Do YOU have a sibling? If you do, where are you in your family's birth order?
Based on the idea that general studies have found that earlier born children tend to score higher on tests of intelligence and aptitude than those born later, Robert Zajonc and Gregory Markus developed an ingenious theory to explain the relationship between birth order and intelligence.
Zajonc and Markus theorized that children who are raised in environments with greater intellectual stimulation will attain higher scores in intellectual capacities. The main point of this theory was that one's family's intellectual environment can be calculated by averaging the intellectual contribution from each member of the family. Mostly, people would have thought that the bigger the family is, the higher the intellectual environment will be. Which means that later born children will have to perform better than those previously born. However, resulted from the Netherlands study, Zajonc and Markus theorized that as family size increases, the average intellectual climate actually decreases. This is because, when one wants to find the actual confluences score for a family, the intellectual values have to be assigned to the family.
One adult values an intellectual value of 100, while a newborn infant is valued zero. So, if there is one parents with a newborn child, it will be calculated by adding (100+100+0) then dividing it by three because of the number of family members, which is 67. Once again, these are just simple arbitrary values. Therefore, if you extend this theory, this means that if there are more family members, then the intellectual level will drop. For each year, the children will be given 5 points. Therefore, if the same family has another child after two years, the calculation will be done by adding all the family members (100+100+10+0) then dividing it by 4 which is 30!
Methods & Results
By using the method both authors proposed, Zajonc and Markus developed a table that calculated the intellectual climate. They figured out that after the fifth child, the intelligence climate actually started to increase again. Which simply means that for the extremely later born children, the intelligence climate will be high for them. Therefore, there is a possibility for the extremely later born children to be smarter than those who are born first.
"Large gaps help younger children surpass older children, and they may cause a reversal in the relationship between birth order and intellect"
-Zajonc & MarkusCriticisms & Recent Applications
Usually, after the fifth child, the average intellectual climate would start to slowly increase for each additional child. Zajonc and Markus believed that this was happening because the first child and other earlier-born children are old enough to provide and boost up the intellectual climate of the family. Due to this, those children who are born late in very large families tend to benefit from not only the intellectual contributions of their parents, but also their older siblings. As the gap between two children grows, the intellectual climate for the second child would be higher than the first born because the first child would be at an age where they would add on to the overall level rather than lowering it.
However, the case is different for families with twins, triplets, and an only child. Based on several studies, twins and triplets who are born without a gap would usually perform lower on IQ tests (tests on intelligence) compared to non-twin siblings.
There were findings that did not go with the logic and ideas of the model in which Zajonc and Markus developed. It was assumed that an only-child would have one of the highest intellectual climate. Nonetheless, only-children performed more poorly compared to first born children in families where there would be up to four children. Also, Zajonc and Markus found an odd result for the last-born children.
Zajonc and Markus found one difference between an only-child and a last-born child's environment and children with younger siblings and a first-child's environment. An only-child and a last-born child is and would never be a "teacher." Based on studies, it would be best for a first-born child if the second-born child arrived within a short gap. This is because it would shorten the time that the first-born child would suffer from the lack of teaching opportunity, which is also called the last-child effect. This would be beneficial for the first-born child but not for the second child. It would be better if the second child was born after a huge gap. Usually, longer gaps are more beneficial for those families who have a lot of children. Nevertheless, huge families with huge gaps between each child would cause the siblings to spend less time together because of the huge age difference and they would share only a few interests.
The most important criticism is whether or not the difference between the first-born and the later-born child in their IQ scores are significant.
Also, there's another theory, the resource-dilution theory, that suggests that as the family size gets larger, the later-born children would have fewer opportunities for intellectual growth due to the lack of resources that are available from their parents.
There are researchers who have claimed that there is no relationship between the birth order and intelligence. They have stated, "It appears that although low-IQ parents have been making large families, large families do not make low-IQ children in modern U.S. society." Nonetheless, this is still being debated today: whether or not there is a relationship between birth order and intelligence.
It may seem like the first-born child has it all; they excel in intellectual abilities compared to their younger siblings. However, the first-born child are found to be more anxious, jealous, aggressive, and conventional compared to their younger siblings. Later-born children are found to be more rebellious, open, agreeable, and comfortable in social situations. Also, later-born children are found to be more popular with their peers and more easy-going and at ease when interacting with strangers. Last but not least, the youngest child tend to show greater originality and creativeness compared to first-borns.
IQ and Birth Order
Research done by Markus & Zajonc (Mina & Stacy)
Date of Study: 1975
Born First, Born Smarter Experiment
For More Information
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