By Sharon Begley, New Zealand Herald
By the ripe old age of eight weeks, your baby should smile (and not because of wind). By five months, she should hug and by six months, play peekaboo - and if she's not, you should tell your paediatrician.
So say reputable paediatricians, as well as parenting websites, magazines and books that your worried mother-in-law so kindly presses on you.
It's hard to tell whether this uptight approach to raising children has caused or just tapped into widespread neurosis, but somehow we've managed to turn some early warning signs into truly dire harbingers: sure indications that a child faces a future of delinquency, stupidity, impulsivity, aggression or other horrors.
This might have made a little (though very little) sense when child-development experts believed, with William Wordsworth, that "the child is father of the man".
For decades, researchers did think that personality is established in childhood, with the ability to form loving relationships, to learn and to feel a sense of well-being.
But a new understanding of how malleable people really are, and of the huge individual variation in development, gives the lie to that belief. Now two studies go further, casting doubt on how reliable early warning signs really are.
The conventional wisdom among parents, policymakers and (to a lesser extent) psychologists holds that early sex - at, say, 14 - makes a teenager more likely to have academic problems, commit crimes, drink, smoke and suffer emotional problems compared with peers who wait until 17 or later (16 is the national average in the United States).
To test this, psychologists at the University of Virginia examined data on 534 same-sex twin pairs in which one twin had his or her first sexual experience an average of two years before the other.
But as Paige Harden and colleagues report in the online edition of the Journal of Youth and Adolescence, they found something unexpected.
"Twins who had sex earlier had lower levels of delinquency and anti-social behaviour a few years later, not more."
Why the discrepancy from earlier studies? Previous research compared unrelated teens who differed not only in when they lost their virginity but in many other ways - most important, genetically.
It therefore could not rule out the possibility that early sex is a result of innate tendencies, such as impulsivity, and that those tendencies can also lead to delinquency.
In other words, early sex does not cause delinquency; a third factor, at least partly genetic, leads to both.
If so, then parents shouldn't see their child's sexual activity as a portent of doom.
Nor should they take the involvement of genetics as meaning that promiscuity is wired into the DNA: identical twins, with identical DNA, differed in when they had their first sexual experience by as much as 14 years.
Different friends and experiences influence when a teen falls off the abstinence wagon, but doing so at a tender age need not spell disaster.
Neither do social and emotional difficulties in very young children.
Preschoolers who are aggressive or disruptive or who can't make friends are thought to be in academic peril, largely because "emotional intelligence" predicts cognitive development so well.
But a study in Developmental Psychology, analysing data from almost 36 000 preschoolers, concludes that those problems have little to do with later school success. Being able to pay attention, and knowing such rudimentary maths as what numbers mean and how to count, matter much more.
Two salient caveats belong here. If social and emotional problems impair a child's ability to pay attention, all bets are off: academics will suffer.
And while those problems do not doom a child to scholastic purgatory, says Roger Weissberg of the University of Illinois, about 200 studies find that teaching children to manage their emotions and cultivate social skills boosts academic performance.
Perhaps the most debated warning sign is attention deficit, especially since critics say that society is "medicalising" normal fidgeting.
To see how different ADHD brains are, researchers at the National Institute of Mental Health scanned the brains of 466 children with or without ADHD, and found that those with ADHD are not "a complete deviation from the template of typical development", as some studies suggested.
Instead, ADHD brains are just slower to mature: there is about a three-year delay in the maturation of several cortical regions, especially those that control high-level thinking, attention and planning, and suppress inappropriate actions and thoughts.
But despite medical opinion that children will grow out of ADHD, delayed maturation of the brain is not like taking longer to reach your adult height.
"Teens with ADHD still have functional differences in their brain, areas of over- or under-activation," says specialist Philip Shaw. "The effects of the delay are carried forward."
It's not easy to tell if a red flag, be it failing to speak until the age of two or not smiling at eight weeks, is truly cause for concern.
But there is one unquestionably real consequence of thinking of your child as troubled, or slow, or difficult, or uninterested in school: it can subtly shift how you treat him and what you expect of him, turning harbingers into self-fulfilling prophecies.