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In human factors and ergonomics research, the analysis of eye movements has gained popularity as a method for obtaining information concerning the operator's cognitive strategies and for drawing inferences about the cognitive state of an individual. For example, recent studies have shown that the distribution of eye fixations is sensitive to variations in mental workload-dispersed when workload is high, and clustered when workload is low. Spatial statistics algorithms can be used to obtain information about the type of distribution and can be applied over fixations recorded during small epochs of time to assess online changes in the level of mental load experienced by the individuals. In order to ease the computation of the statistical index and to encourage research on the spatial properties of visual scanning, A Simple Tool for Examining Fixations has been developed. The software application implements functions for fixation visualization, management, and analysis, and includes a tool for fixation identification from raw gaze point data. Updated information can be obtained online at www .astef.info, where the installation package is freely downloadable.
This article describes the capabilities of A Simple Tool for Examining Fixations (ASTEF), an offline data analysis application for processing eye-movement information. The tool was developed for specific needs in human factors and ergonomics (HFfE) research, because the analysis of individuals' visual behavior has become increasingly popular in this field.
The path drawn by the eyes during the exploration (or scanning) of a scene has been dubbed scanpath (Noton & Stark, 1971)-a sequence of successive fixations and saccades (between fixations). Seminal work (e.g., Ellis & Smith, 1985; Ponsoda, Scott, & Findlay, 1995; Stark & Ellis, 1981) has been carried out for obtaining information about the visual search strategies that are possibly linked to variations in task demands. However, these studies have failed to show any computable effect of task complexity on visual scanning behavior. Nevertheless, the analysis of scanpath is still popular (e.g., Diez et al., 2001 ; Van Orden, Limbert, Makeig, & Jung, 2001) and is considered to be a valuable method for obtaining information concerning the operator's strategies (e.g., about the areas of an interface that are inspected). Also, as recently stated by McCarley and Kramer (2007), oculomotor data can be used to draw inferences about the...