Tuesday, May 11, 2010

Your personal opinion does not trump scientific studies

As a scientist, one of my big pet peeves is when someone tries to use a personal anecdote to disprove a scientific study. "Cigarette are bad for you?! But my grandpa chain smoked until he was 96, and he was healthy as an ox!"

Great for your grandpa! ...But that's irrelevant.

The whole purpose of science is to reduce our biases. Looking at your sample size of one (Grandpa) is going to lead you to the wrong conclusion about what's going on with smoking. Your grandpa was an outlier - and while that is interesting, the vast majority of people suffer harmful effects from smoking.

But my bigger pet peeve is when someone's culture, personal opinion, or political belief stands in the way of them accepting science.

For example, during our unit on aggression in my Social Psychology class, we talked about cultural causes for aggression. One example was the Southern Culture of Honor. People who grow up in this culture see a perceived insult as a threat to their ego, which increases testosterone levels* and violent cognitions, and can lead to acts of violence. Southern cities and states have much higher White homicide rates than those populated by northerners**, and in Southern states homicides exceed suicides.

Effects of Insults on Testosterone levels in Southerner and Northerner Participants
When I mentioned this in a tweet, some of my Southern followers got angry and said it wasn't true, and tried to provide anecdotal evidence about how kind and helpful Southerners are. Your neighbors may be sweet, but that doesn't negate an overall trend. Scientific studies aren't saying that all southerners are homicidal maniacs. Though you know, getting angry at a perceived insult doesn't exactly help your cause...

Another topic within aggression that really riles people up is spanking. Numerous studies have been done showing that spanking children increases antisocial*** and aggressive**** behavior. But when people who have been spanked or spank their children hear about this, they get very defensive. I can't recall the number of times I've heard "Well I was spanked, and I turned out fine!" or "I spanked my kids and now they're little angels!"

I'm sorry, but 1) Your specific experience does not negate the average response seen in hundreds of families, and 2) Your evaluation isn't necessarily correct. You could very well have had an increase in antisocial or aggressive behavior, but you didn't have a psychologist assessing your behavior, did you? I'd really like to see a psychological study on why people like to defend spanking. Do they hate thinking that their parents did something wrong? Do they hate having to come up with a better (and possibly less easy) disciplinary action?

And last, but not least: political beliefs that get in the way of accepting science. The one that bugs me the most are feminists who are such huge supporters of female equality that they simply cannot accept that males and females do differ in certain ways. For one, you kind of can't ignore that (biologically typical) males and females differ physically - we kind of have different reproductive organs and chromosomes. We also have different secondary sex characteristics - males are going to be slightly stronger and larger on average.

And because our biology differs, it's not insane to suggest our psychology differs. Saying men are better in some areas and women are better in others does not mean one is superior to another. Saying men may have certain mating strategies and females may have different ones does not mean one is morally superior, or that either are things we should actually do - humans are not simply slaves to their biology, after all. There are differences between the sexes in almost every species where there are two different sexes - humans aren't exempt. To deny these differences because they don't jibe with your political beliefs is simply unscientific.

Now, I know I'm not perfect. There have definitely been times where I've been skeptical of a study when I personally didn't like the results - it's human nature (especially when the study is saying something delicious is bad for your health). But the thing about being a scientist is reducing our biases as much as possible. So next time you find yourself giving anecdotal evidence, remember: Your personal opinion may be an interesting new hypothesis, but until you do a study of your own, it does not trump previous scientific research.

* Cohen et al (1996) Culture of Honor: The Psychology of Violence in the South
**Myers (2008) Social Psychology
*** Strauss et al (1997)
**** Taylor (2010) in Pediatrics


  1. If the outliers all share the same DNA, would that not lead one to believe that perhaps there was more to the story?

  2. I seriously doubt the probability of ALL outliers having a similar DNA.   Just considering the various millions upon millions of differences between two individuals and their gene expressions.  Not to mention the trillions of socio-economic and environmental factors that play a significant role in gene expression.

  3. That feminist argument.  800% win.

  4. I enjoy the clarity of this article and look forward to reading more.  The anti science arguments I have trouble with are when someone accuses me of not believe something because it's not proven "on paper."  There's lots of terrible unscientific "studies" "on paper."  The other is being accused of close mindedness.  I'm always open to new evidence just don't expect me to believe something based on a feeling or a cultural tradition.

  5. I believe it's human nature to criticize studies with results we don't like. Therefore, what do you make of the fact that some critics of religion sent hate mail to a scientific journalist who reported on a study that found that children who attended church more frequently were better adjusted than their peers (look up 'Melinda Wenner,' 'religion,' 'Bartkowski' and 'hate mail')?

  6. Ehelgersen: did anyone claim that there are no stupid atheists? :D

  7. I'm not saying that there aren't stupid atheists - believe me, as an old song goes, "The world is full of stupid people," and it doesn't matter what their religious persuasion is. I am just saying that sometimes when people, even highly intelligent people, get emotionally invested in a particular point of view, they get upset when scientific studies show their point of view might not be factually correct. So I'm just wondering what our moderator might think of studies showing that children of more religious observant parents might be better off in some respects than other kids. (Note: I tend to think that these results aren't due to religion per se but to the fact that religious families might have advantages in other areas, such as less family conflict and less drug use.)

  8. Just discovered your blog. LOVE IT! How I wish you were near my age and in my part of the country. I'd vote for you for president.

  9. I agree science is a great platform for an argument, but it is equally important to make sure that the scientific information you are looking at has been collected in a balanced fashion. many scientific studies are done by companies or organizations that are looking for a certain outcome, and they will pay to have this outcome happen. I'm not saying these correlate to any of the arguments that you discuses, however they are still things that need to be taken into consideration when looking at scientific studies.

  10. Jen, what do you think of the spanking study's findings that children whose mother had no religious preference were more aggressive, even when other variables were controlled?

  11. Also, Jen, you very rightly defended Jessica Alquist, the young woman who has received hate mail for wanting a reference to God removed in her school. Are you also going to defend Melissa Wenner, the journalist who received hate mail for writing a press release on a study showing that children who attended church were better adjusted than their peers?

  12. Sorry, I meant to say 'Melinda' Wenner.

  13. Science is peer-reviewed. That stuff financed by companies who pay for an outcome? Not peer-reviewed. What you are talking about isn't "scientific" research, by definition.

  14. "
    a study that found that children who attended church more frequently were better adjusted than their peers "

    Was there any mention in this study of those children who  had Mom & Pop's religion  forced down their throat and then as those children matured, they became atheists?

  15. No, that wasn't the point of the study.

  16. Do you have a problem with the studies showing that children who attend church more/have more religious families are better adjusted?

  17. You should have mentioned global warming in there, too. The motivations for denying that global warming is both A) real, and B) caused by humans are entirely political. Whether it's because the denialists think poorly of "environmentalists," or because they fear that the Big Bad Government is going to start forcing them to drive dinky little putt-putt cars or cause their power bill to triple, or — horror of horrors — actually impose regulations on oil companies or automobile manufacturers, because that's *gasp!* COMMUNISM!!! It's a reactionary attitude. And the lengths they'll go to "disprove" it are ridiculous at best. For example, there's the classic standby "Hey. Look at all this snow outside. Where's your global warming now?" Apparently they missed the memo where global warming is an increase in the global average temperature. Key word there being "average." Some people think that their personal anecdotes (severe winter weather in their town) somehow disproves decades of study by the scientific community.

    If a scientific theory ends up being something that affects public policy, you can be damn sure someone is just going to outright deny the validity of it. You never see politicians deny general & special relativity or quantum mechanics or atomic theory or the germ theory of disease or cell theory or periodic law, because accepting the validity of these things has no bearing on matters of policy. Nobody gets up in arms if you say "Matter is made of atoms."  But if you say "Hey, guys. You know how fossil fuels are the life blood of our economy? Well, it turns out that us burning all this oil, coal, and gas is increasing the CO2 content of the atmosphere and warming the planet, and that might possibly be bad," somebody is going to freak out about it, because now we're dealing with economic externalities, and acknowledging that those externalities exist both opens the door for the possibility of government intervention and means that some companies' business model is flawed, and changing that model could cost them billions. Better to just pretend the problem doesn't exist, or better yet, engage in a massive PR campaign to convince the entire public the problem doesn't exist. "Screw what the science says. Accepting the science means the socialists win."

    Ideology is a powerful force, and for some, no amount of evidence will convince them they're wrong. The global average temperature could spike by five degrees, places like Miami and the Maldives could be underwater, and they'd still be "Nope. Global warming isn't real. Can't let the government and those hippie radicals force more efficient vehicles and clean power sources on everyone."