separate studies find no link between education & age-related brain shrinkage in humans, & different relationships between brain size & body size during the evolution of mammals  

original articles: Nyberg et al., 2021 (Proceedings of the National Academy of Sciences of the United States of America), Smaers et al., 2021 (Science Advances), reported in: The Daily Mail by Ian Randall on 26th April 2021 & The Conversation on 28th April 2021

this story was in episode 9 #education #atrophy #shrinkage #mammals

the error bar says

last episode we reported that human male & female brains are different in overall size, but not in their shape, structure or function. this episode, the Daily Mail tells us that a university eduction does not protect you from dementia, heart disease or brain shrinkage

in the study, thousands of brain scans from two national databases, covering 50 years of development showed that the most- & the least-educated halves of the volunteers showed the same rates of brain decay over their lifespan

level of education did predict overall brain volume & that was most strong for the important part of the brain that controls movements of the right hand

separately, Weisbecker & Smaers report in The Conversation on their study of the relative body & brain sizes of 1400 mammal species both fossilised & alive

scientists have previously considered the ratio of brain-to-body size as a measure of an animal's intelligence. but Smaers & colleagues point out that the same brain-to-body ratio has arisen in different ways during evolution. so we should not focus only on the evolutionary pressures for larger brains, but also to consider the pressures for smaller or larger bodies

is brain size & decay really unrelated to intelligence?

yes, it seems so

the large brain scanning study followed-up on hundreds of volunteers, with scans from the same people up to 11 years apart. this so-called longitudinal design is a better way to study changes in brain volume over time than other studies which only looked at a single time in each person's life

if i must quibble, the study only presents the data as a median split - divided into the most- & least-educated halves, the units on some graphs are wrong & god only knows why the brain area that controls the right hand is so important - but the analyses & conclusions seem fair. even the Daily Mail corrected a later version of their headline, limiting their conclusions to brain shrinkage - because dementia is well-known to be less common & brain size larger in people with more education

on the brain evolution study, i'm not expert enough to judge, but this paper has some beautiful data visualisations! the conclusion that intelligence is not a simple matter of brain size or brain-to-body ratio seems a perfectly sensible one


well, to decay at least


The Daily Mail: fair - scientific story mostly intact

The Conversation: fact - scientific story reported well