Tactile displays for navigation and orientation : perception and behaviour

Abstract

Perceiving and understanding information of, for example, a visual navigation display may be difficult for people with a visual challenge or in situations where the user's visual sense and cognitive resources are heavily loaded. Developing information presentation schemes that reduce the threat of overloading eyes and mind becomes increasingly important. Employing the sense of touch can reduce the reliance on the visual system. By developing an intuitive information presentation concept, we may also lessen the cognitive load. In the tactile sense, an intuitive presentation concept may be based on the proverbial tap-on-the-shoulder. For instance, a localized vibration on the torso can present the direction of a waypoint. The first two questions addressed in this thesis are concerned with the spatial resolution of the torso for tactile stimuli, and the role of the timing parameters of the presentation. We found a uniform acuity of 3 - 4 cm for most of the torso. The burst duration of the presentation has only a small effect on the acuity, but the Stimulus Onset Asynchrony (SOA) is an important determinant of performance: A smaller SOA requires a larger distance between stimuli. The third question concerned the ability to determine the absolute location of stimuli. Observers could localize stimuli within 5 cm from their veridical location. Mislocalizations were mainly along a line originating from the body midaxis. The fourth and fifth question addressed how accurate users couple a direction to a localized vibration, and how observers determine a direction based on a single point stimulus. There is a bias in perceived directions toward the midsagittal plane, but observers are consistent in their direction determination. Observers used two internal reference points (one for each torso half) to determine the direction of the point stimulus. The sixth question concerned the crossmodal visual-tactile perception of space and time. The experimental results indicate that the same internal representation is used in unimodal and multimodal comparisons. The last three questions addressed the behavioural aspects of tactile displays for navigation and orientation. Question 7 looked at the effect on mental effort ratings when a tactile display is present together with, or instead of, visual information. The results show that users rate the required mental effort as lower when they have a tactile display at their disposal. The next relevant question then becomes whether a tactile display can make users immune for (high levels of) mental workload. We found mixed results. We hypothesised that this issue may depend on the design of the tactile information. Favourable effects on performance were found across all tasks tested, including vehicle waypoint navigation, target interception in a jet fighter, maintaining a stable hover in a helicopter, and orienting in microgravity. We conclude that in comparison to a baseline with visual information, tactile displays can improve performance and lower the risk of sensory and cognitive overload in navigation and orientation tasks.