Big Study Finds Brain Gray Matter and Cortical Thickness Peak at Age 6 or Earlier, Contradicting Brain Dogmas

A new study published in Nature (with very many listed authors)  has produced a result very relevant to claims that the human mind is produced by the brain.  Entitled "Brain Charts for the Human Lifespan," the paper says, "We aggregated 123,984 MRI scans, across more than 100 primary studies, from 101,457 human participants between 115 days post-conception to 100 years of age."  MRI scans are a type of scan that allow you to see the physical structure of the brain. 

Human experience is that intelligence roughly peaks around age 20, with no major decline before age 40.  The lack of intellectual decline before age 40 is partially why nations generally elect leaders that are 40 years old or older, and it is partially why major corporations generally have as their Chief Executive Officer someone who is age 40 or older.    The claim has often been made that gray matter in the brain is some type of neural matter particularly associated with intelligence. It has often been claimed that you think with the gray matter of your brain.  Given human intelligence peaking around age 20, and not declining much before age 40, such claims predict that gray matter in the brain should peak at around age 20, without much decline before age 40. 

But this is not at all what the "Brain Charts for the Human Lifespan" study found. It found that gray matter in the brain peaks at around age 6, with about a 12% decline by age 20, and about a 20% decline by age 40.  This is shown in a chart from the paper:

From the "Brain Charts for the Human Lifespan" paper

According to this chart:

• Gray matter volume peaks around age 6;
• gray matter volume declines by about 12% by age 20;
• gray matter volume declines by about 20% by age 40;
• cortical thickness peaks by about age 2 or 3;
• cortical thickness declines by about 10% by age 20;
• cortical thickness declines by about 15% by age 40;
• white matter volume peaks at about age 30.

The chart above is a bit hard to read, but at a web site set up by the paper authors, the gray matter volume trend by age is graphed in the easy-to-read graph below:

 Source: https://brainchart.shinyapps.io/brainchart/

The data presented in the new study simply does not match human experience regarding intelligence and age.  I cannot cite any numbers showing a growth of IQ by age, because IQ tests are designed to test differences in either children of one age or adults.  But the following are simple facts of human experience

• Children age 6 have an intelligence that only seems to be 50% or smaller than the intelligence of adults (despite the gray matter volume peaking around age 6);
• adults of age 40 do not have an intelligence noticeably less than those of adults at age 20, and have an intelligence much greater than those age 6 or younger (despite such 40-year-olds having 20% less gray matter volume than those age 6, about 15% less cortical thickness than those age 2, and roughly 10%  less gray matter volume than those age  20);
• adults of age 20 have an intelligence much higher than children of age 6 (despite such 20-year-olds having about 12% less gray matter volume than those age 6, and about 10% less cortical thickness than those age 2 or 3);
• adults of age 30 do not seem any smarter than adults age 20 (despite such 30-year-olds having white matter volume peaking at their age);
• children with an age of about 2 or 3 have an intelligence that only seems to be a small fraction of the intelligence of adults (despite their cortical thickness peaking around this age). 

Once again, the "brains make minds" dogma gigantically flunks an empirical test. But you won't hear about this failure in the mainstream media, which tends to keep scientists and the public in a "filter bubble" that allows them to keep thinking that their cherished dogmas are holding up well, no matter how miserably such dogmas are failing empirical tests. So, for example, a Nature article on the "Brain Charts for the Human Lifespan" study completely fails to mention how dramatically the study's data conflicts with human experience about how intelligence changes with age.