Exploring “Birth Order Theory” & Attachment Styles

Birth order theory and attachment theory are linked in that they can influence our personalities and how we think and act in relationships. This article explores the connection between both phenomena and how they can impact our development across the lifespan.

Have you ever felt like your siblings have a different relationship with your caregivers than you? While your parents may shrug this off as untrue, there may be some accuracy to it, and these differences could be partially due to your birth order.

Birth order is a person’s rank among their siblings in order of age. According to birth order theory, our birth order can significantly affect many aspects of life, including the attachment style we develop and our thoughts and behaviors in later relationships.

To answer all of your questions on birth order theory and attachment styles, this article will cover what birth order theory is and the influence of birth order theory on attachment.

What Is Birth Order Theory?

Birth order theory is the idea that the order in which we’re born plays a significant role in shaping our personality as children. This idea was first developed by researcher Alfred Adler in the 20th century. However, since then, many psychologists have studied the phenomenon and claim that birth order can also influence the attachment style we develop and how we think and behave in later relationships.

How Might Birth Order Influence Personality?

When birth order theory was first developed, Adler claimed that firstborns were “power-hungry,” the middle child stereotype was that they were highly competitive, and lastborns were lazy and spoiled. However, you’ll be pleased to know that much has changed as we’ve learned more about the effects birth order has on us.

Recent research into birth order theory appears to show that firstborns tend to be more conscientious than their siblings. Their conscientiousness is often a combination of ambitiousness, responsibility, organization, and academic success. Firstborns also tend to be more extroverted in a dominant and assertive way and often score higher on neuroticism—the personality trait associated with anxiety, irritability, and self-doubt. While this could be due to a number of environmental factors relating to being a firstborn, experts suggest that this personality difference may be due to their anxiety around their status in the family.

Laterborns also often show extroversion, but in a more friendly and fun-loving way. Youngest child traits also include being generally more agreeable than firstborns, too—they tend to be more selfless, compassionate, and eager to please. Furthermore, they’re typically more open to new experiences, so they may be more adventurous and unconventional, frequently engaging in more risk-taking activities like extreme sports.

Influence of Birth Order on Attachment Styles

Adler proposed that the caregiver-child relationship and the care and protection the caregiver provides are dependent on birth order. So, based on this, it’s likely that birth order plays a role in the attachment style we develop. However, it’s important to note that our attachment bonds are multifaceted. Birth order is by no means the only influential factor—instead, it’s one of many.

So, let’s take a look at the pattern for firstborns, middle children, and lastborns, as well as only children, and how their birth order influences their attachment style.

Firstborns & Stereotypes

Birth order personality traits are not “set in stone” – such children are not born with particular personality traits ingrained into their persona. Nevertheless, there are some stereotypes around firstborn personality traits. For example, Adler believed that firstborn children are influenced by their caregivers to be more responsible and ambitious. Other firstborn stereotypes include being more independent, assertive, and responsible. Furthermore, people believe that firstborns attempt to impress their parents by being more conscientious and acting as caretakers to younger children.

Firstborn Traits

Studies concerning birth order theory suggest that there are a number of factors outside of familal which contribute to certain personality traits in firstborn children. These factors include:

• Biological
• Social
• Cultural
• Physical environment
• And situational factors

Regardless, there are still certain personality traits associated with firstborns according to birth order theory. These personality traits include:

• Dependability and reliability
• High achievement and leadership
• Feelings of superiority
• Feelings of rejection when a second child is born
• Authoritarian behaviors around rules and regulations
• People-pleasing actions
• Attention-seeking behaviors to capture caregivers’ attention

However, bear in mind that these are traits in general, and that other factors outside of the family environment can go a long way towards shaping a child’s personality.

Firstborns & Attachment Styles

Firstborn children have their caregivers’ undivided attention until their first sibling comes along. Our first two years of life are fundamental in forming our attachment style: So, if a firstborn child had their caregivers’ undivided attention for the first two years of their life, they may be more likely to develop a secure attachment style.

However, this isn’t always the case. For example, it’s normal for caregivers to have new-parent nerves when caring for their first child. As the experience is novel and unknown, caregivers are often uneasy, worried, or over-protective, sometimes resulting in a stricter or more anxiety-led parenting style. Firstborns may be less self-sufficient and independent as a result and might develop an insecure attachment style.

Furthermore, a firstborn’s “dethronement” (as many experts call it) when their first sibling is born may cause an attachment rupture, potentially leading to an insecure attachment style.

YouGov—a global public opinion and data company—conducted a survey on birth order in 2023 and found that 32% of firstborns considered themselves securely attached, whereas 16% of them said they had a disorganized attachment. 20% identified as avoidantly attached, and 18% as anxiously attached.

However, we need to take these findings with a pinch of salt. As this survey was based on self-reported data, it may not be 100% accurate, as, sometimes, self-reporting can be prone to bias. Nevertheless, these general trends can help us build an understanding of how birth order may influence our attachment styles.

If you’re unsure of your attachment style and want help identifying it, check out our free Attachment Style Quiz.

Middle Children & Stereotypes

As we mentioned for first borns, birth order personality traits are not rigid – children are not born with particular personality traits ingrained into their persona. Nevertheless, there are some stereotypes around middle child personality traits. For example, “middle child syndrome” is a widely known phenomenon whereby people understand that middle children are attention seekers, feel excluded or even neglected, and have low self esteem as a result. However, studies concerning birth order theory suggest that there are a number of factors outside of familal which contribute to certain personality traits in middle children. These factors include:

• Biological
• Social
• Cultural
• Physical environment
• And situational factors

Regardless, there are still certain personality traits associated with firstborns according to birth order theory. We’ll discuss these next.

Middle Children Traits

According to studies concerning birth order theory and personality traits, middle born children may be prone to characteristics such as:

• High independence
• Competitiveness with other children in the family
• Good social skills with friends and adults
• Risk-taking behaviors
• Feelings of isolation
• Easy going nature so as to not “rock the boat”
• Low self-esteem
• Good sharing abilities
• Peacemaking between family members

Having said as much about these traits of middle children, remember, this is just a guideline based on birth order. The other environmental factors discussed above will influence a child’s development.

Middle Children & Attachment Styles

The middle child tends to be in the most competition for their caregivers’ attention because they have to rival both their older and younger siblings. They aren’t given the undivided attention of the firstborn and aren’t the prime focus of their caregivers’ attention for long, either, as their younger sibling comes along.

This continual competition for attention may cause middle children to feel uncertain about their caregivers’ feelings towards them and their value as a whole, leading to an insecure attachment style. Research also suggests that middle children often feel less invested in their families but tend to turn to friends as important attachment relationships.

The YouGov Survey found that 33% of middle children were securely attached, 20% had a disorganized attachment style, 20% were avoidantly attached, and 18% were anxiously attached.

Lastborns & Stereotypes

Again, the personality traits according to birth order theory and last borns are not inflexible; childrens’ environmental dynamics also influence the traits the develop. However, there are certain stereotypes around the characteristics of last born children, which include acting jovial and clownish, yet also manipulative and charming in attempts to get what they want from family members.

However, studies around the environmental dynamics which influence a child’s personality traits include:

• Biological
• Social
• Cultural
• Physical environment
• And situational factors

Regardless, there are still certain personality traits associated with lastborns according to birth order theory. We’ll discuss these next.

Lastborn Traits

According to studies concerning birth order theory and personality traits, lastborn children may be prone to characteristics such as:

• A fun-loving nature
• Charming and charismatic personality
• Manipulative tendencies
• Extraversion
• Attention seeking actions
• Self-centredness
• Good social skills

Although these traits of lastborn children are in line with birth order theory, it’s still important to be mindful of the environmental factors which contribute to a child’s personality traits.

Lastborns & Attachment Styles

Being the last born has unique benefits—they receive attention from their caregivers and their older siblings. What’s more, as the youngest is the last child caregivers will ever have and are the most vulnerable to illness because they are the smallest (as children, anyway), caregivers tend to offer them more support than middle children. As a result, lastborns tend to have stronger attachments than middle children and feel like a more integral part of the family as they get older.

The YouGov Survey found that 37% of lastborns say they have a secure attachment style. 18% report having a disorganized attachment, 16% an avoidant attachment style, and 16% an anxious attachment style.

Only Children & Stereotypes

The stereotypes of an only child’s personality include those of these children being spoiled, narcissistic, and self-centred in comparison to children with siblings. However, these are out of date stereotypes and the traits of only children according to birth order theory are quite different. We’ll discuss these traits momentarily. First, as a recap, the environmental factors associated with a child’s personality development include:

• Biological
• Social
• Cultural
• Physical environment
• And situational factors

Only Child Traits

The research concerning birth order theory and only children account for the following personality traits:

• Maturity
• Independence
• Curiosity
• Sensitivity
• Leadership
• Cautiousness
• Ambitiousness
• Lack of competitiveness

However, as previously mentioned, these traits don’t account for the environmental factors which we discussed.

Only Children & Attachment Styles

Only children are never “dethroned,” like lastborns. However, they differ from lastborns in that they don’t ever have to compete for their caregivers’ attention, as they have no siblings to compete with.

Yet, despite the lack of sibling rivalry, being an only child still appears to influence attachment style. For example, only children often spend most of their time with adults as they have no one else their age within their direct family unit. As a result, they become “adult-oriented”—they behave in more adult ways and have worries more commonly associated with adults.

Only children also tend to develop higher conversational abilities but less age-appropriate social skills, which means they generally feel more comfortable around adults than people their age. So, while approximately 27% of only children consider themselves securely attached (as per the YouGov Survey), they may struggle to form healthy attachment relationships later in life because of these social difficulties.

Disorganized attachment appears particularly common in only children, with around 25% of only children claiming they have this attachment style. A smaller 20% of only children identify as having an avoidant attachment, and 17% as anxiously attached.

A Small Caveat of Birth Order Theory & Attachment Styles

Before we conclude this article, it’s important to point out that these are the general trends we see based on the current research. Any child, regardless of their birth order, is able to develop a secure attachment style as long as their caregiver attunes to their needs and responds to them with empathy, warmth, and understanding.

Furthermore, our unique childhood experiences influence us in adulthood in different ways. So, for example, you can be a firstborn and still be adventurous, or you can be a lastborn and be highly independent. Your birth order doesn’t define you, but it may make you more likely to encounter certain experiences.

Final Word on Birth Order Theory & Attachment Styles

Birth order theory suggests that we’re more likely to be secure or insecurely attached based on whether we’re born first, sandwiched between two or more siblings, or last. While firstborns get their caregivers’ undivided attention, this may not be for long. When their siblings come along, they’re “dethroned,” which can shake the very foundation of their attachment bonds.

Middle children often pull the short straw as they never get their caregivers’ undivided attention, but they can find solace in the comfort of friendships. Yet, the opposite can be said for lastborns—they tend to develop strong family bonds and receive undivided attention due to being the youngest and, therefore, most vulnerable.

Only children, on the other hand, never face sibling rivalry. However, they face different challenges, developing adult tendencies in childhood, and making relationships harder in later life. Yet, as we previously mentioned, your birth order doesn’t define you–your experiences, personality, and relationships to date help make you the unique person you are.