Development of Variable Attention Capture (Vac) Haptic Feedback Systems for Conveying Information at an Appropriate Level of Salience

As the proliferation of visual and auditory communication media push human information processing to its limits, many researchers turn to the haptic modality - the sense of touch - as a means of conveying information. Presently, most haptic feedback systems are focal feedback mechanisms designed to deliver alerting cues. However, not all tasks are urgent and require a person's immediate and focal attention, so these attention-capture methods may distract a user from more critical tasks. Recently, researchers have begun to investigate ambient feedback systems that convey peripheral information without distracting a user from a more important task. So far no efforts have been made to combine these two separate categories to create a unified system for haptic attention capture. We thus propose the development of variable attention capture (VAC) feedback methods as a new design paradigm for fluidly modulating a user's attention capture along a spectrum depending on task priority. This proposed VAC feedback paradigm will allow for the development of versatile next-generation haptic devices capable of generating both focal and ambient stimuli depending on the task at hand.;This dissertation represents a first step in creating VAC haptic feedback systems that can convey information to a user at an appropriate level of attentional salience. We demonstrate that a VAC haptic device is able to produce relevant stimuli without unnecessarily competing for a user's limited attentional resources. As with all VAC devices, this allows the haptic device to provide important information to a user in a timely, accurate, and unobtrusive manner.;We begin the exploration of VAC haptic feedback through the specific application of seated posture guidance. This task is a good candidate for VAC haptics as it is typically lower priority and requires minimal cognitive bandwidth. A real-time posture sensing and feedback chair, Posture Seat, was prototyped for this purpose. We created VAC versions of the chair with either vibration or pressure actuators, and a non-VAC version with vibration actuators, to produce the necessary stimuli for haptic feedback. In our initial experiments with the non-VAC Posture Seat, we measured users' ability to comply with postural guidance and their level of mental load while responding to the feedback. We tested various haptic actuator parameters for their influence on affect and attention capture, and integrated these parameters into the design of the vibrotactile and pressure-based VAC Posture Seat versions. Finally, we used the VAC Posture Seat for an in-the-wild study to investigate user compliance, level of mental load, attention capture, and task interference from haptic feedback. We thus were able to assess the impact of our VAC haptic system by comparing the VAC and non-VAC experiments.;Our results represent important findings in the development of VAC haptic systems. We demonstrated that VAC haptic actuators reduced the amount of disruption experienced by subjects compared to those tested on the non-VAC system. We found that actuation rate was the most significant parameter for achieving VAC - i.e., higher actuation rates produced more focal haptic stimuli, while lower actuation rates produced more ambient haptic stimuli. Thus, an increase in the bandwidth of actuator rate resulted in a wider range of attention capture. Actuation intensity was also an important parameter for VAC: increasing the resolution of intensities from sub-threshold to supra-threshold of detectability leads to better VAC. Finally, we found that pressure feedback was more conducive to VAC than vibrotactile feedback, potentially due to the prioritization of the activation of different cutaneous mechanoreceptors. Interestingly many parameters had no significant contribution to VAC due to widely variable user preferences, and thus could be user-defined without loss of VAC capability.;We have successfully designed, characterized, and tested a posture sensing and feedback system employing VAC haptic feedback, including in-the-wild studies for real-time posture correction. We demonstrate that VAC haptic feedback is both feasible and beneficial for modulating information priority and improving task performance in our Posture Seat system, and determined the main parameters for achieving VAC in our system. By quantifying the degree of attention capture in our system and characterizing the necessary parameters for doing so, we lay the foundation for a general approach in developing VAC-capable haptic systems. Our findings form the basis for further developments in VAC haptics that will produce a richness in haptic communication through utilizing the full range of haptic vocabulary, tone, and context.