Women are spiritually tougher than men

Male brain ≠ female brain

Men have bigger brains than women, and that's not the only difference. But those who jump to conclusions from this have to be prepared for contradiction.

Men can park better and act more goal-oriented. Women are more empathetic and can talk better about their feelings. Such clichés are widespread. The differences are often explained with evolution, with genes and hormones. Undoubtedly, these play an important role. They influence our behavior and brain development. But is there also such a thing as the female and the male brain?

For decades, neuroscientists have been looking for gender-specific peculiarities in the structure and function of the brain. And you will find what you are looking for. However, it turns out to be far more difficult to interpret the results. Do small differences in structure or function affect our behavior? Or is it the result of a gender-specific upbringing? Or is it something completely different? It is not uncommon for researchers to get into quarreling over such questions.

Networked in different ways

For example, a study in 2014 led by Ragini Verma showed that the brains of female and male adolescents are networked differently. Using what is known as diffusion tensor imaging (DTI), the researchers examined the course of the nerve fibers in 950 male and female test subjects aged 8 to 22 years. They found that male brains are more interconnected within the two hemispheres of the brain with the onset of adolescence. In women, on the other hand, there were more connections between the left and right hemispheres of the brain.

The study received a lot of media attention and was used as an explanation for all possible gender-specific differences, for example that women are better at multitasking and men are more focused.

"It's all nonsense," says Lutz Jäncke, Professor of Neuropsychology at the University of Zurich. Firstly, women are not better at multitasking or men at goal-oriented thinking - in general, men and women are very similar in their behavior and performance. Only a few tests, such as spatial reasoning, would do men and women with certain linguistic abilities slightly better. Second, the difference in networking is not a gender-specific feature at all, but rather due to the size of the brain.

The size is what matters

It is undisputed that men have bigger brains than women. An average male brain measures around 1.4 liters and a female brain a good 1.2 liters. In most studies that looked for differences in subregions of the brain, this is not taken into account when interpreting the data, says Jäncke. Following Verma's study in 2015, he and his colleague Jürgen Hänggi showed that the difference in networking disappeared when they compared the brains of the same size in men and women.

Accordingly, not female and male brains are networked differently, but large and small. This finding was recently confirmed by another group. Jäncke justifies the different networking with a thesis that the brain researcher James Ringo put forward more than 20 years ago. He explained that because of the greater distance between the hemispheres, large brains have to establish longer connections than smaller ones. But because longer lines are less efficient, larger brains connect more regionally, i.e. within a hemisphere. According to the thesis, this means that the two halves of the brain work more independently of one another in large brains than in small brains.

What the different networking of large and small brains means for their performance remains unclear. Big brains work differently than small ones, says Jäncke. In any case, big brains are no better than small ones. Otherwise men would have to be more intelligent than women, and that is not the case. How the size difference in the brain comes about, however, is unclear. Apparently it has little to do with body size, because it does not correlate well with brain size, as Jäncke and colleagues showed in 1998.

Some differences remain

However, not all differences in the brains of men and women can be explained by the different total volume. At the beginning of the year, for example, a study with over 5000 participants led by Stuart Ritchie from the University of Edinburgh showed that men have a greater volume of the cerebral cortex than women and that many subcortical regions, such as the hippocampus (memory formation, spatial orientation) , the amygdala (emotions and physical excitement) or the striatum (reward and learning) are larger in men. In women, the cerebral cortex was thicker, despite the smaller volume, and the network of nerve cells (white matter) more complex.

The differences partially disappeared when the researchers took the brain size into account. However, 14 of a total of 68 regions of the men's cerebral cortex still had a larger volume. After the "size correction", however, 10 regions in the cerebral cortex of women were larger than that of men. The study has not yet been published, but has appeared unedited on the BioRxiv server. However, the results coincide with those from earlier publications. The differences after the "size correction" are small in each case, but they do exist.

In contrast to Jäncke, Ritchie argues that there is no point in calculating the size from the data. Because it is a fact that men have bigger brains. That is the biggest gender difference. Whether and how this affects behavior or certain performance needs to be examined more closely in future studies.

Similar to the social scientists, there are also among brain researchers those who uphold the similarities between the sexes and those who emphasize the differences. The latter like to argue that even minimal differences could be medically relevant. Because there is a possibility that one therefore has to develop gender-specific therapies for mental illnesses such as depression, addictions, schizophrenia or post-traumatic stress disorder, explained Larry Cahill of the University of California, Irvine, in an article. These diseases occur differently in men and women, or they take different courses.

Male and female at the same time

Other researchers, however, find that this categorization is neither helpful in the case of mental illness nor anything else about the individual. Most of all, Daphna Joel of Tel Aviv University doubts that there is a categorical difference between male and female brains. Rather, the brains of men and women consist of a mosaic of male and female parts - just as there are men who have "female sides" and are, for example, empathetic or can talk about feelings, and women who have skills that are considered male such as a good spatial imagination or rational action.

Joel justified her thesis in a 2015 study. In it, she and her colleagues, including Jäncke and Hänggi from the University of Zurich, compared the brains of 1,400 men and women and focused on ten regions that differ greatly between the sexes. Based on their size, they determined how male or female they were.

The analysis found that most people have both female and male and many intermediate regions. In general, most women had more female regions and most men more male regions. But hardly any person had only male or only female regions, all of them showed a kind of mosaic. So you can't make a clear distinction and speak of a female or male brain, Joel concluded.

Opposition arose immediately. Marek Glezerman from Tel Aviv University replied in a comment: "Yes, there is a female and a male brain." It only depends on the level that one is looking at. Even if the differences in the rough structure are small, each individual nerve cell is female or male due to its chromosomes.

In addition, it is not just a matter of anatomy, but also of function. If you just look at the structure - as in Joel's study - it is like drawing a street map and deducing from it how much traffic there is in each case. Functionally, male and female brains are very different, not better or worse, but different. They are exposed to different hormones during embryonic development and in turn regulate hormone production in the male and female bodies in different ways.

Monthly rhythm in the brain

According to Julia Sacher from the Max Planck Institute for Human Cognitive and Brain Sciences, hormones actually have a major influence on the function and structure of the brain. The volume of gray and white matter in the hippocampus, a brain region with a central role in memory, mood and emotions, changes over the course of the cycle, as the researchers observed in a pilot study with a test person.

In female mice it has already been established that not only the hippocampus but also various behaviors are subject to a kind of monthly cycle. A larger study will show whether this also applies to humans. In it, the researchers will review their observation from the pilot study and examine the effects on human behavior. "If, for example, it turns out that women are particularly receptive in certain phases of their monthly cycle, this could possibly be used for psychotherapy," says the neuroscientist.

During pregnancy, too, there are adjustments in the structure of the brain, which can last for up to two years, as a recent study by Elseline Hoekzema from the Universitat Autònoma de Barcelona showed. She examined the brain structure and function in women before, during and after pregnancy and found a decrease in volume in several regions of the cerebral cortex and in the hippocampus. The examples showed that the brain is very plastic and adapts to different circumstances and requirements, says Sacher.

Innate or learned

In fact, the brain is very adaptable and is not only shaped by hormones, but also by experiences and activities. In London taxi drivers, for example, who have to memorize the entire road network in the course of their training, the volume in the hippocampus, which plays a role in memory and spatial orientation, increases. In pianists, the motor cortex that controls the hands and the auditory cortex change. In golfers, the areas of the brain that are involved in controlling golf.

"And because men and women in our society have different roles and professions for cultural reasons, this can also lead to gender-specific differences in brain structure and function," says Jäncke. It is therefore problematic if the results from such studies are used to explain supposedly gender-specific behaviors or skills. Instead of belittling the differences or exaggerating them, Sacher believes that you should simply raise them once. Without evaluating the results and, above all, without using them to cement certain role models.