Input Behavior When Using Two Fingers on a Multi-Touch Device

The purpose of this study is to analyze device input patterns using fingers in multi-touch mode and to derive Fitts’ law for multi-touch methods. Three specific input behaviors—dragging, rotating, and pinching—are investigated. Test participants performed two Fitts’ law experiments, a single-touch experiment using the thumb only and a multi-touch experiment using both the thumb and index finger. Within-subject factorial design was implemented with two levels of touch behavior (single-touch) and three levels of touch behavior (multi-touch), six levels of the index of difficulty (ID), four levels of direction, and two levels of repetition. The results indicate that a revised model of Fitts’ law is more appropriate for the multi-touch mode, achieving R² values above 0.895, and identifying the best nonlinear model among several regression models. The results of this study are used to determine the relationship between ID and movement time in terms of Fitts’ law and to investigate whether this relationship is sufficient to serve as a model to predict movement times. This study contributes to the prediction of movement times for products with multi-touch interfaces.