"The claim I'm making is girls and boys are different- that image strongly supports that claim," he said.
Sax noted in his Psychology Today article that academics such as Judith Butler have pioneered popular theories that "male" and "female" are merely social constructs.
"The category of 'girl' and 'boy' are meaningful categories, they're not a mere performance or a social construction as Judith Butler would have us believe. And they are clearly meaningful and real prior to birth," he said.
Sax also pointed out that The New York Times published an op-ed April 1 in which Dr. Carol Hay, a professor of philosophy at the University of Massachusetts-Lowell, endorses Butler's understanding of gender, calling gender "fundamentally a performance" based on and learned from social systems.
Sax posited that the author is unaware of "research showing that 'male and female' are present in the human brain prior to birth."
"I wouldn't say that she is lying, I would say that she is unaware of the relevant research," he clarified.
CNA reached out to Hay for a reply. She told CNA in an interview that when it comes to gender, she tends "to be pretty critical of the science, because I think it's often motivated by a particular political agenda, as all science is motivated by a particular political agenda."
Despite this, Hay said that in her view, even if science can prove that there are innate biological differences in the male and female brains, "I'm not sure that would tell us anything about why boys and girls end up acting completely differently."
"The question is whether those brain differences- if they do exist- the question is whether they then actually translate into the kind of gender differences that we're used to associating with men and women and boys and girls," she argued.
Sax, however, maintained that the data is meaningful, showing a concrete difference in brain function between males and females, even if it is not yet clear what that signifies.
"That claim that gender is meaningless, or gender as merely a 'performance' isn't a true statement. It's a false statement," he said.
(Story continues below)
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Jonah McKeown is a staff writer and podcast producer for Catholic News Agency. He holds a Master’s Degree from the University of Missouri School of Journalism and has worked as a writer, as a producer for public radio, and as a videographer. He is based in St. Louis.