No abstract

A barrier to practical use of electrotactile stimulation for haptic feedback has been large variability in perceived sensation intensity due to changes in the impedance of the electrode-skin interface, such as when electrodes peel or users sweat. Here, we show how to significantly reduce this variability by modulating stimulation parameters in response to measurements of impedance. Our method derives from three contributions. First, we created a model between stimulation parameters and impedance at constant perceived sensation intensity by looking at the peak pulse energy and phase charge. Our model fits experimental data better than previous models (mean R2 > 0.9) and holds over a larger set of conditions (subjects, sessions, magnitudes of sensation, stimulation locations, electrode sizes). Second, we implemented a controller that regulates perceived sensation intensity by using our model to derive a new current amplitude and pulse duration in response to changes in impedance. Our controller accurately predicts subject-chosen stimulation parameters at constant sensation intensity (mean R2 > 0.9). Third, we demonstrated as a proof-of-concept on two subjects with below-elbow amputations—using a prosthesis with electrotactile touch feedback—that our controller can regulate sensation intensity in response to large impedance changes that occur in activities of daily living. These results make electrotactile stimulation for human-machine interfaces more reliable during activities of daily living.

No abstract

Electrotactile stimulation is a common method of sensory substitution and haptic feedback. One problem with this method has been the large variability in perceived sensation that derives from changes in the impedance of the electrode-skin interface. One way to reduce this variability is to modulate stimulation parameters (current amplitude and pulse duration) in response to impedance changes, which are reflected in the time domain by changes in measured peak resistance, R p . To work well, this approach requires knowing precisely the relationship between stimulation parameters, peak resistance, and perceived sensation. In this paper, experimental results show that at a constant level of perceived sensation there are linear relationships between R p and both peak pulse energy, E p , and phase charge, Q, from which stimulation parameters are easily computed. These linear relationships held across different subjects, sessions, magnitudes of sensation, stimulation locations, and electrode sizes. The average R 2 values for these linear relationships were 0.957 for E p vs. R p and 0.960 for Q vs. R p , indicating a nearly perfect fit.

Despite evidence that a majority of people in the United States say that they want more civil politics, candidates still use incivility strategically during campaigns. Distinguishing between descriptive and injunctive norms may help explain this apparent contradiction. This study presents an experiment conducted with participants recruited at 2020 Democratic Iowa Caucus rallies that tested whether (a) individuals differ in their descriptive and injunctive normative beliefs about a variety of uncivil behaviors and (b) candidate characteristics such as gender and insider/outsider status in a party influence respondents’ normative beliefs. Findings suggest that, while descriptive and injunctive norms align for some campaign behaviors, they do not for all behaviors, such as sharing false information and using insults. Additionally, men and women candidates, as well as political insider and outsider candidates, are expected to behave differently but are held to the same injunctively normative standard when uncivil behaviors are attributed to them. Future incivility researchers should continue investigating descriptive and injunctive norms to investigate whether voters dismiss descriptively common behaviors during campaigns, even if they perceive those behaviors as inappropriate and uncivil.