What are you basing this statement on?
Well I actually first learned this in college in a child development class, but here's something else:
Physiologic imaging
The ability to evaluate the form and function of the human mind has undergone almost exponential growth and a paradigm shift in recent years. Magnetic resonance imaging, for example, is now being used to analyze physiology in addition to anatomy. Using diffusion tensor sequences on MRI machines, the rate that molecules diffuse in and out of a specific area of tissue, directionality or anisotropy, and rates of metabolism can be measured. These sequences have found consistent sex differences in human corpus callosal morphology and microstructure.[which?][15][16][17]
Morphometric analysis has also been used to study specific 3-dimensional mathematical relationships with MRIs, and have found consistent and statistically significant differences across genders.[18][19] Specific algorithms have found significant gender differences in over 70% of cases in one review.[20]
Research has been done on the shape of the corpus callosum in those with gender identity disorder. Researchers were able to demonstrate that the shape dimorphism of the corpus callosum at birth in biological males who self-identified as female was actually reversed, and that the same held true for biological females who self-identified as male. The publishers of this article argued that the shape of the corpus callosum defined the mental sex of individuals over their physical sex.[20]
The relationship between the corpus callosum and gender remains an active subject of debate in the scientific and lay community.
The part about war is my own speculation, though I'm clearly not the only person to think it. It would give men strength in being able to detach, so that they could go away to hunt or fight (most women used to stay in tribal villages together, with children, while most men either hunted or fought off other tribes) ...however, this gave women strengths that men don't have, because the two hemispheres are more connected.
My other point in response to fia is that if women are more likely to do xyz out of feeling or emotion, men are still more likely to be sociopaths, narcissists, murderers...
So if we say women are more likely to be feeling types, or even that they are more emotional in a particular way from hormones, this does not in any sense of the word make them less rational than men, who apparently are much more inclined than women toward committing violent crimes and lacking empathy...neither of those things are rational. I am of the opinion most sociopaths need to be put to sleep, and I think the death penalty needs to be kept alive to service that societal need.
However, there are a very small number of women sociopaths (very small, over 90% are men) and of course there is the occasional woman who actually wants to go into combat.
This also isn't to say that ALL men are narcissists or sociopaths, nor is it to say that ALL women are more sensitive emotionally, even to the point of being out of control and harming others.
Which is why I say men and women are equally irrational, just in different ways. Also, anyone who devalues women for having these differences clearly aren't valuing the fact that women tend to see things more holistically than men because of the two sides of the brain being more connected, which means that they understand things that a lot of men might not.
Though of course there are men who have this ability too.
I think this may be the reason why women are slightly more likely to be Pe doms or Ps, Fs instead of Ts, and Es instead of Is. The Pe/P preference points to holistic thinking, both Se and Ne see the "big picture" just in different ways.