Interocular transfer of orientation-contingent color aftereffects with external and internal adaptation

The issue of whether McCollough effects transfer interocularly was examined in two experiments. In Experiment 1, as in previous experiments, no interocular transfer of McCollough effects was obtained when subjects adapted monocularly to externally present patterns with their unused eyes fully occluded. However, when subjects adapted monocularly (with the unused eye fully occluded) to visual images of those patterns superimposed on physically present chromatic backgrounds, McCollough effects transferred interocularly. In Experiment 2, subjects adapted to either physically present patterns or to images of those patterns (as in Experiment 1), but the unused eye was exposed to unpatterned diffuse white light. In contrast to Experiment 1, the externally adapted subjects showed interocular transfer of McCollough effects. In Experiment 2, the magnitude of the interocular transfer effects produced by imagery was significantly larger than the magnitude of the effects produced by external adaptation, but the magnitude of the imagery-induced aftereffects did not differ from Experiment 1 to Experiment 2. These results extend earlier findings by Kunen and May (1980) and show that McCollough effects can be produced through adaptation to imagery, even though the direction of the imagery-induced aftereffects indicates adaptation to higher spatial frequencies whereas externally derived aftereffects indicate adaptation to lower spatial frequencies. It is concluded that failure of previous studies to obtain interocular transfer of McCollough effects may have resulted from complete occlusion of the contralateral eye. These data point up some interesting similarities and some important differences between imagery and actual vision. The implications for analogical models of visual imagery are discussed.