CONTROVERSIAL DIFFERENCES
Greater social inequality between genders also revealed in brain scans
Major social differences can also be seen in the brains of women, a new study claims. Similar findings were observed in poor children in the U.S.
Klaus Taschwer
13 May 2023, 07:00
13 May 2023, 07:00
An MRI scan of a "normal" brain. Comparisons of nearly 8,000 such images showed correlations between social inequality and certain brain differences.
It's been another few years since books about the differences between male and female brains boomed. Almost two decades ago, the U.S. neuroscientist Louann Brizendine triggered a real boom with books such as "The Female Brain: Why Women Are Different from Men," in which innate differences between the sexes were no longer sought in hormones or genes alone, but in the brain.
However, such approaches overlooked, first, the fact that brains exhibit enormous plasticity and, second, that their development is highly dependent on environmental factors. In countries where social inequality between the sexes is greater, for example, women have a higher risk of developing neurological diseases, such as dementia. The latter was shown, for example, in China, where women are also more affected by the risk factors of lack of exercise and illiteracy.
Nearly 8,000 magnetic resonance images
As an international team of researchers led by Nicolas Crossley (Pontificia Universidad Católica de Chile) now claims, the consequences of strong social differences between the sexes can also be traced to stronger differences in the brains. This conclusion would allow the comparative analysis of nearly 8,000 magnetic resonance images of human brains from 29 countries, write Crossley and his team in the journal "PNAS".
According to these analyses, in countries with extensive gender equality (measured, among other things, by the Gender Inequality Index), virtually no differences were observed between the brains of men and women. In countries with greater inequality, however, the thickness of the right side of the cerebral cortex was lower in women.
Difficult to prove correlations
But is this finding really suitable as evidence that social inequality even shows up in the brains? The authors themselves admit to certain uncertainties of interpretation, but at least they provide possible hypotheses to explain their observations. For example, those regions of the cortex where the differences were found are associated with resilience to adversity. It was also observed that these regions become thinner during (post-traumatic) stress or depression.
Although the researchers do not establish a causal link, they hope their findings will provide arguments for policy measures to reduce inequality.
Colleagues interviewed about this who were not involved in the study expressed rather cautious opinions. For example, neuroscientist María Ruz (University of Granada) told the Spanish daily El País that the correlation between lower cortex thickness and experiences of physical violence is very difficult to prove. And doubts are also raised as to whether documented differences in brains actually provide a stronger "political" argument.
Support from US study
However, the new study is indirectly supported by a recent study from the USA. Researchers led by David Weissman (Harvard University) analyzed data from the Adolescent Brain Cognitive Development Study (ABCD study), specifically from more than 10,000 adolescents from 17 states that differ in their cost of living and anti-poverty policies.
Initial analyses of the ABCD data had found that children from lower-income families, compared with children from higher-income families, have a smaller volume of the hippocampus, which plays a critical role in memory and emotional learning.
Further analysis, the results of which appeared in the journal Nature Communications in early May, now showed that among children between the ages of nine and 11, differences in brain development and mental health were significantly smaller in those states that provide a stronger social safety net and have lower socioeconomic disparities. (tasch, 5/13/2023)
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