Graduation Year

2021

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Mechanical Engineering

Major Professor

Kyle Reed, Ph.D.

Committee Member

Rasim Guldiken, Ph.D.

Committee Member

Kristen Salomon, Ph.D.

Committee Member

Yasin Yilmaz, Ph.D.

Committee Member

Miguel Goni Rodrigo, Ph.D.

Keywords

Emotions, Haptic Memory, Haptics, Human Thermal Perception, Human-Computer Interaction, Temperature

Abstract

Haptics is an interdisciplinary field of science that deals with how humans perceive and respond to different sensory cues perceived through touch. Thermal haptics as a branch deals with how humans perceive the temperature sensation and respond to that. The process in which thermal perception occurs is well known to researchers. What seems missing in the literature is how temperature interacts or sometimes intervenes in other physiological and psychological aspects of our lives. In this research, a series of studies are presented where the main focus was how temperature and brain interact with each other to impede or enhance our perceptions or our performance when dealing with temperature.

Asymmetric thermal stimulation methods have been introduced previously where a combination of rapidly changing and slowly changing temperatures was creating a constant cooling/warming perception. To increase the intensity of this perception, a new dynamically changing thermal pattern was implemented, which resulted in the discovery of a counter-intuitive thermal sensation where cooling patterns were creating a warming sensation, and warming patterns were creating a cooling sensation at some skin temperature ranges. In this study, the idea of a thermal neutral zone was another subject of investigation. There can be three definitions of the thermal neutral point based on conventional skin temperature, measured skin temperature, and measured neutral zone. In this study, the counter-intuitive effect was observed in all three cases.

In another effort to understand the interaction between temperature and the brain, we investigated the contribution of thermal cues on emotional states. Using a custom-built wearable thermal actuator, and a graphical user interface, and well-established methods in the field of psychology, we aimed to evaluate how different temperature conditions affected individuals' self-report of their emotions. The results indicated that warm and cold temperature conditions were able to change the arousal levels of the emotions but not the valence.

To continue the research path on the investigation of the interaction between temperature and perception, a memory game was developed that was inspired by the "Simon Says" game. This study evaluates sensory memory when visual and haptic cues contain a combination of spatial and modality information presented to the users. The results indicated that humans can retain between five to eight cues in memory when given a sequence of stimuli. Haptic memory is demonstrated to perform worse than visual memory while behaving similarly in some modes depending on the provided information. As a result of this research, a difficulty scoring system for multiple spatial patterns was developed using survey and experimental results.

In an extension to the previous path of investigation, another aspect of human memory was evaluated in the presence of time delay, also known as Inter-Stimulus Interval (ISI). The effect of ISI on thermal discrimination ability, Just Noticeable Difference (JND), can be a baseline for the designers of wearable haptic devices to deliver easily interpretable cues to the users. In this study, individuals were given two thermal cues to compare. This way, their thermal discrimination ability was determined in each case. This procedure resulted in an average thermal JND of 3.50 C without delay (ISI=0) and an increase in thermal JND value by 11.9% and 21.2% at 3 and 9 seconds ISI.

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