Viewpoint and Orientation Influence Picture Recognition in the Blind

Drawing as a tool for investigating the nature of imagery representations of blind people: The case of the canonical size phenomenon

Several studies have shown that blind people, including those with congenital blindness, can use raised-line drawings, both for "reading" tactile graphics and for drawing unassisted. However, research on drawings produced by blind people has mainly been qualitative. The current experimental study was designed to investigate the under-researched issue of the size of drawings created by people with blindness. Participants (N = 59) varied in their visual status. Adventitiously blind people had previous visual experience and might use visual representations (e.g., when visualising objects in imagery/working memory). Congenitally blind people did not have any visual experience. The participant's task was to draw from memory common objects that vary in size in the real world. The findings revealed that both groups of participants produced larger drawings of objects that have larger actual sizes. This means that the size of familiar objects is a property of blind people's mental representations, regardless of their visual status. Our research also sheds light on the nature of the phenomenon of canonical size. Since we have found the canonical size effect in a group of people who are blind from birth, the assumption of the visual nature of this phenomenon - caused by the ocular-centric biases present in studies on drawing performance - should be revised.

Typology of Tactile Architectural Drawings Accessible for Blind and Partially Sighted People

The subject of this research is architectural typhlography—tactile drawings, dedicated to the blind and thematically related to architectural objects and spaces of various scales. This collection is very diverse and includes both representations of specific spaces as well as adaptations of ordinary (visually accessible) architectural drawings. The phenomenon of typhlographics has not yet found an appropriate scientific emplacement in the architectural discipline. Based on the collected research material, including Polish and foreign studies, the authors have made a multi-criterial division of the tactile drawings according to specific criteria. The result of the research is a pioneering typology of architectural typhlographs, made in seven categories. This publication, organizing the issues of architectural typhlographs and proposing a unified terminology of the phenomena and concepts studied, may be used by other researchers who explore the subject of the accessibility of architectural space for the blind.

Haptic Object Recognition is View-Independent in Early Blind but not Sighted People

Object recognition, whether visual or haptic, is impaired in sighted people when objects are rotated between learning and test, relative to an unrotated condition, that is, recognition is view-dependent. Loss of vision early in life results in greater reliance on haptic perception for object identification compared with the sighted. Therefore, we hypothesized that early blind people may be more adept at recognizing objects despite spatial transformations. To test this hypothesis, we compared early blind and sighted control participants on a haptic object recognition task. Participants studied pairs of unfamiliar three-dimensional objects and performed a two-alternative forced-choice identification task, with the learned objects presented both unrotated and rotated 180° about they-axis. Rotation impaired the recognition accuracy of sighted, but not blind, participants. We propose that, consistent with our hypothesis, haptic view-independence in the early blind reflects their greater experience with haptic object perception.

Pointing to azimuths and elevations of targets: blind and blindfolded-sighted

Three groups of observers pointed to target circles in a path on the ground, in two parallel rows. Participants in one group viewed the circles and then pointed blindfolded. Those in a second group were blindfolded and then touched the circles with a stick while walking past them. Volunteers in the third group were blind adults, a diverse group, who also used a stick to detect the circles. For all three groups, as distance to the circles increased, pointing azimuths shrank and elevations increased. We suggest that directions to targets on major environmental surfaces may be appreciated similarly by the blind and sighted. We challenge the assumption that the principle of convergence to the horizon, available through vision because of the way in which visual angle decreases on the retina, is not available through touch.

Elevation easier than plan for sighted and early-blind adults in a perspective-taking task

Plans show shapes of objects from above, and represent both their left-right order and their order in the z-dimension (the distance of the objects). Elevations show only the vertical shapes of objects arranged from left to right. Plans, having more spatial information, may be more difficult for participants to construct. Results from a study with sighted, sighted-blindfolded, and early-blind participants on Piaget's perspective-taking three-mountain task support this hypothesis. The plan task was judged more difficult than the elevation task even when participants performed with the same level of accuracy on both tasks. In visual and tactile tasks, amount of spatial-order information may determine difficulty, rather than plan versus elevation per se.

Haptic Object Recognition: How Important are Depth Cues and Plane Orientation?

Raised-line drawings of familiar objects are very difficult to identify with active touch only. In contrast, haptically explored real 3-D objects are usually recognised efficiently, albeit slower and less accurately than with vision. Real 3-D objects have more depth information than outline drawings, but also extra information about identity (eg texture, hardness, temperature). Previous studies have not manipulated the availability of depth information in haptic object recognition whilst controlling for other information sources, so the importance of depth cues has not been assessed. In the present experiments, people named plastic small-scale models of familiar objects. Five versions of bilaterally symmetrical objects were produced. Versions varied only in the amount of depth information: minimal for cookie-cutter and filled-in outlines, partial for squashed and half objects, and full for 3-D models. Recognition was faster and much more accurate when more depth information was available, whether exploration was with both hands or just one finger. Novices found it almost impossible to recognise objects explored with two hand-held probes whereas experts succeeded using probes regardless of the amount of depth information. Surprisingly, plane misorientation did not impair recognition. Unlike with vision, depth information, but not object orientation, is extremely important for haptic object recognition.

The influence of facing direction on the haptic identification of two-dimensional raised pictures

It has been hypothesized (Lederman et al, 1990 Perception & Psychophysics 47 54-64) that sighted people adopt a visual translation process when attempting to identify 2-D raised images by touch they employ a visual image as a mediator between haptic sensory information and the object representation. If this hypothesis is correct, the performance in identifying pictures by touch (with eyes closed) ought to be better when the head is facing the picture than when facing in a very different direction. In this study, thirty-six blindfolded participants were required to identify raised pictures of common objects with their head facing either in the same direction as the raised picture or in an orthogonal direction. Identification performance was measured in terms of accuracy and response latencies. Overall, participants were more accurate and faster when their heads faced in the same direction as the picture. This finding is discussed in terms of spatial congruency between haptic representations of pictures and visual (or spatial) imagery created during exploration of haptic pictures.

Perceptual learning of view-independence in visuo-haptic object representations

We previously showed that cross-modal recognition of unfamiliar objects is view-independent, in contrast to view-dependence within-modally, in both vision and haptics. Does the view-independent, bisensory representation underlying cross-modal recognition arise from integration of unisensory, view-dependent representations or intermediate, unisensory but view-independent representations? Two psychophysical experiments sought to distinguish between these alternative models. In both experiments, participants began from baseline, within-modal, view-dependence for object recognition in both vision and haptics. The first experiment induced within-modal view-independence by perceptual learning, which was completely and symmetrically transferred cross-modally: visual view-independence acquired through visual learning also resulted in haptic view-independence and vice versa. In the second experiment, both visual and haptic view-dependence were transformed to view-independence by either haptic-visual or visual-haptic cross-modal learning. We conclude that cross-modal view-independence fits with a model in which unisensory view-dependent representations are directly integrated into a bisensory, view-independent representation, rather than via intermediate, unisensory, view-independent representations.

The Influence of Viewpoint and Object Detail in Blind People When Matching Pictures to Complex Objects

We examined haptic viewpoint effects in blindfolded-sighted (BS) and visually impaired subjects: early blind (EB), late blind (LB), and very low vision (VLV). Participants felt complex objects and matched tangible pictures to them. In experiment 1, the EB and BS subjects had similar overall performance. Experiment 2 showed that the presence of a detail on the target object lowered performance in the BS subjects, and that matching accuracy was lower overall for top views for the blind subjects. In experiments 3–5, EB, LB, VLV, and BS subjects made judgments about perspective pictures of a model house with more salient object details. In experiment 3, performance was higher for side views than for corner views. Elevated side views were identified more readily than elevated corner views in experiment 4. Performance for top views was higher than for elevated side views in experiment 5, given the relative simplicity of the top-view depictions and salient details. The EB and BS participants had somewhat lower matching accuracy scores than the other groups. We suggest that visual experience is helpful, but not essential for picture perception. Viewpoint effects may vary with experience and object complexity, but the relevant experience need not be specifically visual in nature.