How accurately do humans identify biological sex?

Why would like sort of research be more complex than other similar types of research? I'm sure there are lots of variables but that doesn't usually prevent research entirely. I'm no expert though.

You know how scientists have been trying to decipher dolphin speech for years? It turns out that 95% of the speech content is discussion about pronouns. I mean, come on, how can one dolphin figure out the sex of another one, they all look practically the same!

When I walk alone after dark I'm constantly on the alert for potential threats. Not paranoid, just a woman who has been attacked by male strangers on more than one occasion; sadly, this is pretty standard if you talk to your average female. And I can tell from a great distance if someone is male - their height, shape, gait, body language. It feels encoded but probably also from accumulated vigilance and risk assessment. I'm pretty sure this is quite common.

not sure scientific studies are needed

They are absolutely needed as there is money to be made from technical applications of machine learning ie identification of individuals

I'm pretty crap at remembering faces, following directions, etc. But even I have only inadvertently "misgendered" someone twice. They were:
A) a prepubescent boy with long hair
B) a woman dressed as a jellyfish.

Animals that don't have sexual dimorphism have other, non visual clues to determine biological sex. Such as scent or behaviour.

Humans are sexually dimorphic, and adult males and females look different. Even animals can spot the difference, they don't have to rely on their sense of smell to work out what sex humans are.
Its such a fundamental social signal that people get confused and angry when they feel they have been hoodwinked or fooled.

Children don't look different because they take a long time to mature, and it would not be in their best interests - they are not sexually available.

But what's teh point?

Poeple keep saying that sex is a social construct. Gender is real. There are no such thing as sexed bodies. You can't tell teh difference between men and women nearly as well as you think...

It's not true though is it. Clearly sexed bodies exist and wihtout the trappings eg hair makeup clothes - clearly it's pretty obvious which are male and female due to the whole cock / cunt thing.

As a PP said though, pre-puberty it is quite hard to tell if a child is male or female without stereotypical visual cues.

It would be interesting to know how good humans are at correctly guessing sex with trans people who have been on puberty blockers and then cross sex hormones, who them become adults who have not gone through puberty.

Body shape is the big one, very difficult to change that, esp if the narrow hip and long torso, just ain't nothing going to hide that. But there are other tells, like adam's apple (unless they had that surgery), and other things like the brow line, and sometimes even the shape of the clavicle (women don't have the real V shape, but alas some males can have the wide, flat one).

But all in all, late transitioners, rarely ever pass.

I won't say you can tell 100% of the time, but you can tell a lot of the time. And some people are super androgynous, regardless.

I find the inter-species thing really interesting. When my cat was a few months old, she started following my prepubescent son everywhere and doing this strange thing with her tail. (I'd never seen a cat in heat before.) I took her to the vet, who said that cats in heat seek attention from male humans if they have no access to a tom. It seems to be a scent thing. I'm sure cats have a better sense of smell than humans but I still think I can distinguish between an adult woman and an adult man by smell. Or maybe I identify as a cat.

I think we notice it the same way you can sense someone is gay (I hate the term gaydar but that's basically what but is) when you first see them.
I tried a google search on the op's question and totally disappeared down a rabbit hole in that august journal The Scientific American-some dingbat did a 'study' on gaydar that showed a higher than statistically predicted ability to gaydar. How much higher we weren't told, the sample size was small, no test for standard deviation(yawn) and the article quoted the Urban Dictionary ffs! It was seriously homophobic. And gay chaps you're next-you've been warned. The 'scientist' wrote this book. screenshots.firefox.com/blxVnn1MzSTOF0yG/www.goodreads.com Explains alot.

Animals that reproduce sexually have to have a way of recognising the opposite sex - for maximum efficiency of passing on genes.

Whilst there is probably some kind of normal distribution of these features but in general adult males are taller and have bigger feet and hands, a bigger musculature, have narrower hips and wider shoulders. Closer up facially they have wider jaws and a more pronounced eyebrow ridge probounced Adam’s apple and obvious facial hair growth even if shaved.
Any trans women who “pass” have usually had facial surgery of some kind and even then they can’t disguise their height, their feet, hands broad shoulders etc.

PermissionTo Speak -

Yes that is interesting. Like that guy on Big Brother when he came out with his woman-stuff on, the men were all agog.

I think this is a result of men (well all of us) being fed an idea of women as sexual objects with XYZ "triggers" which are nothing to do with being male or female - the accoutrements. Big hair, lots of makeup, short skirt. Lingerie. Certain poses. We are all constantly fed images of "sexy lady" which if copied by a man well enough, and he has a face and body that are not too overtly masculine in the first place, will trigger this response. The trigger things + not really seeing women as people but as a selection of body parts - hair, tits, arse. It's a consequence of extreme dehumanisation and sexualisation.

Clearly it wouldn't work if the men and women were all naked / or even dressed in neutral clothes with no makeup. And talking :D

I also think the cases of people being 'fooled' is by the duper understanding the psychology and responses of the duped through being the same sex - they know how to push their buttons in the way the opposite sex usually doesn't.

I have over the years successfully managed to only pull people who had a dick not a cunt when I got them home. Like 100% accurate, never made a mistake.

Same here, but I do know blokes that are so thick, with such crude, inaccurate responses that they have been fooled by transvestites.

One such male I know said it was a dream seduction - not a word spoken - and when the bloke open his mouth and a blokes voice and "Hi I'm Bloke''s Name" popped out, all he felt was crushing disappointment. I think this ludicrous, crass inaccurate aspect of some men''s sexuality is why they are fooled or believe they pass.

DH says the response to certain triggers can be so powerful that it is not inconceivable for a bloke to be turned on by a crude mouth drawn on paper with red lipstick and crude eyes drawn with mascara to bring out that response, if make up is a bloke''s thing.

I think you've got two things going on here, firstly the prefrontal cortex brain, which looks at someone and works out they are male, female or is not sure based on fairly superficial characteristics, and secondly the limbic/ emotional bit of the brain, which is making much faster judgements that are not, at least initially, conscious. This may include is this person a threat, or am I attracted to this person, which may be sex specific. This will pick up on how someone moves, expresses themselves, talks etc. As humans we are constantly scanning our environment for threats women we are socialised through our direct experience and what we are told to recognise that (some) men are threatening to us, so I'd say in most cases we recognise it pretty quickly.

There are many articles on google scholar. Facial recognition is an important area not just for general interest, but for the police, border control, building security. This is of course to teach machines, but there are areas of overlap in the research because of course human and machine are detecting the same differences. Whatever use its put to research needs to include sex and age and race data to make it more accurate. Plastic surgeons would also use the information to help their trans clients.

I have read a few studies when I've clicked through from conversations I've seen/been involved with on social media but I'm afraid I haven't saved any to provide links. The person to ask is that Logical Marcus fellow on Twitter.

The pretence that human beings generally don;t know and can't tell what sex other human beings are is laughable.

Mammals can tell what sex others of their species are - it's pretty key. Humans knew that there were males and females and which was which before we had language. And no of course I can't prove that, but it's just totally fucking obvious.

Anecdotally - I would say quite well.

I am hetersexual in the old fashioned sense that I like the sort of body you find on a penis-person (generic) and in fact am quite keen on the acual penis when enjoying a sexual interaction.

I have over the years successfully managed to only pull people who had a dick not a cunt when I got them home. Like 100% accurate, never made a mistake .

With my husband, I was even more certain, as after some of our sexual interactions my tummy got big and then some time later a baby came out. This, I believe, is quite a strong pointer that as a woman, you've been fucking a man.

It’s been a while since I did developmental psych, but from what I can recall from birth babies can recognise and distinguish faces. They can also distinguish by sex. If a baby’s primary care giver is female, the baby will prefer strange female faces over strange male faces. Older children (like 5 to 7) are not good at recognising the sex of other children (when all stereotypical cues are taken away), but they are very good at identifying male and female adult faces. It seems that our basic face recognition ability (knowing that something is a face) is innate- we are born with it. What kind of faces we recognise, however, may be learned. For instance, there’s a period where babies are very good at distinguishing monkey faces (human adults can’t do this). If the babies are regularly trained to recognise monkey faces, they keep that ability for life. If they aren’t trained, they lose it at one year. But in short, our brains are exceptionally good at recognising and distinguishing sexed faces from a young age.

I have read that human infants start to be able to distinguish between male and female faces (and have a preference for female faces, especially their mothers) at about 3-4 months of age. Don’t have a link though.

It's the little incongruities that you notice, the size of their knuckles, the slenderness of a wrist, the shape of hips, or size of feet.

I think we notice it the same way you can sense someone is gay (I hate the term gaydar but that's basically what but is) when you first see them.

Not all people are observant as others, and some people don't pick up on it, but I think most people do.

I'm not sure scientific studies are needed. It'd be one of those "Oh look scientists have discovered that humans need water" moments.