Sensory Perception & Interaction Research Group

Multi-function interfaces have become increasingly pervasive and are frequently used in contexts which pose multiple demands on a single sensory modality. Assuming some degree of modularity in attentional processing and that using a different sensory channel for communication can reduce interference with critical visual tasks, one possibility is to divert some information through the touch sense. The goal of this Thesis is to advance our knowledge of relevant human capabilities and embed this knowledge into haptic communication design tools and procedures, in the interest of creating haptically supported interfaces that decrease rather than add to their users’ sensory and cognitive load. In short, we wanted to create tools and methods that would allow the creation of haptic signals (accomplished via display of either forces or vibrations) extending beyond the one bit of communication offered by current pagers and cellular phone buzzers. In our quest to create information-rich haptic signals we need to learn how to create signals that are differentiable. We also need to study ways to assign meanings to these signals and make sure that they can be perceived clearly when presented one after another even in environments where their recipient might be involved with other tasks. These needs frame the specific research goals of this thesis. Most of the results described here were obtained through the study of tactile (in the skin) rather than proprioceptive (force feedback) stimuli. We begin by presenting several methods to create, validate and contrast tactile stimulus dissimilarity data and investigate the design of a waveform intended to be a tactile perceptual intermediate between a square waveform and a triangle waveform. Next, we explore methods to create and test tactile signal-meaning associations and document a surprising ability of participants to exhibit high recall of quickly learned associations at two weeks in a first examination of longitudinal recall of tactile stimuli. We then present methods to measure tactile stimulus masking and identify crucial perceptual thresholds relating to stimulus temporal spacing in an exploration into the masking effects of common-onset vibrotactile stimuli. Finally, we present methods to test haptic and multimodal perception in simulated scenarios including a method to simulate and control cognitive workload; and provide evidence that the commonly-used device of multimodal signal reinforcement can adversely impact performance in an ongoing primary task. The research presented in this Thesis has implications for the design of signals to be used in displays that are emerging in embedded computing environments such as cars, games, cellular phones, and medical devices.