Utility of prosaccadic eye movements as a response modality in people with severe speech and physical impairments (SSPI)

Traditionally used cognitive-linguistic assessment measures frequently rely on verbal responses, pointing to or manipulation of objects to indicate responses. These response modalities are not feasible for people who have severe speech and physical impairments (SSPI). Reports that eyegaze is a robust alternative response modality are often anecdotal in nature. This experiment aimed to provide evidence that eye gaze tracking is a robust and appropriate alternative response modality for cognitive-linguistic assessment by people with SSPI. A cued attention prosaccade task was carried out as per Posner (1980) using a between groups experimental design with an experimental SSPI group and a neurotypical control group. All participants looked towards visual changes on the screen when they appeared but reaction times differed across groups. Mean time to first fixation (TTF) was significantly slower for the experimental group (p=0.03) overall. This difference was due to the significantly slower mean TTF (p<001) in the second half of the experiment as the mean TTF for the first half was not significantly different across groups (p=0.59). Tracking of eye gaze may therefore be an appropriate alternative response modality for cognitive-linguistic assessment by people with SSPI, but effects of fatigue should be considered when interpreting results.