There’s a lot of research out there surrounding the order in which children are born. Studies indicate that firstborns hold certain advantages; for example, firstborns tend to have a higher I.Q. than their siblings and generally earn more money (whereas younger children are generally healthier).
Scientists were perplexed over the reasons behind these advantages. However, research published last week suggests that it may have something to do with how parents themselves change over the years.
The study, led by Marian Vidal-Fernandez, a senior lecturer in economics at the University of Sydney, along with fellow researchers Ana Nuevo-Chiquero and Jee-Yeon K. Lehmann, involved a longitudinal analysis of around 5,000 American children.
Here are the highlights:
- Children of higher order of birth (those born after the first child) received less quality parental cognitive stimulation, defined as “reading with the child, cultural outings, or availability of musical instruments in the house.”
- The shift in parental behavior starts early–as early as in the womb. The researchers found mothers “less likely to reduce drinking and smoking or seek timely prenatal care” in pregnancies subsequent to their first.
- Once born, non-first-born babies are breastfed less often.
These factors (among others) all seem to play a role in a child’s verbal, reading, math and comprehension abilities.
“Taken together, our findings suggest that a plausible explanation for the negative relation between birth order and educational achievement is a broad shift in parenting, especially with respect to parents’ ability to foster early cognitive development,” determined the authors.
Contrary to popular belief, though, the researchers didn’t find any relation between birth order and differences in temperament, self-confidence or behavioral problems among siblings.
What Does It Mean?
In essence, the study seems to indicate a shift in parenting styles as later children are born.
As parents battle constraints on their time, attention and energy, their priorities change. They may not feel up to the task of reading or taking their child out–at least, not to the extent that they did with the firstborn.
Interestingly, the experiment found no evidence that parents provided less emotional support to any of the children. “Parental interaction aimed at ensuring appropriate emotional development does not diminish for younger siblings,” state the authors.
So, you may not be as smart as your older sibling. But you can draw comfort in this:
When mom and dad say they love you all the same, they just might be telling the truth.
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A version of this article originally appeared on Inc.com.