Alfred Adler, an early psychoanalyst, and contemporary of Sigmund Freud, was the first to theorize that birth order affects personality. According to Adler, your personality is directly influenced whether you’re the youngest child, oldest child, or somewhere in between.

Note that birth-order studies are mainly correlative. And – as it’s important to understand – correlation does not equal causation.

Studies on birth-order suggest that, compared to individuals born later, firstborn children tend to be more:

• Achievement-oriented
• Intellectual
• Likely to become social leaders
• Stubborn
• Conservative
• Ambitious

Overall, research shows firstborn children to be less compliant than children born later, while younger children – the babies of the family – tend to be less independent, and more:

• Social
• Spoiled
• Immature
• Irresponsible
• Attention-seeking
• Rebellious

That’s what the research says about firstborn and youngest children. However, as we all know, there are millions of children that are neither. They’re somewhere in between.

What About the Middle Child?

Adler’s theory was that middle children, due to their place in the family birth order, generally feel overshadowed. Since the first child is more likely to receive more responsibilities, and the youngest child is more likely to be pampered, this leaves the middle child with no clear role or status within the family. Since they’re sandwiched between two (or several) children, they feel left out and neglected. This effect is called middle-child syndrome.

In fact, a literature review analyzing about 200 studies on birth order and personality found that it’s very common for middle children to feel like they “don’t belong.”

Proponents of middle-child syndrome also believe that middle children often have quiet or dulled-down personalities, compared to their older and younger siblings. Since they fall somewhere in between their siblings, they are less likely to feel special or even equal to them. Adler stated that middle children always feel inadequate, since they constantly try to measure up to the accomplishments of their older sibling. As they struggle to compete with others, they may attempt to carve out a separate niche for themselves so they can stand out.

Studies show that middle children report feeling less family-oriented and less likely to turn to their parents in crises.

At the same time, researchers find that middle children develop many positive characteristics because of their in-between status. These children are likely to become peacemakers and empathetic communicators. They are usually very agreeable, sociable, and loyal to their friends and partners. Studies find that middle children are least likely to act out or rebel. They relate well both to older and younger people alike. Adler himself, who was second in a family of seven children, stated that middle children were the most emotionally stable.

Validity of Middle-Child Syndrome

If you’re a middle child or have a middle child in your family, you might wonder whether this syndrome actually exists.

Research has an answer:

In a nutshell, not really.

According to the American Psychological Association (APA), middle-child syndrome is a “hypothetical condition.” Other research on the validity of the syndrome concludes there’s a lack of supportive and reliable evidence proving the psychological impact of birth order. That’s because so many confounding variables may also contribute to the correlations mentioned above.

For example, larger family size can affect income and educational attainment. That means that from the onset, families with three children (i.e. those that have a middle child) are in a different demographic than those with just one or two.

Many researchers who study the validity of birth order theories draw the same conclusion: it doesn’t exist. There may be one exception, though: the correlation between earlier-born children and intelligence. Reliable evidence shows that firstborns score slightly higher on IQ tests than children born later. However, other theories connecting birth order to personality (or other factors) have too many confounding variables to be statistically reliable.

This means that – whether you’re a middle child and agree with the characteristics that birth-order researchers attribute to your status or not – the current scientific consensus is that middle-child syndrome is more pop psychology than anything else.