alt Hacker News"This approach was also able to identify subgroups of children with different levels of cognitive control and performance monitoring, or the ability to modify one’s strategy after making an error."
This should surprise no one. You took a large population and found subpopulations within it. If you want to look at a population average, then use the population data. If you want to look at kids with specific attention needs (guessing ADHD since medical related) then design a study to select for children fitting that criteria, including subtypes.
This seems like the type of thing that should have had a study about study design done long ago that they could have followed to help them structure their own population selection.
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The point isn’t that they found subgroups, the point is the method they used to find them — namely, analyzing individual brain scans rather than averaging them out first.
Often reminded of this passage from Hitchhiker's:
The Maximegalon Institute of Slowly and Painfully Working Out the Surprisingly Obvious (MISPWOSO) is a fictional research institution from Douglas Adams' The Hitchhiker's Guide to the Galaxy series.