Metacognition in putative magno- and parvocellular vision.

Abstract

A major distinction in early visual processing is the magnocellular (MC) and parvocellular (PC) pathways. Prior work has theorized that the PC pathway more strongly contributes to conscious object recognition via projections to the ventral ``what'' visual pathway, whereas the MC pathway underlies non-conscious, action-oriented motion and localization processing via the dorsal stream ``where/how'' pathway. This invites the question: are we equally aware of activity in both pathways? And if not, do task demands interact with which pathway is more accessible to awareness? We investigated this question in a set of two studies measuring participants' metacognition for stimuli biased toward MC or PC processing. The "Steady/Pulsed Paradigm" has two conditions that present brief stimuli alongside temporally distinct luminance pedestals, thought to bias stimulus processing to either pathway. Experiment 1 was a spatial localization task thought to rely on information relayed from the MC pathway. Using both a model-based and model-free approach to quantify participants' metacognitive sensitivity to their own task performance, we found greater metacognitive efficiency in the steady (MC-biased) condition compared to the pulsed (PC-biased) condition. Experiment 2 was a fine-grained orientation-discrimination task more reliant on PC pathway information. Our results show an abolishment of the MC pathway advantage seen in Experiment 1 and suggest that the advantage in metacognitive efficiency for MC processing may hold for stimulus localization tasks only. More generally, our results highlight the need to consider the possibility of differential access to low-level stimulus properties in studies of visual metacognition.