reading, less throwing a ball, less help with homework and less one on one time to talk about deeper issues. But it has always been assumed that this quantity for quality trade-off was of no lasting significance and easily paid back by the sibling advantage. Well, new research from the National Bureau of Economic Research in the US, has found this isn't the case.
The research lead by Chinhui Juhn from the Department of Economics at the University of Houston was based on mothers from the National Longitudinal Survey of Youth 1979 and their children in the corresponding Children and Young Adult Survey. The data contains detailed information about childhood cognitive abilities and non-cognitive traits as well as measures of parental investment and home environments. In all 4,925 mothers and 11,464 children were interviewed. Children were surveyed biannually from 1986 to 2012.
Researchers set out to explore whether there was a quantity quality trade-off for adding siblings to a family. They found that while it is small, it is there: "Increases in family size decrease parental investment, decrease childhood cognitive abilities, and increase behavioral problems. " The biggest decrease in cognitive abilities was found in girls while boys demonstrated a larger decline in behaviour.
The researchers also set out to test which of four forms of parental investment was most significant: time, resources, affection and home safety.
Parental time was defined through a number of questions to the mothers in the original survey: “How often do you read stories to child?” “How often has a family member taken or arranged to take child to any type of museum?” “How often does child eat a meal with parents or caregivers?
Resources were determined though questions about access to recorded material for children, newpapers, books and musical instruments in the home. Parental affection was based on questions regarding physical affection, tone of voice used when addressing children and conversations. Homes safety related to the home environment, whether it was clean, dark, decorated, dangerous or cluttered.
The results showed that parental time was the factor that most influenced children's cognitive and beahavioural outcomes and the reduction in time spent with a child after the arrival of a sibling was the cause of a measurable decline.
The research supports the idea that parental time is critical to the cognitive and behavioural development of children and that as siblings are added this important parental resource is inevitably stretched.
It's true that you would expect the birth of an additional child to weigh on parental time but you'd think the negative effects would soon dissipate. The research showed the opposite to be true.
"Not only do we fail to find evidence that the impact is transitory, effects appear to substantially worsen over the longer run. Test scores and parental investments are both worse over the longer horizon than in the short run."
We can only speculate as to why this would be. Perhaps parents pull back from interacting with their children as they grow older and become more self sufficient. Mothers return to full time work, children spend time with friends and in their own rooms, parents seek out time alone. The children may well prefer to spend spend time with eachother rather hanging out with their parents.
This research paper adds to a growing body of work that seeks to prove or disprove what
economists call the "quantity quality trade off." It's a debate about family size and whether big is better, or less is more. This debate folds into another about birth order, since if all children aren't treated equally, it effects the discussion of size by scewing resources towards the top end.
"...significant birth order and family size effects in individuals’ years of education thereby confirming the presence of a quantity-quality trade off."
Children living with siblings had reduced educational outcomes overall, and since the first born tends to experience higher levels of education having spent most time in a smaller family, receiving a greater share of parental resources and time, the outcomes for the later born children were worse.
The results of this research are backed up by another study "Birth Order Matters: The Effect of Family Size and Birth Order on Educational Attainment" which analysed family background data from the 2003 British Household Panel Survey to explore the degree to which family size and birth order affect a child's subsequent educational attainment. They found that " children from larger families have lower levels of education and that there is in addition a separate negative birth order effect."
The study supports a growing body of research that indicates a family's educational resources are not shared equally amongst children and that children's share of those resources decrease with birth order.
But do the advantages bestowed on first born children convert into improved earnings later in life? The answer is potentially yes. In a study by the Institute for the Study of Labor at the University of Bonn entitled "Birth order, educational attainment and earnings: an investigation using the PSID" researchers found that "Being first-born confers a significant educational advantage that persists when considering earnings; being last-born confers none."
So as you'd expect, the cognitive and educaitonal advantages conferred on first borns translates into increased earning later in life.
All these studies have been conducted by economists and for good reason. Governments are keen to know whether family size is something they should be encouraging or not through the economic levers at their disposal such as taxation, parental leave and childcare subsidies.
But for parents a message is emerging, more children will inevitably lead to inequality amoungst them and a diminished quality of parenting for all.
As someone who advocates for the benefits of the 'only child' and the enormous potential of Generation Only I see these studies as real emerging scientific support for the idea that only children, being both first born and in the ultimate small family, are both cognitively, behaviourally and educationally advantaged.