By JAY JOSEPH
There seems to be no end to illogical and even
comical “findings” from MZ-DZ twin method comparisons, where the original twin
researchers argue that the greater behavioral resemblance of reared-together MZ
(monozygotic, identical) versus same-sex DZ (dizygotic, fraternal) twin pairs
demonstrates the “heritability” of the behavioral characteristic in question.
Among these we find a twin study whose authors concluded in favor of a genetic basis for being a “born again Christian” (65%
heritability), another that found important genetic influences on tea
and coffee drinking preferences, and still another that found that
theheritability of “loneliness in adults” is 48%.
In a similar manner, in an April 13th, 2015
article published in The Independent, British twin researcher Tim Spector argued that
his TwinsUK study findings show that “research with twins suggests picking who
to vote for in an election might have more to do with your genes than the
policies of the parties.”1 Twin research in political
science goes back to 2005 and earlier,2 and has not gone
unchallenged in the field.3 Spector and colleagues asked 612
reared-together pairs of twins born in the United Kingdom “whether they
intended to vote, what their political party of choice was and…their personal
rating of the main party leaders.” Predictably, like most studied behaviors and
behavioral disorders, MZ pairs correlated higher than DZ pairs for several
characteristics, a result that twin researchers attribute to genetics on the
basis of their assumption that MZ and DZ pairs grow up experiencing similar
environments. This is known as the MZ-DZ “equal environment assumption” (EEA).
As I show in my recent book The Trouble with Twin Studies, and elsewhere, the evidence clearly shows that MZ twin
pairs grow up experiencing much more similar environments, and experience psychological
closeness and attachment to a far greater degree, than experienced by DZ twin
pairs. Although most twin researchers now recognize that MZ childhood
environments are more similar, they uphold the validity of the EEA on the basis
of circular arguments and other types of illogical reasoning.4
In a statement that even most of his twin
researcher colleagues would disagree with, Spector upheld the EEA by claiming,
without qualification, that “both identical [MZ] and non-identical [DZ] twins
normally share the same environment while growing up.” This false claim allowed
him to conclude that the greater behavioral resemblance of MZ pairs is caused
by genetic factors. According to Spector:
“We found that voting Conservative [Tory] (or
not) is strongly influenced by genetics. When it came to voting Tory, we found
that 57% of the variability (differences or similarity) between people’s voting
preferences were due to genetic effects. This percentage is called
heritability. That means the identical twins were more likely to vote the same
way than the non-identical twins–suggesting [that] an underlying genetic
influence was stronger than environmental or random factors. For UKIP [UK
Independence Party] voting preferences, there was also a moderately strong
heritability of 51%. This was closely followed by Labour and the Green Party
both with 48%. The exception seemed to be voting for the Liberal Democrats,
which was affected entirely by environment, with no genetic influence.”
Based on accepting both the validity of the
EEA and the controversial “heritability” concept, Spector concluded that the
heritability of voting Conservative (Tory), UKIP, Labour, or Green was
“moderately strong,” whereas there was no genetic influence on voting for the
Liberal Democrats. In addition, Spector concluded that “geography also played a
possible role–as voting for the SNP [Scottish National Party] in Scotland was
also completely environmental.” Apparently, there are genes predisposing people
to vote for some (British) political parties, but not for others!
Suppose that Spector had found that MZ pairs
correlate at 75% for supporting the Tories, and that same-sex DZ pairs
correlate at 25%. Because simple heritability estimates are based ondoubling the MZ-DZ correlation difference, in this case
the heritability of voting Tory would be 100%, which would lead to the absurd
conclusion that “the policies of the parties” had virtually no influence on
whether or not someone voted Tory.
Turning to the candidates running for office,
Spector wrote,
“The question of whether a leader would make a
good prime minister produced mixed responses. David Cameron [Tory] had the
stronger genetic influence on opinions, with 50% heritability, followed by Nick
Clegg [Liberal Democrat] at 37%. Views on all the other party leaders were
purely environmental.”
UK residents carry genes predisposing them to
vote for Cameron or Clegg, according to the logic of Spector and the twin
method, but carry none for the other candidates.
In addition to defending the twin method’s untenable
equal environment assumption, twin researchers of political behavior, and of
behavior in general, focus narrowly on the twins they study, and usually
overlook obvious real-world natural experiments contradicting their claims.5 For example, the people living in “socialist” North
Korea and “capitalist” South Korea are members of the same ethnic population,
but are divided for political and military reasons. Koreans on either side of
the demilitarized zone that separates the two countries hold differing
political views and support different political leaders, for reasons having
nothing to do with genetics. For the same reason, we would expect attitudes
toward “government provided health care” to show marked differences between
people of British ancestry living on either side of the U.S.-Canada border.
Genetic predispositions also do not explain why Germany was heavily anti-Nazi
in the late 1920s, and heavily pro-Nazi just a few years later. The list of
examples is endless.
Spector concluded that “the findings of this
study suggest that our choices at the polling booth may not be as free or
rational as we would like to believe.” Very true, but the reduction of free
will and rationality is not “in the genes,” but is instead a product of
manipulation and propaganda by powerful political and economic (corporate)
forces through education, the media, the Internet, religion, speeches, and so
on. Voting patterns are also influenced by the common practice of parties and
politicians campaigning on the basis of one program, and then carrying out a
different program once in office (usually referred to as “broken campaign
promises”). The Independent is not a satirical
publication, and Spector’s article seems more appropriate for the
science/technology section of The Onion.
Twin researchers in political science continue
to uphold the validity of the EEA in twin studies of behavior,6 at times relying on convoluted and illogical
arguments.7 But the fact remains that MZ pairs’ more similar
political views, party affiliation, candidate choices, and voting patterns can
be completely explained by the more similar treatment they
receive growing up, in addition to their greater tendency to model their
behavior on each other, their much greater levels of closeness, loyalty, and
attachment, and their greater tendency to experience identity confusion than DZ
pairs.8 This conclusion is supported by the ongoing failure
to identify genes for political characteristics at the molecular genetic level.9
Twin researchers sometimes claim that the
arguments of their critics should be questioned because these critics do not
perform twin studies, and therefore are not experts on twins. This occurred in
a recently reopened debate on twin research in American criminology, where
criminologists Callie Burt’s and Ronald Simons’ conclusion that twin studies
are methodologically and conceptually flawed was criticized by twin researchers
in the field. These twin researchers attempted to counter Burt and Simons’
critique, in part, by claiming that they “have never worked with twin data, and
they show no signs of being familiar with the large and substantial body of
work that supports the use of these behavioral genetic methods.”10 Aside from the fact that Burt and Simons possess
great knowledge of the criminology twin and adoption study literature,11 expert status is not always necessary to debunk a
research technique or scientific theory, if the technique or theory is based on
obviously false assumptions.
In fact, people outside of twin research and
behavioral genetics are better equipped to see the glaring problems and false
assumptions underlying studies of twins reared together and of twins reared apart—problems and false
assumptions that twin researchers do not allow themselves to see, or dismiss
with illogical arguments. As the pioneering twin research critic Leon J. Kamin
once wrote,
“The [twin] investigators, after all, tend to
analyze their data in the same ways, reflecting the same theoretical
preconceptions. The problem is nothing so simple as the suppression of
embarrassing data. Theoretical commitment makes it unlikely that embarrassing
patterns within the data will even be noticed.”12
Indeed, theoretical commitment to the twin
method and its equal environment assumption often compels twin researchers to
overlook obvious embarrassing patterns both within their data and in society,
and at times leads them to arrive at absurd conclusions such as the claim that
preferences for some political parties and candidates have a “strong” or
“moderately strong” genetic basis.13
* * * * *
References:
1. Spector, T., (2015, April 13th), General Election 2015: Do Your Genes Determine How You Vote? The
Independent.
2. Alford et al., 2005, Are Political
Orientations Genetically Transmitted?, American Political Science
Review, 99, 153-167; Joseph, J., (2010), The Genetics of
Political Attitudes and Behavior: Claims and Refutations, Ethical Human
Psychology and Psychiatry, 12, 200-217.
3. Charney, E., (2008a), Genes and
Ideologies, Perspectives on Politics, 6, 292-319; Charney, E.,
(2008b), Politics, Genetics, and “Greedy Reductionism,” Perspectives on
Politics, 6, 337-343; Charney, E., (2012), Behavior Genetics and
Postgenomics, Behavioral and Brain Sciences, 35, 331-358;
Charney, E., (2013), Nature and Nurture, Perspectives on Politics, 11,558-561;
Charney, E., & English, W., (2012), Candidate Genes and Political
Behavior,American Political Science Review, 106, 1-34; Shultziner,
D., (2013), Genes and Politics: A New Explanation and Evaluation of Twin Study
Results and Association Studies in Political Science, Political
Analysis, 21, 350-367.
4. Joseph, J., (2004), The Gene Illusion: Genetic Research in Psychiatry and Psychology
under the Microscope, New York: Algora; Joseph, J.,
(2015), The Trouble with Twin Studies: A Reassessment of Twin Research in
the Social and Behavioral Sciences, New York: Routledge.
5. Like most twin researchers, Spector
believes that “twins provide a unique natural experiment for research.”
6. Alford et al., 2005; Hatemi et al.,
(2014), Genetic Influences on Political Ideologies: Twin Analyses of 19
Measures of Political Ideologies from Five Democracies and Genome-wide Findings
from Three Populations, Behavior Genetics, 44, 282-294.
7. For example, in 2012 Kevin Smith and a
group of leading political science twin researchers concluded that even if the
critics are “wholly correct” that the causes of MZ-DZ differences are
“exclusively environmental,” this finding would “provide reasons for political
science to pay more rather than less attention to the biological basis of
attitudes and behaviors.” It is illogical, however, to state that political
scientists should “pay more attention” to biological influences on political
attitudes and behaviors if explanations for MZ-DZ differences are “exclusively
environmental.” See Smith et al., (2012), Biology, Ideology, and Epistemology:
How do We Know Political Attitudes are Inherited and Why Should We Care?, American
Journal of Political Science, 56, 17-33, p. 17. For a critical
analysis of this study, see Joseph, 2015; Joseph, J., (2013), The Use of the
Classical Twin Method in the Social and Behavioral Sciences: The Fallacy
Continues, Journal of Mind and Behavior, 34, 1-39.
8. See Joseph, 2015, Chapters 7 and 8.
9. Hatemi et al., 2014.
10. Wright et al., (2015), Mathematical Proof Is not Minutiae and Irreducible Complexity Is
Not a Theory: A Final Response to Burt and Simons and a Call to Criminologists, Criminology,
53, 113-120, p. 117.
11. Burt, C. H., & Simons, R. L.,
(2014), Pulling Back the Curtain on Heritability Studies: Biosocial
Criminology in the Postgenomic Era, Criminology, 52, 223-262.
See also Burt, C. H., & Simons, R. L., (2015), Heritability Studies in
the Postgenomic Era: The Fatal Flaw is Conceptual, Criminology, 53, 103-112.
12. Kamin, L. J., (1981), Commentary, in
S. Scarr (Ed.), Race, Social Class, and Individual Differences in I. Q.,
(pp. 467-482), Hillsdale, NJ: Lawrence Erlbaum Associates, p. 480.
13. As the author of an eight-word
response to the same Spector article reprinted in the April 15th, 2015 edition of The Guardian put
it, “Science has gone flipping mad these days, unbelievable.” See
the comment by “Thompson1001.”
The Gene Illusion: I bring a critical perspective to claims in the media
and the scientific literature that genetic factors underlie psychiatric
disorders. My new book, “The Trouble with Twin Studies: A Reassessment
of Twin Research in the Social and Behavioral Sciences,” is available from Routledge.
Thank You Dr. Joseph and MIA.
The next time your political blowhards sound off about 'Mental
Health' funding, mail them this post.
So long as Governments keep laying out bowls full of OPM for
this stuff there will never be any shortage of 'researchers' coming around to
feed on it.
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