K.K. Driller
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From Cue to Construct
Cues, Mechanisms, and Stability in Haptic Perception
This dissertation addresses how we reconstruct perceptual representations from the mechanical inputs that occur during haptic interactions. It focuses on the behaviorally relevant information that allows the somatosensory system to achieve its goals, such as enabling the exploration and dexterous manipulation of objects.
The dissertation covers fundamental concepts related to the emergence of stable haptic percepts and presents a series of experimental studies spanning topics from contact detection, through texture and material perception, to the perception of time during haptic interactions. The studies reveal several fundamental mechanisms in haptic perception: an intensity metamer in impact detection where duration and amplitude trade off, the role of propagating vibratory waves for roughness perception, and roughness metamers where different combinations of elasticity and surface features produce identical percepts.
Using a novel dual-property stimulus database and local anesthesia techniques, the work further highlights the crucial role of cutaneous information in softness perception and shows how the lack of cutaneous information can influence the perceived timing of haptic interactions.
Together, the studies uncover essential cues and mechanisms used to perceptually reconstruct different haptic interactions. ...
This dissertation addresses how we reconstruct perceptual representations from the mechanical inputs that occur during haptic interactions. It focuses on the behaviorally relevant information that allows the somatosensory system to achieve its goals, such as enabling the exploration and dexterous manipulation of objects.
The dissertation covers fundamental concepts related to the emergence of stable haptic percepts and presents a series of experimental studies spanning topics from contact detection, through texture and material perception, to the perception of time during haptic interactions. The studies reveal several fundamental mechanisms in haptic perception: an intensity metamer in impact detection where duration and amplitude trade off, the role of propagating vibratory waves for roughness perception, and roughness metamers where different combinations of elasticity and surface features produce identical percepts.
Using a novel dual-property stimulus database and local anesthesia techniques, the work further highlights the crucial role of cutaneous information in softness perception and shows how the lack of cutaneous information can influence the perceived timing of haptic interactions.
Together, the studies uncover essential cues and mechanisms used to perceptually reconstruct different haptic interactions.
Temporal binding refers to a systemic bias in the perceived time interval between two related events, most frequently voluntary motor actions and a subsequent sensory effect. An inevitable component of most instrumental motor actions is tactile feedback. Yet, the role of tactile feedback within this phenomenon remains largely unexplored. Here, we used local anesthesia of the index finger to temporarily inhibit incoming sensory input from the finger itself, while participants performed an interval-estimation task in which they estimated the delay between a voluntary motor action (button press) and a second sensory event (click sound). Results were compared to a control condition with intact sensation. While clear binding was present in both conditions, the effect was significantly enhanced when tactile feedback was temporarily removed via local anesthesia. The results are discussed in light of current debates surrounding the underlying mechanisms and function of this temporal bias.
Ultrasound mid-air haptic (UMH) devices are a novel tool for haptic feedback, capable of providing localized vibrotactile stimuli to users at a distance. UMH applications largely rely on generating tactile shape outlines on the users' skin. Here we investigate how to achieve sensations of continuity or gaps within such two-dimensional curves by studying the perception of pairs of amplitude-modulated focused ultrasound stimuli. On the one hand, we aim to investigate perceptual effects that may arise from providing simultaneous UMH stimuli. On the other hand, we wish to provide perception-based rendering guidelines for generating continuous or discontinuous sensations of tactile shapes. Finally, we hope to contribute toward a measure of the perceptually achievable resolution of UMH interfaces. We performed a user study to identify how far apart two focal points need to be to elicit a perceptual experience of two distinct stimuli separated by a gap. Mean gap detection thresholds were found at 32.3-mm spacing between focal points, but a high within- and between-subject variability was observed. Pairs spaced below 15 mm were consistently (>95%) perceived as a single stimulus, while pairs spaced 45 mm apart were consistently (84%) perceived as two separate stimuli. To investigate the observed variability, we resort to acoustic simulations of the resulting pressure fields. These show a non-linear evolution of actual peak pressure spacing as a function of nominal focal point spacing. Beyond an initial threshold in spacing (between 15 and 18 mm), which we believe to be related to the perceived size of a focal point, the probability of detecting a gap between focal points appears to linearly increase with spacing. Our work highlights physical interactions and perceptual effects to consider when designing or investigating the perception of UMH shapes.
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