Loewenstein's & Ahissar's Labs: Paper of the Month, March 2021

Yonatan Loewenstein, Ofri Raviv, Merav Ahissar
Dissecting the Roles of Supervised and Unsupervised Learning in Perceptual Discrimination Judgments
Journal of Neuroscience 27 January 2021, 41 (4) 757-765;

Lay summary

The seemingly effortless process of inferring physical reality from the sensory input is highly influenced by previous knowledge, leading to perceptual biases. Two common ones are contraction bias (the tendency to perceive stimuli as similar to previous ones) and choice bias (the tendency to prefer a specific response). Combining human psychophysical experiments with computational modeling we show that these biases reflect two different learning processes. Contraction bias reflects unsupervised learning of stimuli statistics, whereas choice bias results from supervised or reinforcement learning. This dissociation reveals a hierarchical, two-stage process. The first, where stimuli statistics are learned and integrated with representations, is unsupervised. The second, where a binary judgment is applied to the combined percept, is learned in a supervised way.