Two-dimensional attributes in tactile depictions that convey three-dimensionality of objects.

Three-dimensional objects are readily identifiable in standardized representations like perspective/orthographic projections in the visual domain. While readily understandable visually, these representations are not easily interpretable by blind individuals, especially those congenitally blind. This leaves a major gap in their education and points to a need for investigating a representation technique to convey the volumetric attributes of an object. In this study, 5 geometric objects and 20 tactile representations were provided to 20 participants comprising born-blind, late-blind, and blindfolded-sighted individuals (aged 18-44). Each object was presented on tactile sheets in four different representation styles in randomized order: Generator-director, surface development, isometric view, and dual-view. Participants were first familiarized with the original objects via haptic exploration. Subsequently, they were presented with the aforementioned tactile representations, and for each stimulus, were required to indicate whether it related to any of the original objects. If identified, detailed descriptions were recorded for what features of a particular representation style made it relatable to the identified 3D object. Analysis of the data revealed that surface development and generator-director representation styles were better associated with the objects. Participants’ open-ended responses offer deeper insights into why certain representations were preferred over others. Factors included a better indication of surface details and more discernible spatial arrangements. Interestingly, some objects were well identified irrespective of the representation style they were depicted in, pointing to certain unique features present in all of the styles. We discuss tentative constituents of what makes a 2D representation align closely with its 3D counterpart, including local salient features and specific spatial configurations. These results offer hints regarding the cues that allow for translation between 3D structures and 2D tactile depictions, pointing to interesting questions regarding features that are informative in the visual versus tactile domains, and have relevance for conveying graphical information to blind students.