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

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.

Adults' spatial scaling of tactile maps: Insights from studying sighted, early and late blind individuals

The current study investigated spatial scaling of tactile maps among blind adults and blindfolded sighted controls. We were specifically interested in identifying spatial scaling strategies as well as effects of different scaling directions (up versus down) on participants' performance. To this aim, we asked late blind participants (with visual memory, Experiment 1) and early blind participants (without visual memory, Experiment 2) as well as sighted blindfolded controls to encode a map including a target and to place a response disc at the same spot on an empty, constant-sized referent space. Maps had five different sizes resulting in five scaling factors (1:3, 1:2, 1:1, 2:1, 3:1), allowing to investigate different scaling directions (up and down) in a single, comprehensive design. Accuracy and speed of learning about the target location as well as responding served as dependent variables. We hypothesized that participants who can use visual mental representations (i.e., late blind and blindfolded sighted participants) may adopt mental transformation scaling strategies. However, our results did not support this hypothesis. At the same time, we predicted the usage of relative distance scaling strategies in early blind participants, which was supported by our findings. Moreover, our results suggested that tactile maps can be scaled as accurately and even faster by blind participants than by sighted participants. Furthermore, irrespective of the visual status, participants of each visual status group gravitated their responses towards the center of the space. Overall, it seems that a lack of visual imagery does not impair early blind adults' spatial scaling ability but causes them to use a different strategy than sighted and late blind individuals.

Piaget's 3-mountains task with impossible options: sighted, blindfolded, early and late blind participants

In Piaget's 3-mountains task, 3D objects - a cube, cone and sphere - sit on a square tabletop. They are portrayed in 2D pictures as elevations (projections to the sides) such as one with a square on the left, a triangle in the middle and a circle on the right. Three objects offer six elevations, of which four are possible and two impossible. The possibles are elevations from the sides of the table - front, left, right and rear. In the impossibles, an object in the corner of the table is shown in the middle of an elevation. Sighted, sighted-blindfolded, early- and late-blind adults judged the elevations as to side of the table or impossible. The results suggest similar spatial abilities across groups. The impossible options had mid-range accuracy for all groups, with reaction times like possible options. The sighted and blind participants may consider possible and impossible options sequentially, one item at a time.

Gibson and Pictures in Perspective: Reverse the Directions

In his extensive writing about pictures, James J. Gibson offered perspective formulae for square tiles projecting trapezoids onto a picture plane, foreshortening to zero height with distance. I reverse the claim: as distance decreases, the trapezoids increase to infinite height, in marginal distortion, or forelengthening. I also reverse the direction of projection. Usually considered to be incoming, from the distant tile to the picture plane, in reverse—outgoing—the tiles have directions from the center of projection, with implications for haptics and people who are blind. A drawing of a cube illustrates the argument. It is by an adult who is blind. It includes foreshortening, and shows directions of surfaces from a vantage point.

Inverse Sideways Perspective on a Road: A Drawing by a Blind Adult

An unusual drawing of a road has two lines converging sideways, from right to left. The left side of the picture is explicitly described as the location of the observer. Also, the fronts of the cars on the road face left, with the largest car on the right. This sideways perspective is novel. In linear perspective, roads running parallel with the picture surface should be drawn with parallel lines. Lines for roads running orthogonal to the picture surface should converge with elevation. The rule for roads is if converging, then upward, and if sideways, then not converging. The sketch is by a blind woman with modest experience in drawing, including perspective. It suggests an intermediate stage of drawing development, with inconsistent use of the observer's vantage point, in keeping with theories of perspective drawing by the blind and sighted of Willats, Kennedy and others.

The Role of Visual Experience in Changing the Size of Objects in Imagery Processing

Introduction

This paper investigates the question of whether or not subjects who are congenitally blind experience greater difficulties mentally in resizing images of objects than those who have low vision or are adventitiously blind.

Methods

Two experiments were conducted: one in which subjects were asked to mentally enlarge objects they previously explored manually, and one in which subjects were tested for the ability to demonstrate the change in the size of an object imagined to be moving away. Three groups of high school students with visual impairments took part in the experiment: congenitally blind, “late blind,” and those with low vision.

Results

When showing the linear size of an object enlarged in their imagination, congenitally blind participants overestimated its size more frequently than those who were late blind. The degree of mental reduction of the size of an object imagined to be moving away was comparable for all groups.

Discussion

The results suggest that the difficulties experienced by congenitally blind participants with the mental resizing of objects may be related to problems with performing mental scaling transformations. In the low vision group, the etiology of the subjects’ visual impairment was not taken into consideration. The group turned out to be heterogeneous with respect to imagery processes.

Implications for practitioners

When using models for explaining new concepts, it is important to ensure that congenitally blind learners understand the change of scale.