It Von Ammon (2000) hypothesized that children born

It has been questioned whether birth order affects intellectual development. According to
a large birth order study conducted by Zajonc and Markus, 400,000 individuals were assessed on
the positive and negative effects of birth order (1975). The study consisted of nearly 400,000
participants at the age of 19. Zajonc and Markus created a model to predict intelligence based on
birth order. The results of the study showed that the rate of intelligence declined as the number of
birth order increased. The other main influence on birth order and intelligence is the spacing
between children. A large gap between children is beneficial to the youngest sibling, however, a
smaller gap is detrimental to the youngest sibling (Zajonc and Markus 1975). This means that
children born close in age are less likely to have a high intellectual environment. The study also
showed a drop in intelligence in the last child. The drop in intelligence in the last child was
theoretically caused by the child’s lack of teaching abilities. The study also included individuals
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that were an only child. It was determined that the only child does not conform to the pattern of
birth order. They did not have a greater level intelligence, however, they had the same level as
the first born in a family of four. The study provides evidence that birth order influences
intelligence levels based on the differing experiences children face in their family ranking.
Zweigenhaft and Von Ammon (2000) hypothesized that children born later in the family
are more likely to challenge authority than the first child. The hypothesis is known as the Born to
Rebel hypothesis, which states that later born children are more rebellious. The researchers
examined the birth order of a cohort of undergraduate college students who had been arrested for
engaging in civil disobedience. The students were arrested for civil disobedience due to a labor
dispute that occured over a two year span. Among those arrested were 20 college students, some
of which were arrested multiple times. For the purpose of the study, 17 of the 20 students
arrested were contacted and assessed. The study found that six of the 12 who had been arrested
one time were later borns, and that five of those who had been arrested multiple times were also
later borns (Zweigenhaft and Von Ammon 2000). Those that were arrested were compared to a
control group which consisted of college students that did not participate in civil disobedience.
They researchers hypothesis was correct and birth order correlated with rebellious attitudes
among individuals born later. This study provides evidence that later borns were more likely than
firstborns to have been detained.
The placement of birth has been theorized to influence performance on cognitive
functions and intelligence. In the study conducted by Holmgren, Molander, & Nilsson (2007),
tests of recall and recognition were used to provide evidence that birth order has an effect on
episodic memory. The participants were ages 35 to 85, however, they were retested after a five
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year interval to eliminate effects of memory loss due to disease. The study showed that later born
siblings did not perform as well on episodic memory performance as first born siblings. The
results showed significant effects for recall and recognition. This indicates that lower birth order
is associated with better episodic memory performance and recall performance is impaired with
higher birth order. Participants that were either first, second, or third born performed better when
compared to participants born fourth or later (Holmgren, Molander, & Nilsson 2007). Birth order
had a greater effect in recall tasks rather than recognition tasks. This study shows a decrease in
performance on executive functions and intelligence based on a higher birth order, there was also
an effect on working memory.
In a study conducted by Baer, Oldham, Hollingshead, & Jacobsohn (2005), 336 college
students were tested for sibling differences and were measured on creativity. The study found
that first borns from larger families were more creative when they had more siblings closer in
age to each other. For first borns from larger families, their level of creativity went up as they
had more siblings within a three year age difference. However, individuals with a greater gap
among siblings had a decreased level of creativity. Differences in sex also played a role in
creativity among siblings. Those that had siblings of the opposite sex displayed a greater amount
of creativity. Growing up with a group of siblings of the opposite sex seems to positively
influence creativity in first born children. Older boys and girls with siblings of the opposite sex
were more curious and displayed more interests (Baer, Oldham, Hollingshead, & Jacobsohn
2005). Sex differences among smaller families did not hold the same results, meaning the greater
the family, the greater the influence of birth order. The results of the study show that birth order
as well as siblings of opposite sex have an effect on creativity.
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There is evidence that supports the effects of birth order among individuals. Certain
personality traits are given to a member of the family based on their rank. There are also theories
to support why an individual may hold traits that reflect their birth order. For example,
intelligence levels among families with more children may be a result of the children being
surrounded by family members with lower IQ’s. It was also suggested that families with lower
intelligence tend to have a greater number of members. Lastly, children that were born last have
the lowest levels of intelligence because they did not have to assume a “teaching” role. The
eldest sibling has been linked to being the leader of the other siblings. They also have more
responsibility in the family.
According to the Born to Rebel theory introduced by Frank J. Sulloway, individuals that
are born later in the family tend to rebel. These individuals may challenge authority because they
were born after multiple siblings. Possible reasons they rebel can be due to lack of discipline or
the need for attention. Usually in larger families it is difficult to discipline the youngest child, or
the child later born. It is a trend in families that the first born is given the most discipline,
however, by the third or fourth child the discipline gets weaker. There may also be more conflict
with parents or other family members which leads them to rebel. The Born to Rebel theory was
also applied to leaders of movements and revolutionaries throughout history. Those that rebel are
more likely to be a later born child.