I finished a book on birth-order yesterday:

The book was fine.

Reading along, I was nodding, agreeing, pulling out examples from my life, relationships, my own family, etc.

I started telling wife about this trait and that behavior in myself, in her, in our sons, etc.

Then, hmmm… it all felt a little too just so.

I realized that this has the smell MBTI.

Like astrology.

We latch onto the bits that fit or sound good, and leave the rest and think it’s real.

Is birth order pseudoscience? My gut says: smells like it.

I’m not alone, this review:

…I don’t know who this book is for. It reads like a book on starsigns….

Ha, astrology. I love it. We both got there :)

From wikipedia:

Birth order refers to the order a child is born in their family;[1] first-born and second-born are examples. Birth order is often believed to have a profound and lasting effect on psychological development

Hmm: “profound and lasting effect”. That is what the book was taken as a given.

Followed by:

…This assertion has been repeatedly challenged. Recent research has consistently found that earlier born children score slightly higher on average on measures of intelligence, but has found zero, or almost zero, robust effect of birth order on personality. Nevertheless, the notion that birth-order significantly influences personality continues to have a strong presence in pop psychology and popular culture.

Nod.

Okay. Should have read wiki before the book.

A chat on perplexity gave me similar, but less strong language.

The concept of birth order influencing life outcomes, such as personality, intelligence, and success, has been a topic of debate for over a century. While some studies suggest small effects, the overall scientific consensus indicates that birth order has minimal to no meaningful impact on broad personality traits or life outcomes.

Lots of papers referenced in our chat.

The problem I have with perplexity is I need a color coding or something on high vs low quality papers/journals/conferences. In my field, I can see this a mile off, but for other fields I have no idea.

It’s measurable (start with impact factor?). Add it!

Our “bro gpt4o” (I love the rhyming of this) had similar idea, per-claim considerations:

The scientific validity of birth order effects on intelligence, personality, success, and other life outcomes is highly debated. It lies in a gray area between science and pseudoscience, depending on the specific claim and the quality of supporting evidence.

It was very helpful.

I asked him to summarize into one bullet point per claim:

  • IQ: Firstborns may have a slightly higher IQ (~1-3 points), but the effect is small and likely due to environmental factors, not biology. (Weak-to-Moderate Science)
  • Personality: No strong evidence that birth order systematically affects personality traits when controlled for other variables. (Weak Science, Near Pseudoscience)
  • Success: Claims that firstborns are more successful (CEOs, astronauts, Nobel laureates, etc.) are largely overstated and confounded by other factors. (Weak Science, Close to Pseudoscience)
  • Education: Firstborns might have slightly higher educational attainment, but the effect is small and often linked to parental investment rather than birth order itself. (Weak-to-Moderate Science)
  • Relationships: No scientific evidence that birth order affects relationship compatibility or social dynamics in a meaningful way. (Pseudoscience)

All weak or pseudoscience.

Nod.

A very cool way to summarize a field, if he’s accurate.

While reading, I liked the metaphor that each child finds a niche in the dynamics of the family.

I like evolutionary biology/ecology metaphors. Who doesn’t!

It too is probably bunk, or at least not (ethically) testable, perhaps not falsifiable.