I am obsessed by birth order and when Frank Sulloway published his groundbreaking work Born to Rebel: Birth Order, Family Dynamics, and Creative Lives in 1996, I was on the phone from Australia, desperate to do an interview. He was everything I expected: a thorough, disciplined researcher and, of course, a middle child. He'd uncovered a startling finding as he was analysing the lives of scientists who made revolutionary discoveries, or had revolutionary theories. He discovered that those scientists - and those who supported the discoveries - were younger siblings. In other words, we resist. And today, we need more of that than ever before.

There was glee in Sulloway's voice when I asked him about whether he could be sure about the link between those discoveries and the birth order of the scientist. "It was a whopping effect," he said.

The Sulloway thesis is this: the first-born child gets a lot of attention from his or her parents from day one. The parents dote on the baby, who in turn identifies madly with mum and dad. It is a cosy and fulfilling relationship until No. 2 comes along. Now, No. 1 gets the most attention by pleasing the parents and doing as told. No, 2 has to think of a different way of increasing parental investment. No. 2 doesn't need to be the good kid - and also is not likely to get all that unalloyed, undistracted attention.

As a middle born I would argue that all that attention is bad for you! While the growth in single-child families is applauded for a range of reasons, such as environmental impact and financial responsibility, there is one important reason we should have more than one child. Middle children are better people.

I write this after discovering that August 11 is Middle Child Day in the US, a festival of which I had never heard until I read Adam Sternbergh's compelling account of why we need more middle children at the very time we are losing them. He writes: "Middle children, the most populous birth-order demographic throughout most of human history, will soon be the tiniest."

Liz Allen, demographer at the Australian National University and one of the ABC's top five humanities researchers, tells me that big families are declining in Australia, and she predicts could soon be overtaken by families with just one child. She's also got pretty strong views on birth order herself (she's one of seven and has six children of her own). She's a good negotiator and so are her own middle children.

Being a middle child was perfect for me. Forming shifting alliances, teaching my siblings to negotiate with each other, negotiating with my parents on behalf of them. All these patterns of relationships survived the death of both my parents, neither of whom was a middle child. They didn't really understand that they were just perpetuating behaviours which even make it into the academic literature. Sulloway was not the first birth order researcher (that might have been Alfred Adler in 1911) and he's certainly not the last because he has mentored an entire generation of birth order researchers, including Catherine Salmon, the author of the 2011 book, The Secret Power of Middle Children: How Middleborns Can Harness Their Unexpected and Remarkable Abilities. She is not a middle born.

But quite lovely, nonetheless. After the success of her book, she continued researching people like me, to discover that we have more empathy, more independence, more resilience, we are more altruistic. We even have longer relationships. Which, of course, is because our parents are besotted with their brilliant eldest children so we have to learn to deal.

Salmon is also worried that middle borns will die out, which is why, in my view, it's ok to ask people who have one child when they plan to have their next. It's about making sure we have a community with different personal aspects and include those who are, as Salmon calls them, more prosocial.

"Having more children means being less of a helicopter parent to any one child, it puts too much expectation to have just one egg in one basket and some are really damaged by that. Those expectations [on only children] can be crushing."

Salmon is a professor at the University of Redland in California and has some experience in the classroom. She says first borns expect they will be given a certain amount of attention, they are used to being the focus, to privilege. They like to argue about grades.

"A little bit of neglect is a good thing, you become more independent and that is a good thing."

She's also worried that a society of first borns would play too safe, be too risk-averse, won't innovate.

Maybe I'm with Peter Costello on this, the former treasurer of Australia who developed the baby bonus. Have one for mum, one for dad and one for a decent society.

Jenna Price is a Fairfax columnist and an academic at the University of Technology Sydney.