Double training promotes retinotopic transfer of category learning

Perceptual learning is traditionally retinotopically constrained, whereas category learning is thought to generalize across the visual field. Recent evidence challenges this distinction by showing that information-integration (II) category learning can also exhibit visual-field specificity. We investigated whether II learning transfers across retinal locations using a double-training paradigm. Participants learned to categorize gratings at one peripheral location, and transfer was tested at the opposite hemifield. We replicated visual-field specificity and found that transfer depended on the temporal order of training. Double training, with simultaneous or subsequent passive exposure to an irrelevant task at the untrained location, enabled robust transfer, whereas performing the irrelevant task before category training abolished it. This order-dependent pattern mirrors double-training effects in perceptual learning, suggesting that II category learning and perceptual learning share principles of location-specific plasticity and flexible transfer. These findings shed light on mechanisms of visual learning and inform strategies to enhance transfer.