Concurrent validation of an eyetracking-based method for assessing attention allocation

Several authors have reported that individuals with aphasia have greater difficulty allocating attention according to task demands than people without neurological disorders (Hula & McNeil, 2008; LaPointe & Erickson, 1991; McNeil et al., 2004; McNeil et al., 2005; Murray, Holland, & Beeson, 1997; Robin & Rizzo, 1988). Studying how attention deficits contribute to neurogenic language deficits is important for clinical practice and research. However, existing methods for indexing attention allocation in people with aphasia pose serious methodological challenges, including demands on comprehension abilities for understanding of dual-task instructions prior to an experiment, and response requirements that may impact participants’ performance. Eyetracking methods have great potential to address such challenges. Such methods do not require a) understanding of complex instructions; b) responding verbally, in writing, or with gestures; or c) manipulating devices, such as a computer mouse or joystick (Hallowell, Wertz, & Kruse, 2002). These features reduce critical response confounds and improve the validity of assessment tools for indexing attention allocation (Heuer & Hallowell, 2013). Heuer and Hallowell (2013) developed an eyetracking method to assess attention allocation using a dual-task paradigm in individuals with and without aphasia. The dual-task method included a visual search task, in which participants were trained to find a visual target in a display that included one target and three nontarget foils, and an auditory linguistic processing task, in which sentences were presented auditorally. Attention demands were manipulated by varying the complexity of each of the two tasks. Changes in attention demands were indexed through performance on the visual search task using eyetracking measures. Results indicated that the method is sensitive to differences between people with and without aphasia, and that it captures response variations associated with task demands and stimulus complexity. While those results were valuable in establishing the construct validity of the novel eyetracking-based measures, no conclusions could be drawn about the concurrent validity of the method because no previously validated measure of attention allocation had been administered