It has long been an accepted mantra that men are from Mars and women are from Venus. But, if you look at the overall structure of the brain, those of both sexes are generally the same, a new study suggests.Although specific parts show sex differences, an individual brain only rarely has all "male" traits or all "female" traits, researchers say.The human brain is usually a mixture of the two, with some aspects more common in women, some more common in men, and some common to both. This contradicts the idea that brains can be neatly divided into two sex-based categories, the authors of the research say.Daphna Joel, of the School of Psychological Sciences, and the Sagol School of Neuroscience at Tel Aviv University, said: "It is a very popular belief, even among scientists, that brains have a male and female form. What we were interested in is looking at the entire brain."Even if there are differences, does it mean brains come in two different forms?"Their research, published in the Proceedings of the National Academy of Sciences, involved taking MRI scans of more than 1400 brains, focusing on anatomy more than how brains work.They analysed brain features such as tissue thickness and the volumes of different parts of the brain. They focused on traits that showed the biggest sex differences, dividing the scores into a predominantly male zone, a predominantly female zone, and an intermediate range.Researchers found that it was rare for brains to fall into one of these three distinct categories - only 6% of the brains they examined could be placed in one particular group. It was far more common for an individual brain to score in both the male and female zones.The researchers used a similar approach to analyse psychological and behavioural scores from two prior studies that covered more than 5000 participants, and again they had similar results.Overall, the results show that "human brains do not belong to one of two distinct categories", male and female, the researchers concluded.Larry Cahill, a neuroscientist at the University of California, Irvine, who did not participate in the new study, said he agreed that brains contain various combinations of male and female anatomical traits.But that does not rule out differences in how the brains of the two sexes work, he said.There is "a mountain of evidence proving the importance of sex influences at all levels of mammalian brain functioning", he said, adding that evidence shows that sex does matter "even when we are not clear exactly how".In the past, scientists have suggested that gender differences emerge only through environmental factors and are not innate.Neuroscientist Gina Rippon, of Aston University, Birmingham, has said that any differences in brain circuitry come about only through the "drip, drip, drip" of gender stereotyping...