In addition to language impairments, individuals with aphasia frequently have difficulties allocating attention that contribute to language processing, as it has been assessed repeatedly using dual-task experiments. The goal of this study was to develop a method to assess attention allocation during auditory linguistic processing using eye tracking in a dual-task paradigm.
A dual-task experiment included an auditory linguistic processing task, in which sentences were presented auditorily, and 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. 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 eye-tracking measures. Thirty-three adults with aphasia participated and 34 adults free of neurogenic impairments served as control participants.
Significant increases in attention demands were observed from single- to dual-task conditions and from simple to complex verbal and visual stimulus processing, indicated through decreases in the following eye-tracking measures: proportion of fixation duration on the target (PFDT), proportion of number of fixations on the target (PNFT), average fixation on the target (AFDT), first-pass gaze duration on the target (FPGDT); and latency until first fixation on the target (LFFT). Significant differences between participant groups indicated that individuals with aphasia have greater difficulty allocating attention properly according to task demands on linguistic and nonlinguistic tasks. These results are consistent with findings described in other studies indicating that individuals with aphasia have significantly greater difficulty than controls in allocating attention. PFDT and PNFT most consistently indexed changes in attention allocation. Correlations between aphasia severity as indexed by the aphasia quotient from the revised Western Aphasia Battery (WAB-R, Kertesz, 2007) and eye-tracking measures were nonsignificant, suggesting that attention allocation is a cognitive process dissociated from language comprehension. Results support the validity of a novel eye-tracking method as a tool to assess attention allocation in individuals with and without aphasia.