A short exchange on ABC radio on Monday neatly demonstrated the point: Men have a natural pre- occupation with sex.

Alex Sloan was trying to explain to colleague Ross Solly how typically male he is. ”But it’s OK, you’ve got bigger parts, Ross,” Sloan said. He seemed chuffed.

She was talking about the male brain. He – we can only assume – was thinking about sex. And that’s how it is at the crossroads of gender thinking: the same stimulus, but as men and women we head in different directions.

In fact, if you’re to believe American neuro-psychiatrist Dr Louann Brizendine, not only do men have 212 times the brain space devoted to sexual drive, but their ”hub” for processing sexual thoughts can be likened to the size and activity of an airport, compared with women’s smaller ”airfield nearby that lands small and private planes”. However, when it comes to detecting, processing and understanding emotion, women’s brains dart off on a ”superhighway” of connecting routes, while men potter down a lone ”country road”.

But we all know that. We know it intuitively and we know it anecdotally.

Now – thanks to very recent advances in genetics and brain imaging technology – Brizendine says we should also know and understand it scientifically.

In her book The Female Brain, published in Australia this week, Brizendine takes a firm scientific position against the idea of the ”unisex brain”. There is no such thing, she says. Instead, she argues that while 99 per cent of genetic coding is exactly the same in males and females, it’s that less than 1 per cent, that is gender-specific, which accounts for the major differences in how men and women behave and relate to the world.

Brizendine’s area of expertise is hormones, and her research has focused on the ”massive neurological effects” that fluctuating hormones have on women at the different stages of their lives.

In a nutshell, Brizendine’s call is for us all to accept that men and women’s brains are chemically and architecturally different – that we are hard-wired differently. And, yes, it does have a lot to do with size.

While the brain’s sexual processors are bigger in men than women, the principle hub of emotion and memory formation is bigger in women than men; as is the brain’s centre for language and hearing. But then the areas of the brain which register fear and trigger aggression are – unsurprisingly – bigger in men than women.

Again, much of this information can be met with a kind of knowing smile. We all know it. It comes as no real surprise too that one of Brizendine’s studies showed how, when viewing emotional images, brain scans found nine areas light up in a woman’s brain and only two in a man’s.

Nor is it surprising to learn that the area in the brain that is responsive to anxiety is more developed in women than men.

Or that men pick up subtle signs of sadness in a female face only 40 per cent of the time, whereas women pick up signs of sadness 90 per cent of the time. And as for women and their ”gut feelings”, Brizendine explains that these so-called feelings are in fact responses to real physical sensations in the body, and that a woman’s brain has more cells to detect bodily sensations than a man’s.

So, is this just science finally supporting what we all know and have long suspected anyway?

And if so, why is Brizendine the arch enemy of American feminists?

Professor Janet Hyde, head of women’s studies at the University of Wisconsin-Madison told Newsweek that she was ”disgusted” by scientists like Brizendine who ”exploit trivial differences between the genders”. Brizendine’s book, she said, is ”bad for my blood pressure”.

Another, Dr Nancy Andreasen, a psychiatrist and neuroimaging expert, also railed at Brizendine for raising the issue of biology and ”nature”, ignoring the powerful affects of nurture and social conditioning.

”Whatever measurable differences exist in the brain,”an angry Andreasen said, ”are used to oppress and suppress women.”

It’s the old ”don’t mention the biology” line, from hardline feminists who are terrified that women’s biology will dictate their destiny – that is, we will all head down the path of the mindless breeding machine.

This week in defending The Female Brain, Brizendine explained on ABC radio that she has long been torn between politics and science. In the end, science won. ”I have chosen to emphasise scientific truth over political correctness,” she said.

Right then a chorus of women leapt into the air, shouting, ”Yes! You go girl!”

Well, perhaps they didn’t leap, but plenty of women certainly cheered her on. Not because we want to use gender differences to highlight negatives – but rather to make claim on some positives.

Acknowledging hard-wired physical, chemical and hormonal differences in male and female brains is in fact liberating for women. Ever since the dawn of second-wave feminism in the late 1960s and early ’70s, women have been compelled to ”fit in” to a male world that orientates around male rhythms. Frantic efforts to mirror men and prove our ”sameness” has seen women try to morph into men, rather than claim an equal right to be women.

Some grumpy old feminists might still be afraid of acknowledging gender differences, but younger, less threatened feminists want to celebrate it.

Brizendine concludes The Female Brain by saying, ”We are living in the midst of a revolution in consciousness about women’s biological reality that will transform human society.”

She says she can’t predict the nature of that change. I say never mind just bring it on!