It's common in neuroimaging papers to flaunt t, Z, or p values with color bars and tables, but rarely show the actual effect sizes. It’s like physicists discussing the speed of light but only reporting a p-value—great for maintaining a sense of mystery. The issue you're raising resonates with concerns we’ve been advocating for years, as highlighted in this paper and a recent blog post.
Although I'm not familiar with the specifics of RSA, the group-level average correlation values you mention, mostly in the range of [0, 0.02], are concerning. Such small values, coupled with likely low cross-individual variability, can easily result in superficially high statistical values. Without direct access to your data, it's hard for me to evaluate the situation fully. However, I recommend taking a closer look at the entire RSA process to ensure accuracy. Let me know if there's any further assistance I can provide.
Gang Chen