Birth order and behaviour: A worksheet to support the 6 Concepts

---

This post is about a Worksheet (below) that teachers can use in the first week or two of the course to introduce students to the 6 big Concepts of the course and to allow a conversation about the significance of good research. The worksheet includes a very recent article from BBC News (June 20th, 2025) and a collection of activities for students to complete, perhaps in small groups, perhaps individually, perhaps for homework…

The birth order theory

The birth order theory suggests that your position in the family (firstborn, middle child, youngest, or only child) shapes your personality in predictable ways:

• Firstborns are said to be more responsible and achievement-focused.
• Middle children are often described as peacemakers or attention-seekers.
• Youngest siblings are thought to be fun-loving and rebellious.
• Only children are sometimes stereotyped as selfish or overly mature.

These ideas are fun to talk about at dinner tables — and even show up in TV shows and social media memes — but do they hold up to scientific scrutiny?

---

The research says… no.

Decades of research have tried to pin down whether birth order really causes differences in personality. While some studies have found small patterns — for example, that firstborns might score slightly higher on intelligence tests — larger and better-designed studies have found no consistent, universal effects of birth order on broad personality traits.

That doesn’t mean birth order has zero impact. It may shape behaviour in specific family contexts or cultures, and people’s beliefs about birth order can shape their identities. But overall, there’s very little evidence to say that your position in the family determines your personality in any reliable or scientific way.

This example gives us a good way to start understanding the six key Concepts of IBDP Psychology:

1. Bias

We tend to notice evidence that confirms our expectations and ignore what doesn’t — a classic example of confirmation bias. If your older sister is bossy, you might say “Well, obviously, she’s the eldest.” But what about all the bossy youngest children?

2. Causality

Is it really birth order that causes certain traits? Or could it be age, parenting style, socioeconomic status, or even gender expectations? Psychology often grapples with correlation vs. causation, and birth order is a great example of that complexity.

3. Measurement

How do we measure personality? Many studies rely on self-report questionnaires, which come with limitations. People might describe themselves based on how they think they’re supposed to behave as an oldest child, not how they actually behave.

4. Perspective

The impact of birth order may differ between cultures and families. In some societies, firstborns may carry traditional responsibilities, while in others, birth order is far less significant. Perspective reminds us that psychology is not one-size-fits-all.

5. Change

Your personality and family roles can shift over time. A younger sibling might become more responsible later in life. Psychology recognises that behaviour and identity are not fixed, but dynamic.

6. Responsibility/Ethics

If we assume someone’s behaviour is fixed by their birth order, that can be limiting — even harmful. Ethical psychology considers the social consequences of labelling, stereotyping, and drawing broad conclusions from incomplete evidence.

---

In the first week of IB Psychology, we’ll use this birth order debate to practice:

• Asking critical questions about theories and research
• Exploring the six Concepts in real-world contexts
• Discussing beliefs vs. evidence, and developing a scientific mindset

You’ll be using the attached worksheet to guide your thinking and conversation. Don’t worry — you don’t need to be an expert in Psychology yet. The goal is to start asking smart questions and learning how to evaluate claims, whether they’re in a textbook, a TikTok post, or a family argument at dinner.

---

Final Thought

---

1. What is your birth order?
   (First-born, middle child, youngest, only child, twin, etc.)
2. Do you think your birth order has influenced your personality or behaviour?
   If so, in what ways?
3. Do people ever describe you using “birth order” traits?
   (e.g. “You’re such a responsible oldest child” or “Typical youngest!”)
   Do you agree or disagree with those descriptions?
4. How are your siblings’ personalities different from yours?
   Do you think these differences are because of birth order, or something else?
5. Do you think all first-borns are more responsible? All youngest siblings more fun or rebellious?
   Why or why not?
6. Do you think people act a certain way because of their birth order — or because they believe birth order affects their behaviour?
   Can belief shape personality?
7. Do cultural or family expectations influence how children behave based on their birth order?
   Can you think of an example?
8. Have you ever changed your role in the family over time?
   For example, were you once the “quiet one” but became more assertive? What caused that change?
9. Do you think only children are different from children with siblings?
   In what ways, and why?
10. If someone knew nothing else about you except your birth order, what might they assume about your personality?
    Do you think they’d be right?

---

These questions can lead to some rich and open discussion — and they provide a natural bridge into critical thinking, the importance of evidence-based research, and the limitations of generalisations in psychology.

Final thought…

Psychology is full of ideas that sound right — but part of becoming a psychologist is learning to dig deeper. The birth order theory may not be strongly supported by data, but it gives us the perfect launchpad into the skills, attitudes, and concepts that define this course.

---