The way I see it is that, as often when it comes to differences due to sex, you have two wide Gaussian distributions that overlap a lot. Sure, there are behavioral differences (due to testosterone or other reasons), but the variation in behavior within one sex is probably larger than the distance between the means.

The problem is, that in casual speech, we can only easily express black-and-white: either men and women are different due to testosterone, or they are not. Neither statement is really correct.

With mental rotation, there is practically no overlap. See the graph from the original study.[1]

It's a similar story for physical strength. Nobody denies that men tend to be stronger than women, but most people vastly underestimate the disparity. In a study that measured grip strength in 2,000 people[2], the weakest 5% of men were comparable to the top decile of women. Even elite female athletes were only as strong as the median untrained male.

There are more examples (propensity for violence is another big one), but it takes time to find citations. Suffice it to say that most people think the sexes are more similar than they actually are.

1. https://brothersdiamond.files.wordpress.com/2015/02/menwoman... (For more on mental rotation and testosterone's effects, see my comment downthread: https://news.ycombinator.com/item?id=10443021)

2. http://egitim.judo.gov.tr/Dosyalar/makaleler/-ENG-Hand-grip-...

There's plenty of studies that debunk the mental rotation myth:

http://www.sciencedaily.com/releases/2010/09/100915080431.ht...

http://www.researchgate.net/profile/Angelica_Moe/publication...

There's also a study showing the field of neuroscience having a tendency to make unsupported and untested claims to confirm stereotypes http://link.springer.com/article/10.1007%2Fs12152-012-9169-1

http://www.northwestern.edu/newscenter/stories/2015/08/scien... Is this also stereotypical? Read what the researcher(a woman by the way)had to say. For 20 years, she actively avoided studying sex differences in the brain until her own data showed her that differences between females and males were real. Let science be about cold-hard facts and let it not be muddied by "feelings".

there's a pretty big difference between "debunk[ing] the ... myth" and showing the effect is real and can be reduced via training. in particular, your second link says the differences are probably real in its conclusion!

The myth is that the differences (in mental rotation ability) are innate or "biological", not that there is differences (in mental rotation ability) in the first place.

If one gender displays innate ability and the other can be trained to match it, then the difference is not shown to be a myth. There is a very dishonest redefinition of a common word involved to make the meaning apply.

Political fictions are comfortable but don't really change facts, they just color interpretations. Mischaracterizing observation does not serve to make an argument appear stronger.

Note that none of this means women are inferior, and if you are construing my point to mean I am arguing for that position, you have imposed that on me.

>> myth is that the differences are innate or "biological"

erm...please read

1. Genomic differences between developing male and female brains in the womb-- http://www.sciencedaily.com/releases/2015/02/150203190223.ht...

and if you still feel that somehow humans try to gender stereotype whilst the fetus are still in the wombs, then read this also-

2.Sex differences in rhesus monkey toy preferences parallel those of children-- http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2583786/

I was referring to mental rotation ability, I clarified it in an edit.

I also don't have time to go into the studies you linked about general differences but similar studies have been debunked before. For example with 1.5 day old infants where the experimenters knew about the sex and their bias subtly corrupted the experiment and it did not reproduce when the bias was truly accounted for.

Often people want things to be 'equal', and often they don't really think about where that equality applies and what it really represents. I suspect many of them only want fairness but the inability to articulate that means they contort many statements into metaphysical absurdities to avoid having to be empathetic.

There are definitely differences in both generic mental abilities and what fields interest people between the sexes. From an evolutionary biology perspective, it would be really weird if there weren't.

To be clear, men and women are equally mentally gifted as a whole, but focused on different skills, and with bigger variance in men.

Pinker's "Blank Slate" lays out the case well: http://www.amazon.com/The-Blank-Slate-Modern-Denial/dp/15012...

You mean evolutionary psychology, not biology. The former is basically a pseudoscience and the latter makes no such claims.

I'm not even saying this is an established scientific claim, only that it would be really weird if the statistical differences between men and women were 100% outside of the brain, given how different the evolutionary pressures are.

Evolutionary psychology does have some problems :) It's easy to tell dazzling and believable stories in that frame, but much harder to prove them empirically.

I think some real science is being done in the field, but I agree that when people make EP arguments on the internet, you need to apply a lot of skepticism.

I've understood that while men are better at spatial reasoning, they are barely statistically better. And while women are better at language tasks, they are way better. So the conversation has always been slanted in that way.

Did your colleague know about mental rotation tests?[1] Men perform significantly better than women at these. And among men, mental rotation ability is correlated with testosterone levels.[2] I could see your buddy arguing that culture was responsible for behavioral differences such as violent tendencies, but the same dismissal can't be made of this test.

1. https://en.wikipedia.org/wiki/Mental_rotation

2. http://www.academia.edu/3118000/The_relationship_of_male_tes...

As esailija posted elsewhere in this thread, at least one study has shown that gender differences in mental rotation tasks can be eliminated through training.

In the "soft" sciences, about 1/3 of all studies get the wrong result.

This means you can always find a study supporting what you want to believe.

>Men perform significantly better

Actually, the reference you cited says "slightly better". It may or may not be significant but let's stay on track here.

In the original mental rotation test, there was no overlap between men and women: https://brothersdiamond.files.wordpress.com/2015/02/menwoman...

The Vandenberg and Kuse paper[1] followed up on this using a test that was easier to administer to large groups. In that study, the average male score was the same as the 85th percentile of female scores.

"Significant" describes this difference much more accurately than "slight."

1. http://wexler.free.fr/library/files/peters%20(1995)%20a%20re...

The male versus female is amazing, but what about that drop in ability from age 29 to 33. I know one of the video game FPS coaches said that after you turn 30, one is out of the game, but look at that drop. There should be studies to figure out what causes that; it is impacting male and female.

The drop is probably multiple factors, including aging. The study was done in 1975. Someone 28 years old would have been born in 1947. A 33 year-old would have been born in 1942 –the darkest days of WWII. Prenatal nutrition was likely an issue then. Ditto for those born earlier, as they had to deal with the great depression.

Also, the sample size in the first study was rather small, as they were just trying to answer the question, "Does the time it takes to mentally rotate an object depend on the angle of rotation?" (Answer: yes.)

> The desire to believe in equality is weird sometimes.

It's not that weird. If you look back in the HN archives, you can find one or two submissions from transsexual authors who argue, essentially, that after changing genders, they were discriminated against more, and that this proves that society/Silicon Valley/etc must be extremely sexist & discriminatory because nothing else about them changed; many of the HN commenters agreed with the claims.

>I had a (male) colleague once argue with me that men and women had no differences in mentality due to testosterone. The desire to believe in equality is weird sometimes.

Not to mention that there are lots of other differences that can have an impact, from the generally reduced physical strength, to birth related effects all the way down to increased life span...