Here's what we know about only children: they are spoilt and over-indulged; they struggle to make friends, at school or in later life; their education and career suffers from the lack of rough and tumble with siblings; and their parents, of course, are selfish to put them through all this, choosing their own welfare over their child's.
Except, of course, this is all nonsense – myths and half-truths that have somehow become accepted wisdom.
Worse still, these myths are based on a single piece of research carried out over a century ago. What we think we know about only children stems from an 1896 study by US psychologist Granville Stanley Hall: 'Of Peculiar and Exceptional Children.'
Hall popularised the idea that a lack of siblings caused deep and lasting developmental problems – but, as with most 100-year-old research, his ideas have since been disproven.
Take the US study carried out this August, which found that 'onlies' have equally good social skills as kids with brothers or sisters. The study, of 13,000 11- to 18-year-olds, found that although only children had slightly poorer social skills at nursery, by adolescence they had caught up and were just as popular as kids with siblings.
Donna Bobbitt-Zeher, assistant professor of sociology at Ohio State University and co-author of the study, says onlies' social skills develop by hanging out with fellow students and friends: 'Whatever disadvantage only children might have when they start schooling is outgrown as they progress through school and go to scouts and other extracurricular activities,' she says.
There goes the 'lonely onlies' myth.
And, says Bobbitt-Zeher, only children do better in the classroom than those with siblings. 'Generally, children who have more siblings do worse in school and on standardised tests than children with few siblings,' she confirms.
It's still not clear exactly why this is, but common sense suggests that a smaller brood means you have more time, attention and encouragement to lavish on your son or daughter. Of course, no-one's arguing that parents with more children should feel guilty either – just that there are advantages, rather than the oft-assumed disadvantages, to having less kids.
One thing that is clear is the rising tide of parents opting to have less kids. The latest figures show that homes with just one child now make up around half of all UK families. And if the current trend continues, lone-child families will soon be in the majority.
Why? Well, it's hard to look further than our current economic travails.
A report this February revealed that parents are typically shelling out £9,610 a year to feed, clothe and educate each new member of the family. That means the average cost of raising a child to the age of 21 is now £201,809 – and that doesn't include uniforms, sports equipment and school trips, which add a further £52,881.
In a recent UK survey, seven out of ten women polled said they were delaying motherhood because they couldn't afford to have a baby.
Susan Newman, an American social psychologist and author of Parenting an Only Child: The Joys and Challenges of Raising Your One and Only, says cost is just one of a number of factors counting against big families.
'The downturn is affecting child-bearing, but so is the fact that women start families at an older age, leaving little time for another child – and they both need and want to work. There's also an increase in single-parent families and second or third marriages to someone who already has children and will only agree to one more,' she argues.
It looks like small families are the future.
So, says Newman, it's time to stop the only-bashing: 'Only children – and their parents – have been maligned for way too long,' she says, 'but the ideal family of mom, dad and two children is not the way the world is now. Hopefully, as the number of singletons increases, we will see the negatives and nasty comments start to dissipate.'
Dan Roberts is dad to one son and writes The Imperfect Parent column on Parentdish.
For an opposing view, read 'I was an only child - that's why I have four children.'