58 PRETEND GENESmea sures like IQ than DZ pairs. In other words, the twin method is unfi t
for purpose.
So how can twin researchers possibly continue to claim that they have
a valid method for separating the eff ects of genes and environments? How
can the Plomin team, for example, continue to argue that “the equal
environments assumption has been tested in several ways and appears
reasonable for most traits”?^24
Sarah Norgate and I took quite a hard look at these so- called tests and
reported fi ndings in a paper in the British Journal of Educational Psy chol-
ogy.^25 Th ese tests are blighted with the make-do empirical culture that
pervades this whole area of research. Th ey are not carefully controlled
studies based on clear knowledge of relevant environments. Th ey simply
attempt to see whether diff erences in physical appearance, as reported by
parents in questionnaires, and assumed to refl ect how similarly twins will
have been treated, correlate with diff erences in IQ or school test scores.
Th e studies suff er also from selective reporting of results and of inappro-
priate statistics.
Attempts to justify the EEA have continued with further indirect,
oft en contorted ploys. Th e latest is that of Dalton Conley and colleagues
published in the journal B e h a v i o r G e n e t i c s in 2014.^26 To me the correla-
tions look more like a scatterplot than a coherent pattern. Indeed, the
authors acknowledge in vari ous places the weakness of the data (espe-
cially the low numbers of participants) for reliable comparisons. But
they conclude that the EEA is supported and the twin method is ro-
bust anyway. More fundamentally, similarity of environments as such
was not— and could not possibly have been— directly mea sured, and
here is why.
We Do Not Know What the Relevant Environments Are
To test the EEA, we need to be clear about the environments specifi cally
relevant for creating diff erences/resemblances in the trait in question
(e.g., IQ, education). Anything else is just guesswork. Of course, there is
much guesswork about what is really being mea sured in IQ or other sup-
posed tests of potential, anyway. But recall Th omas Bouchard’s statement,
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