Abstract
Gaze-based text spellers have proved useful for people with severe motor diseases, but lack acceptance in general human-computer interaction. In order to use gaze spellers for public displays, they need to be robust and provide an intuitive interaction concept. However, traditional dwell- and blink-based systems need accurate calibration which contradicts fast and intuitive interaction. We developed the first gaze speller explicitly utilizing smooth pursuit eye movements and their particular characteristics. The speller achieves sufficient accuracy with a one-point calibration and does not require extensive training. Its interface consists of character elements which move apart from each other in two stages. As each element has a unique track, gaze following this track can be detected by an algorithm that does not rely on the exact gaze coordinates and compensates latency-based artefacts. In a user study, 24 participants tested four speed-levels of moving elements to determine an optimal interaction speed. At 300 px/s users showed highest overall performance of 3.34 WPM (without training). Subjective ratings support the finding that this pace is superior.
Highlights
Gaze interaction was used initially to provide a modality of communication for physically impaired users (Majaranta & Raiha, 2002)
The accuracy of the factory default calibration was not sufficient to distinguish the central idle area as the distance was above 80 px, which exceeds the radius of the idle area
We investigated the influence of object movement speed on text entry rate, error rate and perceived subjective quality of the interaction
Summary
Gaze interaction was used initially to provide a modality of communication for physically impaired users (Majaranta & Raiha, 2002). There are drawbacks associated with gaze interaction, involuntary interaction and the need for individual calibration. If the same modality is used for perception and interaction, involuntary input activation is likely to happen. In gaze interaction, this is known as Midas Touch Problem and refers to the legendary king Midas, who wished that everything he touched would be turned into gold, but finds himself trapped in his wish (Jacob, 1991). As gaze is used permanently to gather information, interaction via the same modality holds a high risk of inadvertent user input. Strategies to avoid the Midas Touch Problem need to be considered in interaction design, as well as the implementation of differentiated and easy-to-comprehend feedback (Majaranta, 2011)
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