Okay. Something does not compute.

Last few days everybody is chortling about a shift in % of Republicans who say they don't believe in evolution.

According to Pew Research Center, a higher percentage of Republicans agreed with the statement that "humans ... have existed in their present form since the beginning of time" in 2013 than in 2009.





One fairly annoying thing is that the information that Pew disclosed about the survey makes it impossible to determine what percentage of Democrats actually believe in "naturalistic" as opposed "theistic" evolution.

Pew's survey item is bifurcated. First, survey participants respond to the question, "Which comes closer to your view? Humans and other living things have [1a] evolved over time [OR] [1b] Humans and other living things have existed in their present form since the beginning of time?" Those who select [1a], are then asked:

And do you think that [2a] Humans and other living things have evolved due to natural processes such as natural selection, or [2b] A supreme being guided the evolution of living things for the purpose of creating humans and other life in the form it exists today?

In both 2009 & 2013, those who selected answer 1a-- "evolved over time" -- split about 60:40 as between 2a & 2b-- the "naturalistic" and "theistic" versions of evolution, respectively.



As a result, only 32%, in both surveys, indicated that the believed in the "naturalistic" position that " Humans and other living things have evolved due to natural processes such as natural selection."





Pew tells us in the most recent survey ( Humans and other living things have existed in their present form since the beginning of time." It also tells us that 67% of Democrats, "up" from 65% in 2009, "believe in evolution," or in other words that 2/3 of them selected 1b.

Pew tells us in the most recent survey ( in its web page summary and in its Report ) that only 27% of Democrats selected 1a, the "creationist" position that "

But it doesn't tell us -- not on its web page summary, not in the body of its Report, not in the reported "toplines"; not anywhere -- what % of Democrats chose the "naturalistic" (2a) and what % the "theistic" (2b) evolution positions.



Frankly, that's lame.



It's lame, first, because the answer to that question is really interesting and important if one is trying to make sense of how ordinary Americans reconcile their cultural identities, which are indicated by both their political affiliations and their religious practices (among other things), with belief in science.



Second, it's lame because this sort of deliberate selectivity (make no mistake, it was deliberate: Pew made the decision to include the partisan breakdown for only half of the bifurcated evolution-belief item) subsidizes the predictable "ha ha ha!" response on the part of the culturally partisan commentators who will see the survey as a chance to stigmatize Republicans as being distinctively "anti-science."



If in fact, only a minority of Democrats are willing to endorse "naturalistic" evolution -- if a majority of them refuse to assent to a theory of human beings' natural history without God playing a role in guiding it -- then that makes "ha ha ha ha ha!" seem like an unreflective response to a complicated and interesting phenomenon.





But actually, Pew lulled those who are making the response into being this unreflective by deliberately (again, they had to decide to report only a portion of the evolution-survey item by political affiliation) failing to report what % of Democrats who indicated that they "believe in evolution" accept the "naturalistic" variant.

I'd be surprised if more than a minority did. That would be a significant break with past survey results . For a majority of Democrats to be "naturalistic" evolutionists, they would have to outnmber "theistic" Democrats by a margin of 3:1.

But hey-- I'd love to be surprised, too! An unchanging world is dull. But a world that doesn't change in its catering to petty cultural partisanship is both dull & disappointing.



All that aside , the finding that a greater proportion of Republicans now believe in "creationism" -- & not either theistic or naturalistic evolution -- than in 2009 is pretty darn interesting!



But what exactly has changed?



[A] Republicans are "switching" from belief in evolution (naturalistic or theistic) to creationism; or [B] creationists are switching their party allegiances from Democrat or Independent to Republican &/or evolutionalists (theistic and naturalistic) are switching from Republican to Democrat or Indepedent.

But a world that doesn't change in its catering to petty cultural partisanship is both dull & disappointing., the finding that a greater proportion of Republicans now believe in "creationism" -- & not either theistic or naturalistic evolution -- than in 2009 is pretty darn interesting!But what exactly has changed?There are two obvious possibilities:

Either [A] or [B] would be really interesting, but they would reflect very different processes.

So which is it?



Pew doesn't tell us directly (why?! I don't get the attitude of this Report; very un-Pewlike) but we should be able to deduce the answer from what they do report -- the population %s and the partisan breakdowns on "creationism" in 2009 and 2013.



Logically, if the fraction of the overall U.S. population who identifies as creationist stayed same, & more Rs are now identifying creationists, then [B]-- party-shifts by either evolutionists, creationists, or both -- must be correct.



And in that case,the proportion of Ds & Is who are creationists would have to be correspondingly lower.

Alternatively, If the proportion of Rs who are creationists went up but the proportion of Ds & Is who are creationists stayed same, then [A]-- Republicans are changing position -- would be the right answer.

And logically, in that case, the % of the U.S. public overall who now say they are "creationists" would have had to have gone up.

Now that would be truly surprising -- huge news -- because the %s on creationism-vs-evolution haven't changed for decades.



But not surprisingly, Pew reports that "the share of the general public that says that humans have evolved over time is about the same as it was in 2009, when Pew Research last asked the question.":

The same fraction of the U.S. public -- approximately 1/3 -- believes in "naturalistic" evolution today as did then. The 33% who selected the "creationist" response to the bifurcated survey item in 2013 is statistically indistinguishable from the 31% who did in 2009.

So ... if the population frequency of creationism didn't increase, and the proportion of Republican's who now identify as "creationists" did, either creationists are switching to the Republican party or "evolutionists" (theistic or naturalistic) must be switching to Democrat or Independent -- option [B].

But, logically, then, the proportion of "evolutionsists" who are now identifying as either Democrat or as Independent must have risen by an amount corresponding to the increase in "creationists" now identifying as Republican, right?

Nope. Pew says that the division of "opinion among both Democrats and independents has remained about the same":

Ah.

So if the percentage of Democrats and Independents who identify as creationist has stayed constant, and the proportion of Republicans has increased, [A] --Republicans are "switching" their views on evolution-- must be the answer!

But if the proportion of Republicans who are creationists has significantly increased while the division of "opinion among both Democrats and independents has remained about the same," the total proportion of the population that embraces creationism must be significantly higher. . . . Except that Pew says "the share of the general public that says that humans have evolved over time is about the same as it was in 2009, when Pew Research last asked the question."

So, something does not compute.

At a minimum, Pew has some 'splainin to do, if in fact it is trying to edify people rather than feed the apptetite of those who make a living exciting fractious group rivalries among culturally diverse citizens.

Has anyone else noticed this?

Right away when I heard about the Pew poll, I turned to the results to see what the explanation was for the interesting -- truly! -- "shift" in Republican view: Were Republicans changing their positions on creationism or creationists changing their party allegiance?

And right away I ran into this logical inconsistency.

Surely, someone will clear this up, I thought.

But no.

Just the same predictable, boring "ha ha ha ha!" reaction.

Why let something as silly as logic get in the way of an opportunity to pound one's tribal chest & join in a unifying, polarizing group howl?

Happy New Year, Liberal Republic of Science ....

Update on Thursday, January 2, 2014 at 6:08PM by on Thursday, January 2, 2014 at 6:08PM by Dan Kahan @MW offers a logical & plausible mathematical proof of how the proportion of Republicans who are "creationists" could go up while the proportions of Democrats and Independents as well as the proportion of the general population that is "creationist" all stayed (according to Pew) "about the same." The short of it is that the "about the same" population frequency of creationism actually includes a statistically nonsignificant increase that is concentrated disproportonately in the portion of the sample that identifies as Republican in 2013. So a nonsignificant -- statistically & practically -- increase in the proportion of the population who "disbelieves" evolution drives the statistically significant & apparently hugely meaningful decrease in the % Republicans who "disbelieve" it. Does that mean one can one say that insofar as a greater proportion of Republicans but "about the same" proportion of Democrats and Independents are now creationsits means a greater percentage of the overall public is creationist than in 2009-- my position [A]? No, at least not at a 0.95 level of confidence. Well, then, can one say instead that since the proportion of the population who disbelieves evolution hasn't increased, "the drop in Republican belief doesn’t appear to be people changing their minds about evolution so much as people who already didn’t believe in evolution becoming Republicans"-- my position [B]? And that therefore the Pew result corroborates that the Republican Party is falling "increasingly out of step with the rest of America’s political views"? Obviously, one can say that, but that's definitely not supported by the survey results, because in fact the only way (or only way proposed so far-- take your own shot at solving the paradox) for the proportion of Republicans who are classified as "creationist" to go up and the proportion of Democrats and Indepedents as well as the proportion of creationists in the populaiton all to have remained "about the same" is for the population frequency of creationists actually to have risen -- but by a statistically nonsignificant amount. But it is predictable that people will overlook the mathematical inconsistency -- which will persist until Pew gives an account that resolves it-- and interpret the data as fitting their own preconceptions, which they will then treat as supported by the data. Well, if in fact the only way to explain how "Republcans' belief in evolution has plummted!" is to observe that the percentage of creationists in the population as a whole went up by an amount that pretty much everyone would have to agree is statistical noise, then maybe we should reconsider whether anything interesting has happened at all since 2009? But then again, why let logic drown out the noise of embarrassingly, painfully unreflective jeering at the party a majority of whose members believe God had something to do with the natural history of humans? (What's that you say? A majority of people in our Party believe that, too? Shhhhhhhhhhhhhhhh.).