Distal target localization by the blind

Citation: 
Bruggeman, H., Giudice, N.A., Stankiewicz, B.J., & Legge, G.E. (2000). Distal target localization by the blind. Annual Meeting of the Association for Research in Vision and Ophthalmology, Supp. IOVS, 40, S431, Ft. Lauderdale, FL.
Abstract: 
Purpose. An important component of spatial navigation is the ability to localize and approach distal targets. For example, to enter a building one has to find important structural features such as the entrance, the elevator and room signs. These landmarks are difficult to localize and identify for people who are blind or have low vision. We investigated the use of a hand-held device with auditory feedback that could assist them in the localization of these salient landmarks/targets. The device consisted of a flashlight that provided auditory feedback when the beam contacted a target. We studied the effect of beam width and target size on the performance to initially localize and physically touch a target in a room. Method. Starting in the middle of a small room, 9 blind-folded participants were instructed to first localize and subsequently approach and touch a target at an unknown location that was 9.3 feet from the subject. Subjects scanned the room with a flashlight and received auditory feedback each time the target was illuminated. The design incorperated 4 beam widths (.25, 9, 35, and 73 degrees), and 3 target sizes (1x1; 5x5 and 25x25 inch). We measured the time to localize the target and the time to touch the target once it had been localized. Results. For the localization task there was a main effect of beam width (p<0.05) but no effect of target size. For the touch task, there was a main effect of both beam width (p<0.05) and target size (p<0.05) (note, with the smallest beam width, subjects were not able to touch the target in the allotted time). The 35-degree beam width produced the fastest touch time and in the localization the 35- and 73-degree beam widths showed no difference. Conclusions. When localizing a target, beam width plays an important role while target size has no effect on performance. However, if the observer needs to touch the target, then both target size and beam width play a critical role. Interestingly, bigger was not necessarily better. In both the localization and touch tasks the medium beam width facilitated the best performance.

Comments

This study provided data

This study provided data regarding the optimal cone size for detecting and localizing different sized targets during a search using an auditory feedback device. Results are instructive for understanding search strategy and interface design.