Are male and female brains connected in a completely different manner?

Question

I found this claim on Focus, an Italian pop-sci magazine:

Le reti di connessioni cerebrali nel cervello dei maschi (in alto) e in quelle donne (in basso): in blu sono visibili i collegamenti all'interno dello stesso emisfero, in arancione quelli tra un emisfero e l'altro.

(my translation)

The networks of cerebral connections in the brain of males (top) and in those [sic] females (bottom): same-hemisphere connections are visible in blue, connections across hemispheres are in orange.

It seems extraordinary to me that males have basically only same-hemisphere connections and females only across? Is this image "lying", not showing both types of connections for both genders? The article claims scientific accuracy and to report a scientific paper: does this image represent its conclusions in a fair manner?

It's fairly important to correct any mistakes because this is being repeated by many anti-gay groups (e.g. this or this)

Answer 1

Is this image "lying", not showing both types of connections for both genders? The article claims scientific accuracy and to report a scientific paper: does this image represent its conclusions in a fair manner?

Well, it's certainly reporting some of the conclusions correctly. But it's not telling the whole truth.

The article doesn't seem to give the exact name of the study mentioned, but it does name Ragini Verma as leading the study. This supports my original hypothesis that Sex differences in the structural connectome of the human brain is the study cited - Verma is one of the authors.

Quoting from the paper's abstract:

In all supratentorial regions, males had greater within-hemispheric connectivity, as well as enhanced modularity and transitivity, whereas between-hemispheric connectivity and cross-module participation predominated in females. However, this effect was reversed in the cerebellar connections.

This is re-stated later in the paper:

Most supratentorial connections that were stronger in males than females were intrahemispheric (permutation-tested P < 0.05). In contrast, most supratentorial connections that were stronger in females were interhemispheric. However, in the cerebellum, the opposite pattern prevailed, with males showing stronger connections between the left cerebellar hemisphere and the contralateral cortex.

So the claim is really only supported in one region of the brain, not all regions.

Note the phrasing here. It doesn't say that there are more connections between hemispheres in one gender and more connections inside hemispheres in the other gender, but rather that strength is different. Not necessarily number.

The article only tells half of the truth. Consider it untruthful.

The image, by the way, is from Figure 2 of the paper. The caption reads:

Fig. 2. Connection-wise analysis. (A) Brain networks show increased connectivity in males (Upper) and females (Lower). Analysis on the child (B), adolescent (C), and young adult (D) groups is shown. Intrahemispheric connections are shown in blue, and interhemispheric connections are shown in orange. The depicted edges are those that survived permutation testing at P = 0.05. Node color representations are as follows: light blue, frontal; cyan, temporal; green, parietal; red, occipital; white, subcortical. GM, gray matter.

Sections B, C, and D are not shown in the article's use of the image.

Answer 2

The study being referenced is almost certainly Sex differences in the structural connectome of the human brain by Ingalhalikar et al, PNAS 111 (2) 823-828.

The description of the figure in the Italian article is entirely wrong. It is not meant to show "the network of connections in the brains of males and females", but connections whose strength was significantly larger on average over the male subjects and over the female subjects.

Strangely, at no point in the paper are any specific numbers attached to these differences. The paper says, as I did above, that they are "significant", but that only means that they are statistically significant—i.e., that the study had a large enough sample size to prove that there is a difference—not that the difference is large. Also, those differences are between group averages, not between individuals in each group. It's possible for group A to have significantly higher average frobbiness than group B, while the chance that a random member of group A has higher frobbiness than a random member of group B is close to a coin flip, if the variance is larger than the difference between the means. That may or may not be the case here; it's impossible to know since no relevant numbers are provided.

The objections in the previous paragraph were raised in a letter published in the same journal: "On the mis-presentation and misinterpretation of gender-related data: The case of Ingalhalikar’s human connectome study", PNAS 111 (6) E637. The original authors replied, but the reply fails to show an understanding of the objections, as far as I can tell.

I'll also note that the authors themselves seem highly confident that the connectivity differences are related to specific sex differences, saying in the abstract

Males have better motor and spatial abilities, whereas females have superior memory and social cognition skills. [...] [our] results suggest that male brains are structured to facilitate connectivity between perception and coordinated action, whereas female brains are designed to facilitate communication between analytical and intuitive processing modes.

although none of that is actually supported by their results. They don't seem to have considered that the differences they found might be predicted by brain volume or some other low-level property. My impression is that confirmation bias affected the design and analysis of the study.