"Long before it's in the papers"
December 03, 2015


No definite structural difference between male, female brains, study says

Dec. 3, 2015
Courtesy of PNAS
and World Science staff

Al­though male and female brains tend to be dif­fer­ent, no sin­gle struc­tur­al fea­ture clearly dis­tin­guishes them, sci­en­tists have con­clud­ed in a new stu­dy.

The way it seems to work, they say, is like this: “most brains are com­prised of un­ique ‘mo­saics’ of fea­tures, some more com­mon in fe­males com­pared with ma­les, some more com­mon in males com­pared with fe­ma­les, and some com­mon in both fe­males and ma­les.”

The state­ment come from a pa­per pub­lished in this week’s edi­tion of the jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces.

To reach the find­ings, re­search­ers stud­ied more than 1,400 brain scans cap­tured us­ing Mag­net­ic Res­o­nance Im­ag­ing, or MRI. The tech­nol­o­gy uses mag­net­ic fields and ra­di­o waves to cre­ate de­tailed im­ages of the or­gans and tis­sues. The brain scans fell into four sub­groups or “data sets” de­pend­ing on the pre­cise MRI meth­od­ol­ogy used.

For each data set, the authors ident­ified brain re­gions that diff­ered the most be­tween the sexes. For each brain, then, they checked wheth­er the shape of each re­gion was on the end of the dis­tri­bu­tion where fe­males were more prev­a­lent (“fema­le-end”) or at the end where males were more prev­a­lent (“ma­le-end”). 

De­pend­ing on the set of MRI da­ta ex­am­ined, be­tween 23 per­cent and 53 per­cent of brains had at least one re­gion with a “ma­le-end” score and one re­gion with a “fema­le-end” score, the in­ves­ti­ga­tors said. In con­trast, the per­cent­age of brains with all “ma­le-end” or all “fema­le-end” scores was 8 per­cent or less.

“Our study demon­strates that, al­though there are sex/­gen­der dif­fer­ences in the brain, hu­man brains do not be­long to one of two dis­tinct cat­e­gories: male brain/female brain,” wrote the re­search­ers, with Tel Aviv Un­ivers­ity in Is­ra­el, the Max Planck In­sti­tute for Hu­man Cog­ni­tive and Brain Sci­ences in Leip­zig, Ger­ma­ny and the Un­ivers­ity of Zu­rich in Switz­er­land.

“These find­ings,” they added, “are cor­rob­o­rat­ed by a si­m­i­lar anal­y­sis of per­son­al­ity traits, at­ti­tudes, in­ter­ests, and be­hav­iors of more than 5,500 in­di­vid­u­als, which re­veals that in­ter­nal con­sist­en­cy is ex­tremely rare.”

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Although the brains of males and females tend to be different, no single structural feature clearly distinguishes a “male” from a “female” brain, scientists have concluded in a new study. The way it seems to work, they say, is like this: “most brains are comprised of unique ‘mosaics’ of features, some more common in females compared with males, some more common in males compared with females, and some common in both females and males.” The statement come from a paper published in this week’s edition of the journal pnas. To reach the findings, researchers studied more than 1,400 brain scans captured using Magnetic Resonance Imaging, or MRI. The technology uses magnetic fields and radio waves to create detailed images of the organs and tissues. For each brain, the scientists determined whether the form of each region was on the end of the distribution where females were more prevalent than males (“female-end”) or at the end where males were more prevalent than females (“male-end”). Depending on the set of MRI data examined, between 23% and 53% of brains had at least one region with a “male-end” score and one region with a “female-end” score, the investigators said. In contrast, the percentage of brains with all “male-end” or all “female-end” scores was between 8% or less. “Our study demonstrates that, although there are sex/gender differences in the brain, human brains do not belong to one of two distinct categories: male brain/female brain,” wrote the researchers, with Tel Aviv University in Israel, the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany and the University of Zurich in Switzerland “These findings,” they added, “are corroborated by a similar analysis of personality traits, attitudes, interests, and behaviors of more than 5, 500 individuals, which reveals that internal consistency is extremely rare.” study said