problems do not appear to arise from any other common factor.
Dick, however, makes a mistake: He confuses a cause-in-population claim with
a general causal claim. He is right that his mother's experience would disprove the
general causal claim, but it has no force against the cause-in-population claim.
Zoe's confusion is that she thinks there is a perfect correlation between
drinking and physical or mental problems in the child, so that if Dick's mother had
not drunk he would have been better, even if Zoe can't point to the particular way in
which Dick would have been better. But the correlation isn't perfect, it's only a
statistical link.
The problem of selection bias in cause-in-population studies:
No matter how carefully studies are made on the effectiveness of different
contraceptives, they will be only marginally useful in helping women choose
which method to use. That's because women who most want to avoid
pregnancy choose the contraceptive they think will be most effective. So the
women using the pill, which is currently touted as the most effective of the
common ways to avoid pregnancy, will be more motivated to follow the
instructions for its use and always use it, while those who use contraceptive
foam are likely to be more lax in following the method. And, according to the
scientists who devise these studies (see the article "Data called misleading in
rating contraceptives," New York Times, December 1, 1987), there doesn't
seem to be any way to correct for this bias in the analysis of the data.
Exercises for Section D
Describe what evidence you have for the claims in Exercises 1-5 and what experiments
you would devise to try to prove or disprove them. (Don't do the experiments yourself!)
1. Universities cause students to become smarter.
2. Hedonistic lifestyles cause premature death.
3. Money brings happiness.
4. Drinking alcohol causes promiscuous behavior.
5. Unprotected sex causes disease.
Explain what's wrong in Exercises 6-9.
6. Tom: Don't feed those chicken bones to Spot. Don't you know that a dog can choke
and die on one of those?
Dick: Don't be silly, I've been giving Spot chicken bones for years.
324 CHAPTER 15 Cause and Effect
7. Suzy: Vegetarians get cancer much less than meat-eaters.
Manuel: Oh, yeah, so how come Linda McCartney, a well-known vegetarian, died
from cancer when she was only in her 50s?
8. Dick: Hey, Zoe. Listen to this. A Roper survey said wine drinkers are more
successful than those who don't drink. Frequent wine drinkers, it says, earn
about $67,000 a year, while occasional drinkers earn about $40,000. Those
who don't drink at all earn a little more than $30,000.
You want to be successful, don't you?
Zoe: You're not going to get me to start drinking wine that way.
9. Maria: Wives of servicemen suffer domestic abuse at the rate of 2 to 5 times that of
other women.
Suzy: Boy, I sure hope Tom doesn't join the army.
10. One of Dr. E's dogs gets loose. He comes back the next day. He's coughing and
hacking, and he vomits a couple times. Dr. E thinks maybe he ate something bad.
Three days later that dog is O.K., but his other dog, who hasn't left the yard, is coughing
and hacking, and vomits. Dr. E concludes that his dogs have had a flu or some illness.
Explain why you think Dr. E is right or why he is wrong.
Analyze the following passages by answering these questions:
What causal claim is at issue!
Which type of cause-in-population experiment, if any, was done!
Evaluate the evidence for the causal claim.
How would you further test the claim!
11. Two new studies back value of high-fiber diet
New research has revived the notion that a high-fiber diet may protect against colon
cancer. Long-standing recommendations for high-fiber diets have taken a hit over the
last few years after a handful of carefully conducted studies failed to find a benefit.
But experts say two major studies published this week in The Lancet medical
journal—one on Americans and the other on Europeans—indicate previous research
may not have examined a broad enough range of fiber consumption or a wide enough
variety of fiber sources to show an effect.
"These two new findings show that the fiber hypothesis is still alive," said the leader
of the American study, Ulrike Peters of the U.S. National Cancer Institute.
Figuring out the relationship between nutrition and disease has proved difficult, but
experts say fiber is particularly complicated because there are various types and they all
could act differently.
Fiber is found in fruits, vegetables and whole grains. Americans eat about 16 grams
a day, while Europeans eat about 22 grams. The new studies indicate fiber intake needs
to be about 30 grams a day to protect against colon cancer.
There are 2 grams of fiber in a slice of whole meal bread. A banana has 3 grams and
an apple has 3.5 grams, the same as a cup of brown rice. Some super-high fiber
breakfast cereals have as much as 14 grams per half cup.
EXERCISES for Section D 325
In the American study, investigators compared the daily fiber intake of 3,600 people
who had precancerous growths in the colon with that of around 34,000 people who did
not. People who ate the most fiber had 27 percent lower risk of precancerous growths
than those who ate the least.
In the European study, the largest one ever conducted on nutrition and cancer,
scientists examined the link in more than 500,000 people in 10 countries.
Those who ate the most fiber, about 35 grams a day, had about a 40 percent lower
risk of colorectal cancer compared with those who ate the least, about 15 grams a day,
the study found.
"In the top quintile (group) they were eating 15 grams of cereal fiber, which is
equivalent to five or six slices of whole meal bread, plus they were eating seven portions
of fruit and vegetables a day, which is basically the Mediterranean levels," said the
study's leader, Sheila Bingham, head of the diet and cancer group at Cambridge
University's human nutrition unit. Associated Press, May 2, 2003
12. [Bernard] Goldberg documents the steady decline in the behavioral, emotional and
physical health of America's kids that has taken place as the percentage of latchkey and
day-care children has increased. Some examples:
• From 1979 to 1988 (a period that coincides with a sizable increase in two-income
families), the suicide rate for girls 10-14 rose 27 percent, while for boys it rose 71
percent.
• In 1970, only one in 20 American girls under 15 had had sex; today, one in three is
having sex, and 3 million teenagers are infected with sexually transmitted diseases every
year.
• A study of 5 million eighth-graders found that children who are left home alone
more than 11 hours a week are three times more likely than kids with after-school adult
supervision to abuse drugs, alcohol or tobacco.
• A study by the National Institute of Child Health and Human Development
published in 2001 found that toddlers in full-time day care tended to be more aggressive
toward other children and defiant
toward adults. This, the institute found, regardless of
the quality.
Goldberg acknowledges that not all the evidence is bad. Some studies on day care
have found it's not bad at all. (When one considers only studies conducted by people or
groups without apparent bias, however—as is the case with the above study—the results
always paint a not-so-pretty picture.) And he's clear that he's talking about parents who
choose to work outside the home, not those who effectively have no choice.
lohn Rosemond, "Parenting," Albuquerque Journal, March 7, 2002
13. Vitamin E in moderation may protect heart
Eating a moderate amount of food rich in vitamin E, such as nuts, vegetable oils and
margarine, reduces the risk of death from heart disease, says a study in today's New
England Journal of Medicine.
This supports a growing body of evidence that links vitamin E to a healthy heart.
Researchers surveyed 34,486 postmenopausal women about their eating habits in
326 CHAPTER 15 Cause and Effect
1986 and followed up about seven years later. They studied women but say the results
apply to men, too.
They found women with the diets highest in vitamin E-rich foods had half the risk
of death from heart disease compared with those eating diets low in these foods. The
highest group got more than 10 IUs of vitamin E from food daily, the equivalent of about
an ounce of almonds. Those in the lowest group got about half that amount.
Margarine and salad dressings are high in fat and calories, so people should use
common sense when eating them. "I wouldn't go overboard with these things, but I
wouldn't necessarily cut them out entirely," says the study's lead author, Lawrence H.
Kushi of the University of Minnesota School of Public Health. The women who did the
best in the research did not eat "outrageous amounts" of vitamin E foods.
Dr. Walter Willett, Harvard School of Public Health, says "one of the unfortunate
parts of the fat phobia is that people eliminate major sources of vitamin E in their diets."
This study didn't come to a definitive conclusion on supplements, but other studies
indicate they are beneficial.
Other rich sources of vitamin E: hazelnuts, sunflower seeds, wheat germ, mayon-
naise, peanut butter, avocados. Nand Hellmich, USA Today, 1996
14. Academy Award winning actors and actresses
(from the transcript for National Public Radio's All Things Considered, May 15, 2001)
ROBERT SIEGEL, host: An article reached us today with the title Survival in Academy
Award-winning Actors and Actresses. It is not about casting or contracts. It's actually
in the Annal of Internal Medicine, and it's about survival. Dr. Donald Redelmeier and
his colleague Sheldon Singph found that actors and actresses who have won Oscars live,
on average, 3.9 years longer than other performers who have never won Oscars. Dr.
Redelmeier is in Toronto and joins us now.
Dr. Redelmeier, how did you conduct this study?
Dr. DONALD REDELMEIER: What we did is, we identified every actor and actress
who's ever been nominated for an Academy Award in either a supporting role or a
leading role over the full history of the Academy Awards since 1929.
SIEGEL: What does this tell you? What do you think is the cause of the greater
longevity among those actors and actresses who won Academy Awards.
Dr. REDELMEIER: One possible theory is that winning an Academy Award improves
a person's self-esteem and gives them a much greater resilience to the normal stressors
that confront us on a day-to-day basis. And that, in turn, causes changes in the
hypothalamic, pituitary, adrenal glands of the body or the immunological systems, and
so that much less damage occurs over the years.
SIEGEL: If this is true, do you think we should find then that, say, the Academy Award
winners among the film editors or the special effects people would also outlive their
colleagues or do you think it requires the adulation that only star actors and actresses get
to add the extra 3.9 years to a life span.
Dr. REDELMEIER: Well, more research is always needed. Another possibility is that it
isn't due to a person's internal biology, but it reflects their external behavior—i.e., that
EXERCISES for Section D 327
stars live lives under continuous scrutiny, and so because of that, they need to sleep
properly every night, eat a balanced diet at every meal, exercise regularly every day in
order to preserve their glamorous image. And so it's those external behaviors rather than
the internal peace of mind that confers a much greater survival benefit than is generally
appreciated.
15. Study: Better primary care increases hospitalization
Researchers set out to show that giving sick people better access to family doctors keeps
them out of the hospital. But to the surprise of everyone involved, the study found just
the opposite.
Doctors apparently end up diagnosing more ills, including ones that probably
would otherwise go unnoticed.
"I went in knowing that primary care could help keep these patients out of the
hospital. That was my passion. I was exactly wrong," said Dr. Eugene Z. Oddone of
the Veterans Affairs hospital in Durham, N.C.
He and Dr. Morris Weinberger of the VA hospital in Indianapolis had thought the
experiment would prove the obvious: Better primary care keeps people healthier,
reducing hospital admissions by about one-third and saving money.
Working with nine VA hospitals, they offered poor, seriously ill veterans the kind
of care available in most HMOs—ready access to a nurse, a family doctor in charge of
their case, reminders of appointments and follow-up calls.
After six months of this attention, hospitalizations actually rose by one-third.
"We were more surprised than anybody," Weinberger said.
The doctors said their study, published in Thursday's issue of the New England
Journal of Medicine, illustrates one of the difficulties of refashioning the health care
system: Even common-sense ideas need to be tested to make sure they work.
Furthermore, for some, it raises doubts about an article of faith among doctors—
that catching and treating diseases early will make people healthier in the long run.
In an accompanying editorial, Dr. H. Gilbert Welch of Dartmouth Medical School
said the study forces doctors to consider a "heretical view."
"Instead of conferring benefit, closer scrutiny of the patients simply led to more
medical care and perhaps to harm," he said. "We can no longer assume that early
intervention is always the right thing to do." Associated Press, May 30, 1996
16. Bad hair can give self-esteem a cowlick, study says
People's self-esteem goes awry when their hair is out of place, according to a Yale
University researcher's study of the psychology of bad-hair days.
People feel less smart, less capable, more embarrassed and less sociable, research-
ers said in the report released Wednesday.
And contrary to popular belief, men's self-esteem may take a greater licking than
women's when their hair just won't behave. Men were more likely to feel less smart and
less capable when their hair stuck out, was badly cut or otherwise mussed.
"The cultural truism is men are not affected by their
appearance," said Marianne
LaFrance, the Yale psychology professor who conducted the study. "(But) this is not
just the domain of women."
328 CHAPTER 15 Cause and Effect
The study was paid for by Proctor & Gamble, which makes hair-care products.
The Cincinnati-based company would not discuss how much the study cost or what they
planned to do with their newfound knowledge about the psychology of hair.
Janet Hyde, a psychology professor at the University of Wisconsin at Madison who
studies body image and self-esteem, said personal appearance can have an enormous
effect on people, especially adolescents.
But Hyde said she was surprised to hear bad hair had a stronger effect on men than
on women in some cases.
For the study, researchers questioned 60 men and 60 women ages 17 to 30, most of
them Yale students. About half were white, 9 percent were black, 21 percent were Asian
and 3 percent were Hispanic.
The people were divided into three groups. One group was questioned about times
in their lives when they had bad hair. The second group was told to think about bad
product packaging, like leaky containers, to get them in a negative mind-set. The third
group was not asked to think about anything negative.
All three groups then underwent basic psychological tests of self-esteem and self-
judgment. The people who pondered their bad-hair days showed lower self-esteem than
those who thought about something else. .. .
LaFrance, who has also studied the psychology of smiles, facial expressions and
body language, said she would continue to look into the effects of bad hair. "We all do
research that at first pass might seem quite small," she said. "Yes, some of my
colleagues said, 'That's interesting, ha, ha.' But then, when we talk about it, people are
interested." Associated Press, January 27, 2000
17. In the mid-1970s a team of researchers in Great Britain conducted a rigorously designed
large-scale experiment to test the effectiveness of a treatment program that represented
"the sort of care which today might be provided by most specialized alcoholism clinics
in the Western world."
The subjects were one hundred men who had been referred for alcohol problems to a
leading British outpatient program, the Alcoholism Family Clinic of Maudsley Hospital
in London. The receiving psychiatrist confirmed that each of the subjects met the
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