The effect of background and presentation mode on transparent layer constancy

We investigated the degree of transparent layer constancy when matching filter colors across different illuminations. Previous studies reported varying degrees of constancy and it was suggested that constancy is not influenced by whether or not the subjects have a transparency impression. We systematically examined the role of viewing context and phenomenal impression on constancy performance. We compared normal filter presentation that leads to phenomenal transparency with a flipped filter version that violates geometric transparency cues and appears opaque (X- vs T-junctions). Two different background structures were used and we also varied the presentation mode (static vs motion, monocular vs stereo, simultaneous vs alternating display of test and standard). We found that the geometric cues had the largest effect on transparent layer constancy: It was significantly higher with X-junctions than with T-junctions. Alternating presentation of standard and test enhanced constancy throughout. The effects of motion, stereo and background structure were smaller and more complex: While in the case of X-junctions constancy was enhanced when the objects were moving or presented in a more structured background pattern it was reduced with T-junctions. Together, this suggests that the more vivid the impression of a transparent layer is the higher the degree of constancy.