http://www.pnas.org/content/early/2013/11/27/1316909110
The data in the study concerned are derived from a technique called
diffusion tensor imaging (DTI), which estimates how water diffuses along
white matter tracts in the brain. The big advantage of DTI is that it
can be used in living humans. Its big disadvantage is that even at best
it gives only a very low resolution and thus partial picture of possible
connections in the brain, and DTI is also rather poorly validated
against 'gold standard' anatomical tracing methods that are routinely
used in animal experiments. Thus, of the billions of connections made
via the white matter of the human brain, DTI detects a tiny fraction of
a percent and the method only indicates hypothetical anatomical
connections and not any function. As a reality check one should take the
example of the nematode worm, C elegans, which is the only animal for
which we have a complete map of every connection in its nervous system.
It has 302 neurons, compared to 85 billion in the human brain, yet no
neuroscientist (or journalist) can tell you what is in the mind of this
worm. Our knowledge of the connections in the human brain is
poverty-stricken by comparison, yet this has not stopped some
neuroscientists from linking their hypothetical structures of human
neural networks, derived from techniques like DTI, directly to complex
psychological process, as in the paper under discussion. Worse still,
the media reinterpret and amplify the scientists conjectures to build
their own confection of irresponsible speculation that bears little
relation to the original data, as the present case so ably illustrates.
- K. Martin
3 comments:
Scientifically, this study is also weak on several other levels:
1) The reported differences between the two groups (men and women) appear to be often inexistant or in many cases or marginal.
2) Even if the tracing results and behavioral results were true, this would be only just a correlation. The whole study's interpretation suggest a causal link "women are hardwired to...", this is nonsense.
3) Many statements are extremely poorly defined...who really knows what is meant by linking analytical and intuitive processing modes? The underlying message promotes the stereotype that women are somewhat less analytical than men.
4) The authors apparently didn't correct for brain size differences : men are on average bigger, have thus slightly larger brains. Connectivity differences might just reflect this size difference and have nothing to do with function per se.
5) The study never considers that any observed change in brain structure might be the resuls of social roles and expectations imposed on men and women by society.
In my eye, such a study just vehiculates unsubstantiated sexist stereotypes.
A final comment to the remark that such stereotypes exist for a reason...yes, they do, the main reasons I see is ignorance.
Agree. And the the study from which these data come from includes behavioral measures; the fact that the authors do not show any relationship of the wiring data with the behavioral stuff makes me think they didn't find any?
more comments along the same line in the guardian
http://www.theguardian.com/science/2013/dec/07/brain-science-ditch-male-female-cliche
or here
http://theconversation.com/new-insights-into-gendered-brain-wiring-or-a-perfect-case-study-in-neurosexism-21083
Our data of the connections within the human brain is poor by comparison; nevertheless this has not stopped some neuroscientists from linking their hypothetic structures of human neural networks, derived from techniques like DTI, on to complicated psychological method, as within the paper underneath discussion. The information within the study involved are derived from a method known as diffusion tensor imaging that estimates however water diffuses on nervous tissue tracts within the brain.
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