Modeling Movement Times and Success Rates for Acquisition of One-dimensional Targets with Uncertain Touchable Sizes

Abstract

In touch interfaces, a target, such as an icon, has two widths: the visual width and the touchable width. The visual width is the target's appearance, and the touchable width is the area in which users can touch a target and execute an action. In this study, we conduct two experiments to investigate the effects of the visual and touchable widths on touch pointing performance (movement time and success rate). Based on the results, we build candidate models for predicting the movement time and compare them by the values of adjusted R^2 and AIC. In addition, we build a success rate model and test it through cross-validation. Existing models can be applied only to situations where the visual and touchable widths are equal, and we show that our refined model achieves better model fitness, even when such widths are different. We also discuss the design implications of the touch interfaces based on our models.

Independent influences of movement distance and visual distance on Fitts’ law.

“…Incentives also modulate movement durations (Ashworth-Beaumont & Nowicky, 2013; Bogacz et al, 2010; Du et al, 2022; Listman et al, 2021; Thura et al, 2014), further supporting flexibility in the strategies the brain employs when selecting movement parameters. We also note that other studies of Fitts’ Law in virtual environments, where visual and physical dimensions of the target do not necessarily match, largely align with our results in showing that both the visual and motor dimensions can predict movement durations under specific contexts (Usuba et al, 2019, 2021). Future investigations can address other, perhaps more cognitive indicators of difficulty, such as the visually inferred weight or unwieldiness of a tool (Ellis & Lederman, 1993).…”