Thursday, July 09, 2009

Are eldest children really a cut above?

Order of birth is said to influence everything from IQ to personality. But is it a myth or hard scientific fact? The article below is an unusually well-informed exposition of the fact that birth order is of trivial importance

I exhibit, it is alleged, the typical personality characteristics of a first-born: swotty, bossy and stubborn. That is the verdict of my husband, the youngest of three sons and possessed of a laissez-faire attitude to life. In fact, I’ve noticed that most first-borns I know are married to later-borns; can any union between eldest children survive the constant jostling for pole position?

Everyone, it seems, has an opinion on birth order. From the kind of personality you have, to the kind of profession you pursue, there is a popular belief that much of it rests on whether you emerged from your mother’s womb before or after your siblings (or somewhere in between). And you can look to almost any sphere of achievement to prop up the story: George W. Bush, the former American President, was more successful than his younger brother Jeb, a mere State Governor, who was in turn more accomplished than their younger brother Neil, a businessman blamed, along with other directors, for the collapse of a savings and loans company. While Bill Clinton excelled at political conviction, the only conviction boasted by his younger brother Roger was one for cocaine possession.

Parents, too, seem to agree that all siblings are not created equal. Last week, an online survey of nearly 10,000 mothers for found that 35 per cent thought their first-born would fare best academically, compared with 15 per cent who named their youngest as the scholar in the family.

But what about the science of birth order? Despite its seductive appeal as an explanation of why children born to the same parents and raised in the same environment can be so different, many researchers believe that birth order has virtually no bearing on personality and behaviour. While there are well-documented differences in, say, IQ between older and younger siblings, those differences are so small as to be negligible, and do not explain differences in temperament.

Ginger Moore, the Professor of Psychology at Pennysylvania State University, who has reviewed the literature as part of her research into child development, says: “There are no clear systematic differences that are a function of birth order and there is no scientific research that shows that there are.” There are simply too many other variables involved in sculpting personality and behaviour, she says, that combine to swamp any minor influence that birth order might exert. While mums and dads might ladle out differing amounts of attention to the various members of their brood, she insists that those discrepancies cannot be boiled down to the single factor of order. It is the most demanding child, not necessarily the eldest, that often monopolises mother.

Professor Moore explains: “There is no doubt that parents treat children differently, and some of that difference may be related to birth order. For example, they tend to be more anxious with first-borns, and some of our research has found that mothers are more positive when interacting with their second child. “However, the way that parents interact with their children, the expectations they have of them and the opportunities they give them, most likely have less to do with birth order and more to do with many other factors, such as the child’s personality, gender, the number of children in the family, the spacing between siblings and parental age.”

Even though the first-born has the undivided attention of her parents, she will be shoved out of the limelight once No 2 arrives. And those later siblings, Professor Moore suggests, bask in the attention of not just their more experienced parents but also of their older siblings. In effect, the younger siblings receive ├╝ber-parenting.

Such a verdict might raise a cheer among later-borns, many of whom feel condemned to live their lives in the shadow of the eldest. But birth order is one of those theories that never quite goes away, lurking quietly in the annals of popular culture until a study comes along that either contradicts or confirms it. A bias towards publishing attention-grabbing papers means that confirmation studies are more likely to make it into print and be noticed by the media. That perpetuates the idea that the birth order view of personality — the dominant eldest, the wayward middle one and the spoilt youngest — is on unshakeable ground.

In addition, the idea of the favoured first-born slots into the Darwinian theory that siblings, whether chicks in a nest or gurgling human beings, must compete against each other for parental attention. Since, in this bleak Darwinian worldview, parents allocate the most resources to the child(ren) most likely to survive and reproduce, lavishing attention on the eldest is a wise strategy.

For well over a century, scientists have toyed with the idea that the road to greatness is littered with first-borns. Francis Galton, the gifted biologist and now notorious eugenicist, noted in 1874 that an unusually high proportion of eminent men (mostly scientists) were first-born sons (women didn’t count, so even if a male had five older sisters, he was still classified as a first-born). Other studies, too, have found first-borns monopolising positions of power and influence, for example, in the higher echelons of medicine and politics.

Galton offered three explanations: that first-borns are treated as mini-adults by their parents and thus invested with more responsibility than future siblings (an echo of the finding); that primogeniture means that the eldest sons inherit the family cash and can therefore bag an education denied to younger siblings; and that eldest children have the best access to food and other parental resources, such as time.

Remarkably, a 2008 study bears Galton out. Dr David Lawson and Professor Ruth Mace, from University College London, discovered that on average, only children are taller than peers from large families. Moreover, the eldest children in those families tend to be taller by the age of ten than younger siblings. Since height is a proxy for nutrition in the well-nourished West, this implies that there is more food on the table for the eldest. The study does not support a birth-order theory of personality — it did not look for such evidence — but it is striking in its support for the Darwinian idea of children competing for parental succour. What about IQ? There is a characteristic IQ distribution among siblings, with first-borns hogging the top of the sibling bell curve, and second and third-borns lagging one , two or sometimes three points behind (the lower your ordinal position, which is your place in the sibling line-up, the lower the IQ).

Robert Zajonc, the late Stanford University psychologist, argued, like Galton did, that this was because firstborns are plunged into an intellectually demanding, adult-only environment. Even sexuality appears to be influenced by birth order: the more older brothers a man has, the more likely he is to be gay (the finding applies only to men). This is known as the fraternal birth order effect, and is a pretty sturdy finding. Since sexuality is influenced by hormones, could it be that the womb environment changes for each sibling, and that this is the key to perceived differences? If so, then those differences should be biologically preset and remain unaffected by how the child grows up. In other words, if you are a second sibling, you will always carry the lower IQ of a second sibling.

However, a 2007 study of 250,000 Norwegian conscripts contradicted this: second siblings who had lost an older brother, and were thus elevated in the family’s social ranking to the status of eldest child, boasted IQs that were more similar to eldest children. Similarly, third-borns who lost their elder sibling had an IQ of a “natural” second-born. This implies that the social environment in which a child is raised has a greater sway over IQ than biological order. Similarly, sexuality researchers tried, and failed, to correlate personality characteristics with fraternal birth order. In conclusion, while the link between IQ and birth order is robust, it is a) too small to affect a person’s life chances substantially and b) actually related to social, rather that biological, rank.

One of the most influential works to claim that birth order moulds personality, was Born to Rebel, by Frank Sulloway. The 1996 best-seller argued that first-borns, keen to preserve their favoured status in the family, stick close to their parents, maintain the status quo and don’t question authority. Consequently, it is later-borns who bloom into the risk-taking, creative individuals capable of changing the world. Sulloway, a University of California psychologist and second-born, marshalled such scientific revolutionaries as Darwin and Copernicus, both later-borns, to bolster his case (interestingly, Tony Blair, Gordon Brown and David Cameron are all younger children).

Although Born to Rebel was heralded as a magisterial analysis of the birth-order literature, many researchers have contested Sulloway’s reading of the data. One of his sternest critics is the psychologist Judith Rich Harris, author of The Nurture Assumption, the landmark book that claimed peers are more important than parents in child development. Rich Harris argues that the supposed birth order pattern in personality — the conventional eldest, the laid-back youngest — only exists when siblings are with each other, and that this pattern disappears outside the family environment. The intellectual battle over the book’s central idea has been long and brutal: Sulloway initially threatened to sue his critics, although an extensive, unflattering critique did finally appear in 2004. [Sulloway acted totally outside normal scientific procedure, making his work of no credibility whatever. More details of that here]

So what now for the science of birth order? While studies of large families might provide the best test-bed for theories, they are, in some respects, the worst. That’s because larger families tend to be poorer; and poverty is linked to lower IQs. Bigger families also mean more complicated family dynamics. And because most studies can’t airbrush out all the other factors that might influence personality, behaviour and achievement, it can be dangerous to take a small positive result — such as the matter of an IQ point here and there — and hold it up as proof that who you are and how you behave depends on whether you are the royal or the runt of the litter.

The theory’s refusal to go away, Professor Moore suggests, might be due to birth order being easily measurable. We all know where we stand in the familial order of things; our rank among siblings is perhaps the one indisputable fact among a host of messy, hard-to-measure factors that cloud or complement our development from child to adult. It’s tempting to hold that one measurable fact responsible for our fates.

But how we eventually turn out, she says, is down to the complex interplay between biology and genes, parenting, social milieu, education, peers, and pure luck of the draw. “A single factor, such as birth order, may explain a small portion of the variability in the paths that children take within families, but trying to predict adult personality or behaviour on the basis of birth order is too simplistic.”


Travel is bad for you! It more than doubles your risk of blood clots

But is it as dangerous as driving your car or crossing the road? I have no doubt that there is something in this but it seems to be very rare in absolute terms

A study published Monday strengthens the evidence that long-distance travel can lead to potentially fatal blood clots in some people -- showing that the risk grows in tandem with the length of the trip. In an analysis of 14 previous studies, researchers found that, in general, travel was associated with a nearly three-fold increase in the risk of venous thromboembolism (VTE) -- blood clots that form in the veins, often in the legs. If such a clot dislodges and travels to the lungs, it can cause a potentially fatal condition called pulmonary embolism.

Several high-profile deaths have brought attention to the risk of VTE among travelers, particularly those on long-haul flights. Experts think a combination of factors -- including dehydration and hours of sitting in cramped conditions -- explains why some people develop blood clots.

However, not all studies have found a clear link between travel and VTE. To look at the discrepancy, the researchers who conducted the current review, published in the Annals of Internal Medicine, analyzed 14 studies involving more than 4,000 cases of VTE. Some of the studies compared VTE patients with a "control" group of people who had been referred for possible VTE symptoms, but were found to not have a clot -- a comparison that carries the risk of bias because the control group likely has a higher-than-average risk of blood clots.

In other studies, the control group consisted of healthy people from the general population -- which are more likely to capture the true VTE risk associated with travel, explained lead researcher Dr. Divay Chandra of the Harvard School of Public Health in Boston. When the researchers looked only at those studies, they found that travelers had a nearly three-fold higher risk of blood clots than non-travelers. What's more, the risk climbed along with the duration of the trip -- rising 18 percent for every two hours of any type of travel, and by 26 percent for every two hours of air travel.

But while the current findings confirm the travel-VTE link, Chandra told Reuters Health, "there is no reason for panic" because the absolute risk to any one traveler is still low. Still, Chandra said, "people who travel long distances should be aware of the risk of blood clots and learn to recognize the symptoms." Symptoms of a blood clot in the leg include pain, warmth, swelling and redness in the limb. If the clot travels to the lungs, it may cause sudden shortness of breath, chest pain or a cough that produces blood.

To help reduce the risk of VTE, experts generally recommend that long-distance travelers periodically move around and stretch their legs, and drink plenty of water to stay hydrated.

Certain people are at increased risk of blood clots, Chandra noted -- including cancer patients, people who have recently had major surgery such as a joint replacement, and women on birth control pills. They may want to talk with their doctors about any precautions they should take when traveling, he said.


No comments: