Just because the decision in a laboratory task was seemingly based on an image on the screen, doesn't make it a purely perceptual decision. Also applies for visually-guided movements vs spontaneous movements. Pointless debates in papers and on the internet.

It helps if I read this as '_we_ weren't super excited about this at this moment' than a value judgement. Sucks either way.

These data are from a recognition memory task which we have famously high capacity for. To begin to address how these high/low D representations are used to guide behavior, we can ask, is the spectral dimensionality different when the subjects report correctly or incorrectly? 3/3

In papers that report low D, the low variance dims are so because the high variance dimensions explain behavior. This really nice paper affirms previous results -- if behavior is not incredibly constrained by low d aspects of the stimuli/actions, activity is free to vary in many dimensions. 2/3

I'm a fan of this paper but I don't think previous studies report low dimensionality because the dataset wasn't large enough and, if I'm understanding the second reason correctly, the low-variance dimensions have never been meaningless. The utility of the dimensions for behavior matters hugely. 1/3

Hmm. I’d go further. If the participants were simply rating the same images on a scale of average redness to greenness, you’d see drastically lower dimensionality across cortex. This is an empirical question, of course.

Wait so if the participants in this paper were using the images to do something useful, you would see lower dimensionality?

www.cnbc.com/2025/12/03/l...