Kijun Times

Forget the labels you assign to yourself or your children by your or their position in the sibling hierarchy. Personality traits we have long applied to firstborn, middle or the youngest children have been challenged and previous evidence found questionable, if not incorrect.

In 1928, Alfred Adler looked at children’s position in the family and claimed that birth order had a significant effect on personality. Decades later, birth order proponent Frank Sulloway advanced that position in his notable book, Born to Rebel: Birth Order, Family Dynamics, and Creative Lives (link is external). Sulloway argues that firstborns are more assertive, ambitious and conforming, while later born siblings are more adventurous and rebellious, to cite a few examples.

Psychological theory and cultural archetypes about birth order remain embedded in current thinking. Who hasn’t heard comments like these: “I can always count on my oldest, he’s so dependable”…about the youngest, “she’s so outgoing and social.” Views like Sulloway’s have been accepted as fact and held fast until now.

Birth Order Thinking Debunked

Contrary to popular belief, birth order is not an important factor in personality development. Birth order is frequently used to explain its development as well as differences in intelligence in families.

New studies find that personality is not determined by your birth order. Two large studies scrutinized what is known as “The Big Five” personality traits—extraversion, emotional stability, agreeableness, conscientiousness, and openness to experience—to determine the effect of birth order on personality development.

In the study “Examining the effects of birth order on personality,” Julia Rohrer, University of Leipzig, and her colleagues, Boris Egloff and Stefan Schmukle  scrutinized data from 20,000 adults in the United States, Germany, and England. In addition to comparing siblings in the same family (within-family design), they also looked at differences between families (between-family design). These study models, when used independently of each other, result in findings that are often questioned by researchers.

Rohrer determined that over a life’s course, “birth order does not have a lasting effect on broad personality traits outside of the intellectual domain.” She “found no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination. This finding contradicts lay beliefs” and prominent scientific theories alike, and indicates that the development of personality is less determined by the role within the family of origin than previously thought.

According to the study, the differences parents see in their children as it relates to a child’s position in the family may be more an effect of age than anything else. A younger sibling may become more conscientious with time, or as conscientious and reliable as an older brother or sister who is the firstborn. In other words, we might be calling a behavior a birth order trait when we should be wondering if it’s an age effect.

Another study, “The Associations of Birth Order with Personality and Intelligence in a Representative Sample of U.S. High School Students,” draws similar conclusions. Researchers Rodica Damian and Brent Roberts at the University of Houston and University of Illinois respectively note, “We found very small associations between birth order and personality” after looking at 337,000 students.

In a commentary titled “Settling the debate on birth order and personality,” at The Proceedings of the National Academy of Sciences, they wrote, “Scientific evidence strongly suggests that birth order has little or no substantive relation to personality trait development and a minuscule relation to the development of intelligence.”

Are Firstborns Really Smarter?

Both studies also looked at the claim that firstborns are more intelligent and found a small edge for the oldest child. Rohrer’s study reports a 1.5 point difference; Damian and Roberts, “an almost imperceptible 1 point on an IQ test in the largest case.”

They add, “Although, again, the effect sizes were quite small, we did find larger partial correlations for verbal ability (as opposed to math or spatial ability), which is in line with the predictions of the model, whereby the parental attention advantage that firstborns have, mostly consists of verbal stimulation.”  

Birth Order Labeling is Stereotyping

The birth order debate has been ongoing for decades in the scientific community. Sometimes how much weight we put on birth order is simply a convenient way to explain our children’s or our own behavior: “What do you expect? I was the youngest child.” “Of course Kelly will have everything ready. She’s my responsible one, my firstborn.”

To label children feels unproductive for developing young people and probably inaccurate. In reality, birth order is one more type of stereotyping. We know that people cling to their longstanding notions whether or not they are valid. For example, the stereotypes assigned to only children (link is external) have lingered in spite of reams of evidence that disprove them.

What is your experience with your position in the family growing up or that of your children? Do you think people will hold fast to what they have always believed about firstborn, middle, and lastborn children?