[fenazego]

This is not a case of Simpson's Parodox, at least the analogy about accuracy vs speed from the article isn't. You're not comparing global vs subgroup correlations. On the one hand you're measuring how speed and accuracy are correlated across the population when you ask subjects to solve a problem. On the other hand, (rather than measuring subgroup correlations) you're measuring how accuracy is affected when you ask an individual to speed up or slow down.

[amarshall]

The actual paper (linked in another comment here) is literally titled “Nonergodicity and Simpson’s paradox in neurocognitive dynamics of cognitive control”. Why they omit it from the blog post version, I’ve no idea.