Conversions of Relief: on the perception of depth in drawings

Of the many ways in which depth can be intimated in drawings, perspective has undoubtedly been one of the most frequently examined. But there is also an equally rich history associated with other forms of pictorial representation. Alternatives to perspective became particularly significant in the early twentieth century as artists and architects, intent on throwing off the conventions of their predecessors, looked to new ways of depicting depth. In architecture, this tendency was exemplified by Modernism’s preference for parallel projection – most notably axonometric and oblique. The use of these techniques gave architects the opportunity to convey a new and uniquely modern form of spatial expression. At once shallow and yet expansive, a key feature of these drawings was their ability to support perceptual ambiguity. This paper will consider the philosophy and science of vision, out of which these preoccupations emerged. In this context, the nineteenth-century discovery of stereopsis and the invention of the stereoscope will be used to illustrate the way in which attempts to test the limits of spatial perception led to an opening up of visual experience; and provided a definition of visual experience that could encompass the representational ambiguities later exploited by the early twentieth-century avant-garde.

Allocentric spatial performance higher in early-blind and sighted adults than in retinopathy-of-prematurity adults

The question as to whether people totally blind since infancy process allocentric or ‘external’ spatial information like the sighted has caused considerable debate within the literature. Due to the extreme rarity of the population, researchers have often included individuals with Retinopathy of Prematurity (RoP – over oxygenation at birth) within the sample. However, RoP is inextricably confounded with prematurity per se. Prematurity, without visual disability, has been associated with spatial processing difficulties. In this experiment, blindfolded sighted and two groups of functionally totally blind participants heard text descriptions from a survey (allocentric) or route (egocentric) perspective. One blind group lost their sight due to retinopathy of prematurity (RoP – over oxygenation at birth) and a second group before 24 months of age. The accuracy of participants’ mental representations derived from the text descriptions were assessed via questions and maps. The RoP participants had lower scores than the sighted and early blind, who performed similarly. In other words, it was not visual impairment alone that resulted in impaired allocentric spatial performance in this task, but visual impairment together with RoP. This finding may help explain the contradictions within the existing literature on the role of vision in allocentric spatial processing.