Phasic changes in pupil size are strikingly low-dimensional! In a new preprint, we show that very different tasks and processes map onto a very similar, low-dimensional latent space. We suggest that phasic changes in pupil size originate from a set of distinctive fingerprints that describe a pupillary manifold: a latent space that is highly constrained by the underlying physiological structures, i.e. the balance between different branches of the ANS.
