Why firstborn kids are smarter.

Why firstborn kids are smarter.

Why firstborn kids are smarter.

Science, technology, and life.
June 22 2007 10:42 AM

Dumb and Dumber

Why firstborn kids are smarter.

(For discussions of the latest topics, check out the new  Human Nature Fray.)

Sand holes kill more people than sharks do, according to two doctors. Since 1985, the unsystematically collected data show 20 deaths from "beach or backyard sand submersions" in the United States, and eight more in the United Kingdom, Australia, and New Zealand. From 1990 to 2006, U.S. data show 12 fatal shark attacks compared to 16 deaths from sand holes or tunnels. The doctors suspect the real numbers are worse, since sand-hole deaths are less likely to be documented than shark attacks. Cause of death: "Typically, victims became completely submerged in the sand when the walls of the hole unexpectedly collapsed, leaving virtually no evidence of the hole or location of the victim." Old warning: Don't go into the water. New warning: Don't come out. (For shark attacks vs. lion attacks, click here. For sharks that eat each other in the womb, click here. For a critique of shark lovers, click here.)

William Saletan William Saletan

Will Saletan writes about politics, science, technology, and other stuff for Slate. He’s the author of Bearing Right.


Eldest children have IQs three points higher than their siblings, on average, in a huge sample of young Norwegian men. The study shows this difference is due to family dynamics, not "prenatal gestational factors," since "second- and third-born men who became the eldest in their families due to the death of one or two older siblings … had IQs close to that of firstborns." Theories: 1) Firstborns get more parental attention. 2) They're presented with higher expectations. 3) They benefit from teaching younger siblings. 4) They strive to achieve, so their siblings seek a less achievement-oriented identity. Critiques: 1) The difference is just an average; when sibling IQ scores differ, there's a 43 percent chance the younger kid scores higher. 2) Smaller U.S. studies differ from the Norwegian one. 3) Previously asserted birth-order effects have been debunked. 4) Younger siblings are less likely to be smart but more likely to be brilliant. 5) Younger siblings may have lower IQs, but they're more interesting. (To debate IQ and birth order, click here.)

President Bush vetoed another bill to fund embryonic stem-cell research. He faulted the research for relying on embryo destruction, and he issued an executive order encouraging alternative, nondestructive methods of making stem cells. White House spin: Forget "embryonic" stem cells—let's promote "pluripotent" stem cells. Critiques: 1) The order delivers no new funds for alternative research. 2) The alternative methods might take years to become practical. Rebuttal: The same is true of embryo-destructive stem-cell research. Bonus report: Sixty percent of couples who have frozen their IVF embryos say they'd donate them for stem-cell research, which "could result in roughly 2,000 to 3,000 new embryonic stem-cell lines." Bush's policy would bar federally funded research on these cell lines. (To debate stem-cell research, click here.)

An eye-tracking study suggests women are more likely than men to look at genitals in sexually explicit photos. The study of 45 heterosexuals aged 23 to 28 tested 15 men, 15 "normal cycling" women, and 15 women on birth-control pills. Results: 1) "Men spent more time, and had a higher probability of, looking at female faces." 2) Normal cycling women "had more first looks towards, spent more time, and had a higher probability of, looking at genitals." 3) Women on pills "spent more time, and had a higher probability of, looking at contextual regions of pictures, those featuring clothing or background." Researchers' theory: The difference is biologically driven, since "women can tell by looking at naked men whether the guys are in the mood," but men have to look for cues in a woman's face. (For a contrary eye-tracking study that caught men staring at a crotch, click here. To discuss sex differences in erotic psychology, click here.)

Companies are recruiting and interviewing prospective employees in Second Life. Their digital avatars talk with the applicant's avatar through IM. Microsoft, Verizon, and Hewlett-Packard just participated in a job fair this way. Rationales: 1) It's cheaper than putting recruiters on planes. 2) It makes your company look hip and creative. 3) Your executives can participate from wherever they're traveling. 4) You get more thoughtful answers from applicants by letting them think and type. 5) It's more natural than a real conversation, since tech-oriented young people chat online more than offline. Problems: 1) It can take more work to prep your avatar than it would to prep yourself. 2) There's no eye contact to help you gauge how you're coming across. 3) Avatars have accidentally floated during interviews, slumped over as though asleep, and handed an employer a beer instead of a resume. (WSJ link requires subscription.) (For previous updates on virtual sex, crime, commerce, terrorism, and religion, click here, here, here, here, here, and here. For Human Nature's take on policing cybersex, click here.)


Activists are fighting over whether to bar demented people from voting. Trends: 1) Thanks to improved longevity, more and more people are demented. 2) Campaigns are pushing harder to get out the vote, even if you're a bit senile. 3) Advocates for the mentally disabled are trying to expand their voting rights, while critics are trying to stop them. Examples: Elections in several states have been marred by charges that nursing home residents shouldn't have voted; some mental-hospital patients vote despite having escaped murder convictions by being declared insane. Arguments against these people: 1) "If you are declared insane you should not be allowed to vote." 2) Demented people are too easily manipulated. Defenses: 1) Don't discriminate against the "disabled." 2) You can be sane enough to form political intent even if you're not sane enough to form criminal intent. 3) Voting is "part of their treatment, to try to move them closer to society." 4) Your neighbor still gets to vote even though he's dumber than somebody with a diagnosed defect. (To debate the voting rights of old people, click here.)

Gestating with a male twin makes a girl 25 percent less likely to become a mother than if her twin is female, according to a Finnish study. Women whose twins were male were 15 percent less likely to marry; those who became parents had two fewer children. Researchers' theory: Testosterone poisoning. Explanatory speculations: 1) "Perhaps the female twins had more masculine attitudes and behaviors that affected their decision to get married." 2) "Male features could have made the women less attractive to mates." 3) "Exposure to elevated levels of testosterone during development can promote diseases that compromise fertility, such as reproductive cancers." Bonus finding: Gestating with a female twin had no such effect on boys. Caveat: The study was based on church records from two centuries ago, "to obtain results that are not affected by advanced health care and contraception." (For a previous update on differences between lesbian and heterosexual brains, click here.)

"Ex-gay" activists are beginning to accept homosexuality as innate. Leaders of Exodus International, the leading U.S. ex-gay ministry, now "talk deliberately about a possible biological basis for homosexuality, in part to explain that no one can turn a switch and flip from gay to straight." This matches a new Gallup poll in which 42 percent of U.S. adults say homosexuality is innate. Old idea: Faith frees you from homosexuality. New idea: You still have gay inclinations, and you accept them, but you can manage them to seek harmony with your religious beliefs. Excited liberal view: Antigay leaders are becoming ex-antigays! Skeptical view: They're just trying to manage their antigay inclinations. (For a previous update on conservatives acknowledging homosexuality as innate, click here. For gay sheep and the biology of homosexuality, click here and here. For the pope's doctrine on struggling with homosexuality, click here. To debate homosexuality, click here.)

Britain's Academy of Medical Sciences endorsed the creation of "human embryos containing animal material" for research. Reasons: 1) It'll help us study diseases, cure children, and test drugs. 2) Putting human DNA in animal eggs will "spare the use of valuable human eggs." 3) It presents "no significant safety risks over and above regular cell culture research." Academy's caveats: 1) Don't implant the hybrid embryos in a woman or an animal. 2) Don't let them grow beyond 14 days. Bonus declaration: "We found no current scientific reasons to generate 'true' hybrid embryos by mixing human and animal gametes. However, given the speed of this field of research, the working group could not rule out the emergence of scientifically valid reasons in the future." (For Human Nature's take on growing embryos beyond 14 days to harvest their organs, click here. For virgin births and human-animal hybrids, click here. To post your views on hybrids, click here.)

Tattoos are getting easier to remove. Estimates: Up to 45 million Americans are tattooed; 17 percent of them regret it; the annual number of tattoo removal treatments might be 100,000. Summary by a removal company's CEO: "As your life changes from young to middle-aged to older, from single to married to divorced, you get tattoo regret." Sample reasons: 1) Get my ex-fiance's name off my body. 2) I don't want my tattoos to show around my strapless wedding gown. 3) I need to start looking employable and marriageable. 4) I want to replace my old tattoos with new ones. Current removal technology: multiple expensive laser treatments to break down each color. Impending technology: special ink that can be removed with a single laser treatment. CEO's pitch: The new ink will embolden "fence-sitters who always wanted a tattoo but have been afraid of the permanence." Half-cynical view: It'll make them feel as though they're getting a real tattoo when, in fact, they aren't. Fully cynical view: Removable tattoos for the era of removable relationships. (To debate tattooing in the Fray, click here.)

Latest Human Nature columns: 1) The spread of virgin births. 2) The abolition of menstruation. 3) The chess match of man and machine. 4)  Ultrasound and the future of abortion. 5) The global market in human organs. 6) The evolution of brains and morals. 7) Machines that read your mind. 8) Invasion of the naked body scanners. 9) The future of pain-beaming weapons.

* Correction, June 14, 2007: The item on captchas (Completely Automated Public Turing Test to Tell Computers and Humans Apart) originally said that test images had become so hard to decipher that a company's chief technology officer flunked 75 percent of them. The source article actually said that the CTO passed 75 percent of the tests, which were administered by Ticketmaster. For this mistranslation, Human Nature blames … human error. Return to the corrrected sentence.