Design and Effect of Continuous Wearable Tactile Displays

Our sense of touch is one of our core senses and while not as information rich as sight and hearing, it tethers us to reality.
Our skin is the largest sensory organ in our body and we rely on it so much that we don't think about it most of the time.
Tactile displays - with the exception of actuators for notifications on smartphones and smartwatches - are currently understudied and underused.
Currently tactile cues are mostly used in smartphones and smartwatches to notify the user of an incoming call or text message.
Specifically continuous displays - displays that do not just send one notification but stay active for an extended period of time and continuously communicate information - are rarely studied.
This thesis aims at exploring the utilization of our vibration perception to create continuous tactile displays.
Transmitting a continuous stream of tactile information to a user in a wearable format can help elevate tactile displays from being mostly used for notifications to becoming more like additional senses enabling us to perceive our environment in new ways.
This work provides a serious step forward in design, effect and use of continuous tactile displays and their use in human-computer interaction.
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The main contributions include:

Exploration of Continuous Wearable Tactile Interfaces
This thesis explores continuous tactile displays in different contexts and with different types of tactile information systems. The use-cases were explored in various domains for tactile displays - Sports, Gaming and Business applications. The different types of continuous tactile displays feature one- or multidimensional tactile patterns, temporal patterns and discrete tactile patterns.

Automatic Generation of Personalized Vibration Patterns
In this thesis a novel approach of designing vibrotactile patterns without expert knowledge by leveraging evolutionary algorithms to create personalized vibration patterns - is described. This thesis presents the design of an evolutionary algorithm with a human centered design generating abstract vibration patterns. The evolutionary algorithm was tested in a user study which offered evidence that interactive generation of abstract vibration patterns is possible and generates diverse sets of vibration patterns that can be recognized with high accuracy.

Passive Haptic Learning for Vibration Patterns
Previous studies in passive haptic learning have shown surprisingly strong results for learning Morse Code. If these findings could be confirmed and generalized, it would mean that learning a new tactile alphabet could be made easier and learned in passing. Therefore this claim was investigated in this thesis and needed to be corrected and contextualized. A user study was conducted to study the effects of the interaction design and distraction tasks on the capability to learn stimulus-stimulus-associations with Passive Haptic Learning. This thesis presents evidence that Passive Haptic Learning of vibration patterns induces only a marginal learning effect and is not a feasible and efficient way to learn vibration patterns that include more than two vibrations.

Influence of Reference Frames for Spatial Tactile Stimuli
Designing wearable tactile stimuli that contain spatial information can be a challenge due to the natural body movement of the wearer. An important consideration therefore is what reference frame to use for spatial cues. This thesis investigated allocentric versus egocentric reference frames on the wrist and compared them for induced cognitive load, reaction time and accuracy in a user study. This thesis presents evidence that using an allocentric reference frame drastically lowers cognitive load and slightly lowers reaction time while keeping the same accuracy as an egocentric reference frame, making a strong case for the utilization of allocentric reference frames in tactile bracelets with several tactile actuators.