William M. Briggs

Statistician to the Stars!

That Conservatives Smell Different Than Progressives Study Stinks

Some brave conservatives about to tour an American university campus?

Some brave conservatives about to tour an American university campus?

Several readers asked me to examine the peer-reviewed study “Assortative Mating on Ideology Could Operate Through Olfactory Cues” by Rose McDermott, Dustin Tingley, and Peter K. Hatemi appearing in the American Journal of Political Science.

It’s showing up everywhere. Like the Powerline blog, also in Pacific Standard, and The Week, and of course The Washington Post.

The paper opens with a proposition which is surely false, though it is asserted by many authorities, “Similarity between spouses is common across domains, but in humans, long-term mates correlate more highly (between 0.60 and 0.75) on social and political attitudes than almost any other trait, with the exception of religion”. I would have guessed race, followed closely by geographical and age. But skip it.

“Olfactory mechanisms have proven important in mate seeking and reproduction in both humans and animals because smell may signal mate immunocompetence, social compatibility, or other characteristics associated with mate quality and optimal reproduction.” Cue hippy joke #1.

While you’re at it, cue the amygdala, too, a pea-sized pair of brain “organs” which, as near as I can tell, account for every single human behavior that can be studied by academics. Our authors call to it here, too.

Here’s the question: “Why and how might smell signals be linked to political ideology?” Well, smell helps “maximize prospects for disease avoidance, cheater detection, defense against out-groups, and social cohesion”. Cue hippy joke #2.

Hey, did you know that “greater disgust sensitivity, which is intimately interconnected with the neural substrates of smell, predicts more conservative positions, particularly around issues involving morality and sexual reproduction”? If this is true—and it is peer reviewed—it must imply that conservatives excel at sniffing out the cheesy arguments of their unwashed opponents.

Whatever it is is in the genes, too. “Suggestively, Hatemi et al. (2011) identified several genomic regions that account for variation in ideological orientation, one of which contained a large number of olfactory receptors.” That “suggestively” actually means, “Oooh, we hope it’s true!”

Tying it all together:

If social attitudes are linked to odor, as the literature suggests, then one mechanism that odor preferences transfer from parents to children may operate through their mother’s choice of mate. In this way, social processes may drive some of the pathways by which individuals come to prefer those whose ideological “smell” matches their own.

The Just-So stories having ended, we proceed to the experiment itself, in which “participants rated the attractiveness of the body odor of unknown strong liberals and strong conservatives”. Ten lefties and 11 righties “provided body odor samples” (“menstruating or pregnant women were excluded”). One other sample was excluded: I couldn’t discover whether it was a leftie or rightie.

Affiliation was decided by a questionnaire (7 point scale), and so was smell (5 point). On an 11-point scale, dear reader, rate your belief in the validity of these “instruments”.

Anyway, the noses went to work. Data was collected. People were thanked. Now it is here is where you would expect a simple summary, maybe some pictures, showing the distribution of smelliness broken down by the evaluators’ and targets’ political affiliations. Did the raw data reveal that leftie evaluators prefer the smell of target lefties? And did conservative evaluators dislike the smell of leftie targets?

Alas, we shall never know. For why use actual data when you can have a statistical model instead? Actually three models. Regression of course (one logistic, two Gaussian). As if the uncertainty in a 5-point smelliness scale is well approximated by a normal distribution. And what’s with shoehorning in strange terms like “absolute value of the difference between the target’s and evaluator’s ideology, multiplied by negative 1” and “Avg. Target Attract” and “Avg. Eval. Attract”?

No wee p-values for the logistic model, but why worry when the results are “consistent with our theoretical expectations.” Sadly, consistent with is now our highest standard of evidence. Skip it.

Oh, wait, now I get it. The “absolute value of the difference between the target’s and evaluator’s ideology, multiplied by negative 1” is what had the wee p-values, and an effect size of about 0.02. That’s for a change on a smelly scale of 1 to 5. And don’t forget the maximum political difference can only be 6, so that the maximum effect can only be 0.12. At best: if the model is good.

That’s it. That’s the study. That wee, which is to say, trivial effect confirmed by a wee p-value, all wrapped up in an inappropriate model. But the authors still say “individuals find the smell of those who are more ideologically similar to themselves more attractive than those endorsing opposing ideologies”.

The authors added a few hundred more words in an attempt to escape the obvious. They never make it. But the press believed they did.

12 Comments

  1. No hippy jokes in footnotes? Sad, just sad.

  2. One supposes that if you consider humans equivalent to gerbils then one would certainly be looking for a relationship between smell and mating. Otherwise, it gets a big “yawn” and I’m going back to reading about how people have intelligence and can make rational decisions, even if they don’t want to talk about. Leave this study to furry rodents and skip the human beings.

  3. Briggs

    October 7, 2014 at 9:05 am

    Gary,

    I was relying on you for those.

  4. Great article and many thanks.
    The study needs to be expanded….(tongue in cheek snark\)
    -The fact that once a person gains experience and knowledge they no longer are liberals…and how knowledge changes body odor.
    – Persons who do not acquire knowledge and information to undergo a ‘body odor change’ must therefore have a physical inability to acquire new knowledge and information.
    – That scent is coupled to mate selection then why are so many Liberals not coupled and only practice at it until the odor is overbearing and then leave.
    – The success rate of selection: how many in the control group successfully coupled, married/and or carried on their gene pool with the conclusion that liberal attitudes affect body odor beyond genetics.
    – Who the sniffers are since they are selecting based on the study’s premise and assumption they will select “their own kind”.
    – Finally, the paper failed to address the true outcome of the paper:
    It demonstrates how stupid Liberals are desperate enough to ‘scientisize’ a claim that personal responsibilities, outcomes and success are not the individual’s choice and beyond their control. Its genetic, IQ, society’s fault, climate change etc….and that a larger outside group must correct it because the individual is incapable.

  5. Ye Olde Statisician

    October 7, 2014 at 10:03 am

    Something does smell here.

  6. I guess I could see where political ideology might have a slight effect on how one smells only because political ideology has some affect on where one shops and what hygiene products one uses. I suspect there are more liberals buying organic soaps made on hippie communes in Vermont at Whole Foods vs conservatives buying plain old Ivory soap at Walmart.

    As a parallel, I look around my Colorado neighborhood and 90%+ of all the Subaru owners in my neighborhood are liberals whereas 90%+ of all the Chevy Suburban owners are conservatives, so I suspect political ideology might drive other consumer choices.

    But one’s politics having an effect on one’s biochemistry? No, that’s silly.

    At any rate I’m suspicious of any of these “scientific” studies that purport to tie one’s politics to other odd unrelated metrics (usually at the expense of conservatives).

  7. Mike: I own two Subarus and buy Ivory soap at Kmart.

  8. You smell so bad, you make Right Guard turn left, Speed Stick slow down, Secret obvious, and Sure confused.

    If your feet smell and your nose runs, you’re built upside down.

    Q. What did one eye say to the other?
    A. Between me and you something smells.

    A man walked into a chemist shop and asked for a spray that filled a room with the smell of rotten eggs, stale socks and sour milk.
    “What on earth do you want something like that for?” asked the chemist.
    “I’ve got to leave my flat this morning, and it states in the lease that I must leave it exactly as I found it!”

    Confucius say “Crowded elevator always smell different to midget.”

  9. Briggs,

    What do you call a hippy’s wife?
    Mississippi.

    Two stoned hippies are walking along an old railway track. The first hippy says, “Wow, these stairs go on for miles, man.” And the second said, “It’s these low hand rails that are killing me, man.”

    Why did the stoned hippy drown?
    He was too far out, man.

    First hippy: “What would you do if you saw a spaceman?”
    Second hippy: “Park my van in it, man.”

    Why do hippies wave their arms around when they dance?
    To keep the music out of their eyes.

    How do you know a hippy has been staying at your house?
    He’s still there.

    Why did so many hippies move to Oregon?
    They heard there was no work there.

  10. Can’t tell if the aroma is from the jokes or the rotten eggs tossed at them.

    Gary, say what you will but Fat Freddy’s Cat was the real real reason for the hippie movement.

  11. DAV,
    Despite my college year coinciding with your reference, I was only passingly aware of the genre. A little more into Firesign and National Lampoon.

  12. Thank you very much for dissecting this. Unfortunately now I can’t blame some people’s dislike for me as being caused by my political smell.

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