The role of frames of reference in the development of responsiveness to shading information.

The use of frames of reference in interpreting shading information in pictures was studied with children from 3 to 8 years of age. After learning to discriminate tactually between a convexity and a concavity, the subjects were presented a photograph of the convexity and the concavity in which the only information for differential shape was provided by the relationship between the orientation of the shading on the shapes and the frames of reference. By changing the position of the subject's head, rotating the display, and changing the location of the source of illumination, the relevance of egocentric, environmental, and lighting-specified frames of reference was manipulated. Children in this age range were found to be sensitive to shading information for depth, both when that information was specified by only a single frame of reference and when all three frames of reference were relevant. Differences in the responsiveness to individual frames of reference were found: the egocentric (head-retina) frame of reference was most effective, followed by the environmental reference frame, and finally by the frame of reference based on the location of the light source in the space surrounding the photograph. Responsiveness to the environmental and lighting-based frames of reference increased with age, while responsiveness to the egocentric frame of reference was high for all age groups and did not increase with age.