Tag Archives: correlation without causation

Participating in culturally elite activities related to lower BMI?

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A new sociological study suggests there is a relationship between participating in certain cultural activities and having a lower BMI:

The study uses survey data from 17 nations, most of which are in Europe. In each country, a representative sample of the population was asked not only about height and weight, but also about time spent in a variety of activities. These included reading, going to cultural events, socializing with family and friends, attending sporting events, watching TV, going shopping, and exercising.A scale that measures interest in ideas, art, and knowledge—by surveying the amount of time spent reading, attending cultural events, going to movies, and using the Internet—is associated as strongly as exercise with a lower body-mass index, or BMI (a measure of weight relative to height). In other words, reading and exercise appear similarly beneficial in terms of BMI.

In contrast, people participating in other activities such as watching TV, socializing, playing cards, attending sporting events, and shopping have higher average BMI. Although time spent reading and time spent watching TV both expend few calories, one is associated with lower weight, and the other with higher weight…

So why might reading and related cultural activities be associated with thinness? The social meaning of the activity rather than the activity itself must be important for weight control. Leisure-time activities involve more than the calories burned; they also reflect differences across social groups in motives and means for good health.

These sound like interesting findings but I wonder if this is a classic example of “correlation does not imply causation.” Since these cultural activities might be related to social class, how do these findings line up with current statistics about weight (and health) by social class?

Ban on lead the cause of drop in crime?

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Here is a quick overview about how the reduction of lead exposure in society could have contributed to the recent decline in crime rates:

One of the most fascinating questions in American sociology, political science, and public policy is the substantial decline in violent crime in America has been falling for two decades after a near-peak in 1991; the homicide rate hit a 50-year low last year despite the recession. There are a lot of interesting theories, none that (as far as I’ve read) is considered dominant. In November, Llewellyn Hinks-Jones wrote a compelling piece for the Atlantic about crime rates and the declining price of cocaine; there’s the evergreen broken-windows theory; Steven Levitt’s abortion theory (PDF); increasing incarceration rates; the destruction of massive public-housing complexes; improved trauma care; and many more. I was reminded of another one when reading up on public housing yesterday, thanks to a brief aside in Beryl Satter’s masterful Family Properties (emphasis mine):

The “peril to life and safety of the inhabitants” of slum buildings was often of a gruesome sort. Residents were injured on poorly lit stairways or ones with broken banisters. They were knocked out by falling plaster. They were scalded by the escaping steam of malfunctioning radiators. They perished in fires in buildings where fire escapes had collapsed from neglect. Their infants’ limbs were gnawed by rats. Each year approximately twenty-five children died from eating lead-filled paint chips. Others survived lead poisoning but were left mentally disabled.

Satter’s numbers come from a Chicago Daily News report from 1963. To put that in context, between 16 and 46 young Chicagoans died from accidents each year between 2002 and 2006, the leading cause of death in the 1-14 age group. In a 1962 Trib report, a board of health poison control pilot study found 35 deaths from 1959 to 1961: “Most of the victims were from 1 to 5 years old and came from rundown slum area buildings….” 465 cases were treated at County Hospital in those two years, and another 65 suffered severe brain damage…

That’s correlation, but what about cause? The great young science writer Jonah Lehrer explains the believed chain of causation from lead poisoning to violence (emphasis mine):

Here, for instance, is a recent PLOS study from the Cincinnati Lead Study, in which the blood lead level of babies born in poor areas of Cincinnati were repeatedly measured between 1979 and 1984. Twenty years later, the researchers tracked down these subjects and put them in MRI machines, allowing them to measure the brain volume of participants. The researchers found that exposure to lead as a child was linked with a significant loss of brain volume in adulthood, particularly in men. Furthermore, there was a “dose-response” effect, in which the greatest brain volume loss was seen in participants with the greatest lead exposure. What’s especially tragic is that the loss of volume was concentrated in the prefrontal cortex, a part of the brain closely associated with executive function and impulse control.

Several things come to mind:

1. Perhaps we simply need more scientific studies in order to sort this out yet a one cause answer to the drop in crime may be really difficult to find. Human behavior within a social context is complex.

2. I wonder if this hints at an already existing and likely to grow set of studies that discuss how everyday substances negatively affect us.

3. The person who is able to conclusively/definitively find the causes in the drop in crime will be either heralded, attacked from all sides, and perhaps both.

American Academy of Pediatrics: television has no positive effects on children under two

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Here is a new recommendation from the American Academy of Pediatrics about children under two watching TV:

Their verdict: It’s not good, and probably bad.

Media, whether playing in the background or designed explicitly as an infant educational tool, “have potentially negative effects and no known positive effects for children younger than 2 years,” concluded the AAP’s report, released Oct. 18 at the Academy’s annual meeting in Boston and scheduled for November publication in the journal Pediatrics. “Although infant/toddler programming might be entertaining, it should not be marketed as or presumed by parents to be educational.”…

As screens proliferated, so did research. “There have been about 50 studies that have come out on media use by children in this age group between 1999 and now,” said Ari Brown, a pediatrician and member of the AAP committee that wrote the new report…

Three studies since 1999 have tracked educational television use and language development, and they found a link between increased TV time and developmental delays. Whether that’s a cause or effect — parents who leave kids in front of televisions might simply be poor teachers — isn’t clear, nor are the long-term effects, but the AAP called the findings “concerning.” In the same vein, there may also be a link to attention problems.

Several thoughts about this:

1. This article suggests researchers have found a correlation, not necessarily causation. But since researchers have not found any positive effects, they must feel confident in issuing this recommendation.

2. Does research suggest that television has some positive effects for children over two years old? Overall, are there studies that suggest television has positive effects for adults?

3. What does this do for children’s programs and videos? What about all of those “Baby Einstein” videos? Will new cottage industries spring up to fill this void?

Whether Facebook increases the number of divorces

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You might have seen certain figures bandied about how often Facebook is cited in divorce cases: this story says, “Two-thirds of the lawyers surveyed said that Facebook was the “primary source” of evidence in divorce proceedings.” But is it fair to then say that Facebook is a primary driver of divorce proceedings? Carl Bialik says the numbers are more complicated than many news stories would lead you to believe:

Some lawyers do say that they see Facebook playing a bigger role in divorce these days, that doesn’t mean the site destroys marriages…

“Correlation is not causation,” Thomas Bradbury, professor of psychology at the University of California, Los Angeles, wrote in an email. “Divorce has been around for a long time, long before these sorts of possibilities were present; the newly available information does add a new flavor to relationship maintenance and dissolution, but I don’t think it changes the basic processes that underlie change and deterioration in relationships.”…

These issues are symptoms of a larger issue in divorce research: “It’s very hard to separate out the causes” of divorce, says Andrew Cherlin, a sociologist and divorce researcher at Johns Hopkins University.

“To do this kind of research requires a huge amount of persistence,” said George Levinger, professor of psychology emeritus at the University of Massachusetts.

Part of the reason is that it is hard to pinpoint a single reason or even a set of reasons for any marital split…

Some researchers have asked divorcees why they divorced, and gotten conflicting results from men and women. Others have looked for factors that predict whether couples divorce. “There are many social, cultural, and behavioral predictors of divorce,” W. Bradford Wilcox, director of the National Marriage Project at the University of Virginia, wrote in an email.

Other academics examine couples’ behavior, seeking clues that might predict marital dissolution.

It sounds like this a more complicated methodological issue that still needs to be worked out by researchers: how exactly can one identify the primary cause or causes of divorce? Just because Facebook is mentioned as contributing to a divorce does not mean that it causes the divorce. As you might expect, Facebook itself says this argument is silly:

A spokesperson for Facebook said: “It’s ridiculous to suggest that Facebook leads to divorce. Whether you’re breaking up or just getting together, Facebook is just a way to communicate, like letters, phone calls and emails. Facebook doesn’t cause divorces, people do.”

It is no surprise that lawyers would want to use Facebook data for a divorce case (or other types of cases such as fraud – one example here). Facebook is often fairly public information and people often post on there without thinking about the potential consequences of sharing such information. It would be interesting to hear more about how this data from Facebook is presented in court and the reactions to it from both judges and the participants in the case.

But I wonder if these sorts of figures and ideas about Facebook and divorce have gained notoriety because they may fit some larger narratives about privacy and information sharing on Facebook as well as voyeurism on the Internet. These figures from lawyers could be presented as evidence that people lead dual lives, one in the offline world and another one in the real world. Whether this is actually the case doesn’t matter as much; what does is that the hot company of recent years, Facebook, can be linked to negative behavior.

An emerging portrait of emerging adults in the news, part 1

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In recent weeks, a number of studies have been reported on that discuss the beliefs and behaviors of the younger generation, those who are now between high school and age 30 (an age group that could also be labeled “emerging adults”). In a three-part series, I want to highlight three of these studies because they not only suggest what this group is doing but also hints at the consequences.

Almost a week ago, a story ran along the wires about a new study linking “hyper-texting” and excessive usage of social networking sites with risky behaviors:

Teens who text 120 times a day or more — and there seems to be a lot of them — are more likely to have had sex or used alcohol and drugs than kids who don’t send as many messages, according to provocative new research.

The study’s authors aren’t suggesting that “hyper-texting” leads to sex, drinking or drugs, but say it’s startling to see an apparent link between excessive messaging and that kind of risky behavior.

The study concludes that a significant number of teens are very susceptible to peer pressure and also have permissive or absent parents, said Dr. Scott Frank, the study’s lead author…

The study was done at 20 public high schools in the Cleveland area last year, and is based on confidential paper surveys of more than 4,200 students.

It found that about one in five students were hyper-texters and about one in nine are hyper-networkers — those who spend three or more hours a day on Facebook and other social networking websites.

About one in 25 fall into both categories.

Hyper-texting and hyper-networking were more common among girls, minorities, kids whose parents have less education and students from a single-mother household, the study found.

Several interesting things to note in this study:

1. It did not look at what exactly is being said/communicated in these texts or in social networking use. This study examines the volume of use – and there are plenty of high school students who are heavily involved with these technologies.

2. One of the best parts of this story is that the second paragraph is careful to suggest that finding an association between these behaviors does not mean that they cause each other. In other words, there is not a direct link between excessive testing and drug use. Based on this dataset, these variables are related. (This is a great example of “correlation without causation.”)

3. What this study calls for is regression analysis where we can control for other possible factors. It would then give us the ability to compare two students with the same family background and same educational performance and isolate whether texting was really the factor that led to the risky behaviors. If I had to guess, factors like family life and performance in school are more important in predicting these risky behaviors. Then, excessive texting for SNS use is an intervening variable. Why this study did not do this sort of analysis is unclear – perhaps they already have a paper in the works.

Overall, we need more research on these associated variables. While it is interesting in itself that there are large numbers of emerging adults who text a lot and use SNS a lot, we ultimately want to know the consequences. Part two and three of this series will look at a few studies that offer some possible consequences.