Conference on Cognitive Computational Neuroscience

The perception of sensory stimuli is frequently variable. Previous studies have shown that observers account for uncertainty arising from internal variability when they combine sensory cues, integrate sensory input with prior expectation, or select actions under externally imposed cost functions. But how does the distribution of internal uncertainty shape free perceptual report? Behavioural models have assumed that unitary percepts may reflect means, modes or samples of internal belief distributions. Here, we show that observers' reconstructions of the remembered orientation of a visual grating correspond to means of the variability-induced posterior, not the mode or a random sample. This behaviour remains robust as either the distribution of stimuli, or the degree of internal variability, change. These observations suggest that variability arises in encoding or recall, and is accurately taken into account at the point of perception or action.