Measuring metacognition in hemianopic and blindsight patients: perceptual profiles and theoretical implications

Hemianopic patients with visual field defects due to cerebral damage sometimes demonstrate residual visual capacities in their contralesional field, known as blindsight. Its associated subjective experience remains poorly understood. We developed a novel task for patients combining forced-choice detection and discrimination paradigms with a confidence scale to assess individual objective sensitivity and metacognitive sensitivity and efficiency, addressing the unique challenges of probing subjective experience in hemianopia, where visual nature is rarely evident. Four patients participated, revealing distinct perceptual and metacognitive profiles. One patient exhibited remarkable contralesional objective capacities and some preserved metacognition despite rarely reporting visual perception, suggesting subjective content may not reflect the stimulus itself. Concomitantly, preliminary results reveal ipsilesional metacognitive impairments in three patients despite optimal objective performance. Overall, we present the first application of state-of-the-art metacognitive measures to hemianopia, bridging perceptual and metacognitive measures to explore subjective experience, offering new insights into blindsight and the dissociation between consciousness and metacognitive processes.