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The Birth Order Effect

What is the birth order effect?

Birth order refers to the position of a child in the family relative to their siblings. It has been proposed that birth order influences the development of personality and intelligence. Whether a child is born first, in the middle or born last can affect how parents and siblings interact with them. The personalities of all children within a family are distinctive due to their unique experiences. While one may argue that all children within a family have the same experiences dealing with their parents and siblings, it has been found that this is not the case. It is not the birth order in itself which explains these differences in personality. The psychological situation which results from ones position within the family accounts for the variation. Certain characteristics have been identified that are more likely to be seen in children of certain family positions. The most differences are usually seen between first born and later born siblings.


Interest in the birth order effect is not a new occurrence. More than a century ago Sir Frances Galton observed that a large number of first born sons and only male children occupied positions as British scientists. Galton believed that first born children, especially first born sons were favored by their parents. At the time primogeniture was the norm where the family fortune was inherited by the first born son and he had the responsibility of taking care of other family members. First born sons were therefore given the greatest responsibility. High education was expected of the first born sons of upper class families, which explains why more first born sons are seen in science related positions. Alfred Adler was the first to link ones position within family to the development of personality. Adler believed that although primogeniture was no longer widely practiced birth order still exerted an influence on development.

Alfred Adler

Alfred Adler, a personality psychologist, was born in Vienna in 1870. He was the second of six children born to a middle class Jewish family. In 1895, Adler graduated from the University of Vienna with a medical degree. He began his career as a general practitioner and later moved on to the field of psychiatry. In World War I he was an Army physician. Alder also held political office as the Vice Chairman of the Worker’s Committee of Vienna. Adler’s main theory of personality was that humans are motivated by social urges. He published 100 books and articles in his lifetime outlining his theories. Adlerian Clinics were set up in 30 state run schools between 1921 and 1934. These clinics were operated as mental health facilities. The clinics were shut down in 1934, the same year Adler fled to the US to escape Nazi infested Austria. Soon after, Alder died in Scotland in 1937 while on a lecture tour.

Adler’s Personality Theories

According to Adler there are three important influences on personality. The mother is the most important determinant in the development of her children’s personality. The father is the second most important influence, while the third is the birth order.

What Birth Order Effect Patterns have been identified?

Researchers have found strengths and weakness that are inherent in birth order positions. Lucille Forer (1977) has found from clinical practice that birth order effects are generally predictable. However she does note that it is not so much one’s position in birth order alone but one’s experience within the family that is critical. This experience is often affected in similar ways among families by being the oldest, middle, youngest, or only child. One’s experience may also be affected by gender roles within the birth order sequence and by the number of years children are separated from their siblings. It is also important to remember that birth order effects are not absolute or irreversible, and it is possible to actively change one’s viewpoints, attitudes, and lifestyle (Forer, 1977). Despite this there are definite patterns of typical behaviour exhibited by only children, and the oldest, middle, or youngest child. Walter Toman (1993) notes that eight types of sibling positions have been identified and explored. These are: the oldest brother of brothers, the youngest brother of brothers, the oldest brother of sisters, the youngest brother of sisters, the oldest sister of sisters, the youngest sister of sisters, the oldest sister of brothers, and the youngest sister of brothers. Sibling positions can combine in some fashion in multiple sibling positions, for example a child who has younger sisters and brothers. According to this model a person holding a multiple position may show characteristics that correspond to two or more of the basic types of sibling relationships. Bossard (as cited by Forer, 1977) has categorized the types of children usually found within a large family: the responsible one, the popular and well-liked, the socially ambitious, the studious, the self-centred loner, the irresponsible, the physically weak or ill, and the spoiled child. Although he cautions that these categories are not fixed or universal, and that a family with eight children will not necessarily have a child to match each category.

The Only Child:

Only children are affected by the fact that they go without experiencing sibling relationships. The only child’s main contacts are his parents, with whom the child does not have to compete with siblings for time, attention, and affection. This has positive and negative results. Because the only child doesn’t experience sibling rivalry they are typically less anxious, more mature, self-sufficient and optimistic than children in other birth positions, and may develop a high level of self-confidence. However, depending on their relationship with their parents they may have internal dependency conflicts concerning their parents. They may also experience loneliness. The only child also has a disadvantage in contact with peers because they have not been able to practice interacting with other children.

The Oldest sibling:

The oldest child is usually conservative and self-controlled, reflecting his or her parents’ customs and attitudes. The oldest child is more likely to be jealous and anxious than his or her sibling(s) as a result of being forced to share the parents’ attention which was previously reserved for the oldest child before the siblings’ birth(s). Socially the oldest child is typically respectful, conforming, and responsive to authority. He or she seeks approval and because of this is susceptible to social pressures. The oldest child is typically a high achiever and achieves more distinction in professional life than his or her younger sibling(s). They tend to hold more positions of political leadership (Andeweg & van den Berry, 2003) and are over represented in Who’s Who (Hetherington, Parke, & Schmuckler, 2005). Although they are often seen as being favoured by their parents they may be dissatisfied with themselves because so much is expected of them as children, and often have moods ranging from sensitive seriousness to depression as a result (Forer, 1977).

The Middle Child:

Children born in the middle can either be born between two other children, or may come from families with more than three children, which will affect the child. Whether they are an “older” or “younger” middle sibling may determine if they develop characteristics more closely resembling their younger or older siblings or parents (Toman, 1993). The child who is born between two other siblings is often considered to hold the most difficult position. He or she is placed in a position that stimulates the most competition (Forer, 1977. In a survey of three-child families children and their teachers agreed that the middle child seems the most vulnerable to maladjustment. Among nursery school children second middle children were rated highest on verbal aggression towards peers and on seeking help from adults (McGurk & Lewis, 1972, as cited from Forer, 1977). The second of three is more excitable, demanding, attention getting, and undependable. Middle children may feel overlooked or excluded in the family which leads them to leave the family earlier in life and move farther away. However, he or she does have the advantage of getting practice with negotiating him or herself with different types of people.

The Youngest Child:

The youngest is often characterized as being charming, lighthearted, and playful; and because of this are often more popular than their sibling(s). They are seen as “the baby” by family members which may result in special privileges, such as having the parents dote on the child, especially in a small family. The youngest child is affected by whether they are the younger of two children or the youngest in a larger family. In a larger family the youngest may go unnoticed because of the busyness of the family. The youngest is usually placed in a position of one of two extremes: being the family pet or suffering from teasing from older siblings. Regardless, the youngest child often is more dependent upon others than other children because he or she is use to having to someone older (a parent or sibling) to help solve problems. They tend to have a low acceptance of responsibility, but are good at compromising.

The Mother

As proposed by Adler, the mother is the most important influence on the development of her children’s personality. Before birth the mother can have an impact on the health of her children. As the mothers age increases with subsequent births the chance of genetic defect such mongolism and Down’s syndrome increases. A second born child is usually healthier than a first born even for women of the same age. With the first born the labour is longer which can have an effect on the child. Mothers of later born children usually have less labour complications.

Parental Attitudes

Parental attitudes toward the birth of a child change with subsequent births. Parents tend to react differently toward their first born children then they do toward their later born children. The ways in which parents interact with their first born children change as more children are born. These differences can be attributed to the physical aging and the psychological aging of the parents. A mother who has had her first born at the age of 25 and her last born at the age of 40 will not have the same physical strength and endurance to give to all children. Parental attitudes change with experience. Parents may be stricter in disciplining a first born. First born and only children for a time period are the centre of their parent’s attention. With later born children the parents may provide less attention to each child which means that the needs and achievements of later born children may be over looked. Later born children may also seem like more of a burden. The personality of first born children is more likely to be shaped by parental influence than the personality of later born children. First born children grow up in an adult centered atmosphere and therefore are more likely to be shaped by their parents. Later born children grow up in more of a children centered atmosphere and are therefore more likely to be shaped by the influence of their siblings. The personality and health of the parents also influence their children’s personality. Parents tend to discipline their children differently depending on their birth order. Parents are usually the strictest with their first born children. Younger children tend to use the experiences of their older siblings to avoid serious discipline. First born children tend to be very serious as adults as a result, while younger children learn to be manipulative as they get older.

Sibling Interactions

Research has shown that interactions among siblings (whether positive or negative) can influence each child’s behaviour, learning, development, and personality. When the first child is born they have the undivided attention of their parents and therefore have full power. Once the second child is born tension develops as the first born realizes they are no longer in full control. To accommodate for the loss of power, first born children exert power over their younger siblings. If the oldest child is stronger, exerting power may include the use of physical strength over younger weaker siblings. Younger children tend to use more devious ways of obtaining what they want to avoid backlash from older siblings. In this sense all children within a family become rivals of one another, all in competition to attain power and parental favoratism. Younger siblings may be more aggressive to counteract the bossiness of older siblings. Children reward and punish one another as a means to meet their own needs. If a younger sibling obeys their older sibling, the older sibling will be nice to the younger. On the other hand though, if the younger sibling is assertive and does not obey the older sibling, the older will punish the younger. Younger children can punish their older siblings as well by complaining to an authority figure such as an adult. While these patterns of behaviour are common in early life sibling interactions do tend to change over time. It is these interactions between siblings based on their birth order which trains each child to take on certain patterns of behaviour. The patterns of behaviour which develop lead to the formation of personality and behaviour in later life.

Does the Age Difference between Siblings have an impact on Birth Order Effects?

However, Toman (1993) notes that the larger the age distance between siblings, the less the siblings will affect each other. When the younger sibling is born two to three years after the older the latter sees his sibling as a rival for the care, attention, and affection of the parents, as well as for gifts and even food. When the gap is three to four years these things are less important. Now the older sibling feels threatened in his power and control over his parents. When the gap is four to five years the older child has learned to respond to others’ sex. Therefore there is still an atmosphere of competition with others of the same sex, but there is a tender atmosphere with those of the opposite sex. So, the sex of the new sibling will play a large role in their relationship. It is best if the sibling is of the opposite sex. If the age gap is more than six years the older sibling is not largely affected by the younger sibling. The older sibling is already going to school and is more independent. Siblings who are six or more years apart tend to become “quasi-only children” unless they have other middle siblings closer in age in-between them. A middle child is likely to be more influenced by his or her sibling closest in age.

What about the Sex of Siblings?

Along with age Alfred Adler suggested that the sex of siblings is important in the way a child adopts his or her sex role. For example a boy reared only with girls may either be strong and assert his masculinity or he might be weak and non assertive; or a girl reared with male siblings may go through life feeling insecure and helpless. Forer (1977) identifies typical sex role patterns associated with each birth order position. Firstborns tend to turn to the father for attention after the second child his born because the baby needs the mother’s attention. Because of this firstborn males have a greater opportunity to identify with masculine roles than girls do with feminine characteristics. The only child may adopt sex-role characteristics from both parents. One danger for the only child is the possibility of forming too close an attachment for the opposite-sex parent. In families with two siblings Forer finds, “The combination of an older brother with a younger sister seems to cast the most clear-cut sex role for each according to society’s view of males and females… If the family contains an older sister with a brother the girl may develop easily as a female, but the boy may not have a comfortable feeling about his masculinity because his sister seems stronger and more adequate”. In families with two girls both tend to be relatively feminine. Middle children in larger families generally find their sex-role identification in the give and take among brothers and sisters, and parental attitudes. Helen L. Koch (1956) from the University of Chicago conducted a study of “sissyness” and “tomboyishness” among six-year old children. She found that girls with brothers two year or more older were relatively “tomboyish” while second born males with sisters were relatively “sissy”. She also found that age difference was important. Boys seemed to be less sissy as the age difference between them and their older sister increased.

A Survey of Scientists:

Sulloway (1990) asked scientists (2,784 in total) if they accepted or rejected new scientific theories. There were twenty-eight scientific controversies they were asked about, such as the Theory of Relativity, Freudian psychoanalysis, and mesmerism. He found that birth order correctly classifies sixty-fiver percent of the supporters and opponents in four centuries of diverse scientific debate. New theories were supported more strongly by later borns than firstborns. Sulloway also accounted for such variables as politics, religion, age, nationality, sex, and education. Birth order was the best single predictor of a person’s acceptance of or resistance to scientific innovations.

Toman’s Systemic Approach to Research:

Toman uses a systemic approach to research, which means he interprets combinations of two or more family constellations characteristics and if possible interprets many or all of the characteristics he can gather through interviews with the client. In most cases it leads to a better understanding of a family than any other diagnostic instrument. He says, “Single characteristics of a family constellation… at best only explain ten to twenty percent of the variance of a person’s long term social behaviour… eighty to ninety percent, and even more, of the influence on behaviours comes from other sources, such as education, ethnic or religious background, physical appearance or special talents, etc.” However, using his systemic research method he had found that the percentage of variance of the long-term social behaviour may rise to fifty percent or better.

Linking Birth Order to Political Leadership- Andeweg and Van Den Burg (2003)

Research has shown that being a first born or only child increases the likelihood of attaining a public office. First born children are over represented in many political offices such as U.S state governors, U.S. presidents, within the U.S. congress, and as Australian prime ministers. It is unlikely that a particular birth order in itself can account for this trend, but rather the unique set of experiences that a first born child is exposed to that readies them for a career in a public office. Differing birth order experiences can be attributed to parental impact as well as sibling interactions. Andeweg and Van Den Burg (2003) tested both these hypotheses separately (although not ruling out the combined effect) to explain the overrepresentation of first born children within political roles. The parental impact hypotheses were that: 1.) First born and only children are overrepresented, while middle and last born children are underrepresented in political offices, 2.) First born males (regardless of having an older sister) will be overrepresented, and 3.) This effect is seen more so in older generations. The sibling interaction hypotheses were that: 1.) First born and only children are overrepresented, while middle and last born children are underrepresented, 2.) First and middle born children will be overrepresented regardless of sex, and 3.) First and middle born children are overrepresented regardless of generation. For this study data was collected on 1200 politicians from the Netherlands through a mail questionnaire. Andeweg and Van Den Burg found that first born and only children are overrepresented within political offices, while middle born and last born children are underrepresented indicating that parental impact has the greatest effect in determining political leadership.

Rohde et al. (2003)

Rohde et al. (2003) proposed three determinants to explain the differing interactions of parents with their children based on their birth order. The first is the reproductive value of the child which depends on the age of the child and parental investment. First born children rank the highest on reproductive value. The second is neediness, in which last born children rank the highest. The third determinant is the mother’s reproductive potential which leads to maternal care being directed toward later born children. This study used these three determinants to test the hypotheses that: 1.) In families with two children the first born child is usually closest to their parents, while in families with three or more children the middle child is usually the least close to either parent because they do not rank very high on reproductive value or neediness, 2.) In families with three or more children, middle born children will be the least favored, 3.) In families with three or more children, the middle child is the most likely to rebel, and 4.) Women tend to feel closer to their siblings then men do. Data was collected for this study from 2024 university students from Austria, Germany, Israel, Norway, Russia, and Spain through questionnaires. Rohde et al. found that the rebel of the family was reported to be the last born child in families with two children, while in families with three or more children the rebel was the middle born child. In families with two children, the last born child reported being the favored child. In families with two children first born children reported feeling closer to their parents, while in families with three or more children the middle born child was the least likely to feel close to either parent. They also found that both sexes felt closer to the same sex parent, while women feel closer to their family during times of crisis.

The Role of Birth Order Effects in a Marriage:

Birth order effects can also be seen in adults. Toman looked at the sibling position of individuals who were parents and found that those who were complementary did not have a single incidence of divorce. Those who had a rank and sex conflict had a divorce rate of sixteen percent. The overall rate of divorce among parents of the generation studied in the early sixties’s was five percent both in the official population census and in Toman’s sample. His sample size was 2300 Swiss and German families. Couples who would be considered complementary are: fathers who are the oldest brother of sisters married to a youngest sister of brothers or fathers who are the youngest brother of sisters married to the oldest sister of brothers. Couples who have a sex and rank conflict are: fathers who are the oldest brother of brother married to the oldest sister of sisters or the same only both are the youngest instead of oldest in the family.

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