extension is not warranted given the recent spate of stud-
ies that are all converging on 77 to 93 percent classifica-
tion accuracy based on whole brain data—including a
more recent study led by Joel! What’s more, the method
that Joel and her colleagues devised for quantifying
“internal consistency” in their earlier article is a straw
man guaranteed to always find very low levels of consis-
tency. By defining “consistency” as 100 percent uniformi-
ty, there is no way that their method will ever detect con-
sistency as long as there is some variation within each
sex. Del Giudice and his colleagues have shown this to be
the case with artificial data and illustrated it by showing
that the method cannot even detect consistency within
species (they compared the facial anatomy of different
species of monkeys). More realistic than having 100 per-
cent consistency, in my view, is whether the pattern is sta-
tistically robust—whether you can distinguish between
men and women with a very high degree of accuracy
based on aggregate patterns of interests. And this is why
their initial finding is such a red herring: their conclusion
is not based on whole brain data. To dive deeper into the
critique of the study by Joel and her colleagues, I recom-
mend reading this and this.
(^8) I intentionally separated out “genetic” from “biological”
in this sentence because it’s a common misconception that
“biological” equates to “genetic.” The question “Are sex dif-
ferences biological or cultural?” is actually a meaningless
question because every sex difference is biological when
it’s expressed, regardless of whether its origins are cultural
or genetic. Social-learning processes are biological. Aspects
of personality that are learned are also biological. In fact,
anything that affects behavior is acting biologically on the
brain. When people say traits or sex differences are “bio-
logical,” they probably really mean “genetic.”