The McCollough World: Induction of orientation-contingent aftereffects with an altered-reality system.

The McCollough Effect is a color aftereffect produced by exposure to colored, oriented patterns. For example, following adaptation to vertical red and horizontal green stripes in alternation, vertical black and white patterns appear greenish, while horizontal black and white patterns appear reddish. The striking aspect of the McCollough Effect is that just a few minutes of adaptation can produce an aftereffect lasting days or weeks. Though this effect is easily induced, previous work has shown that stronger effects can be achieved with longer periods of adaptation. To allow especially long adaptation durations, the current work develops a novel method of induction of the McCollough Effect using live video feed, filtered by orientation, and viewed with a head-mounted display. Results showed that this "McCollough World" paradigm was as strong an inducer (per unit time) as traditional paradigms using gratings, while allowing observers to adapt comfortably for multiple hours. Two hours of McCollough World adaptation produced effects that were significantly larger than 20 min of traditional adaptation, which is close to the tolerance limits for gratings. This work provides insight into the features necessary for induction of the McCollough Effect and provides a strategy for creating especially strong and long-lasting color aftereffects.