Transfer of illusion decrement: The effects of global versus local figural variations

The magnitude of many visual-geometric illusions decreases with continued inspection. This illusion decrement transfers from one illusion variant to another, with the magnitude of the transfer dependent on the apparent similarity between illusion figures. We conducted three experiments with the Müller-Lyer figure to assess factors controlling the transfer of decrement. Neither awareness of stimulus differences nor changes in local elements among the transfer and decrement figures differentially affected the magnitude of the transfer effect. However, global changes that altered the relationship between elements of the stimulus resulted in variations in the degree to which decrement training transferred among the illusion variants. This result has implications for our understanding of illusion decrement as a form of perceptual learning and also for our understanding of the relative processing priority of classes of figural features found in multilevel visual forms.