A binocular moving window technique to study the roles of the two eyes in reading

Monocular Versus Binocular Calibrations in Evaluating Fixation Disparity With a Video-Based Eye-Tracker

“…However, our results show a large range of the monocularly calibrated fixation disparities compared with a smaller range of the binocularly calibrated fixation disparities. Our findings provide direct support for the arguments of Nuthmann and coworkers (Nuthmann, Beveridge, & Shillcock, 2014;Nuthmann and Kliegl, 2009). In both their studies, participants read single sentences, but Nuthmann et al used a monocular calibration and the EyeLink 1000, while Nuthmann and Kliegl used a binocular calibration and both the EyeLink I and the EyeLink II.…”

“…In this study, as well as others, the visual task in question, whether it is a reading task or a dot scanning task, and so forth, may be relevant. In the course of reading one line, a series of fixations and corresponding rightward saccades are made, and, when black stimuli are presented on a white background, the fixation disparity shifts toward the eso direction, for both monocular and binocular calibrations (Jainta, Hoormann et al, 2010;Jainta, Jaschinski, & Wilkins, 2010;Nuthmann et al, 2014;Nuthmann & Kliegl, 2009). However, clearly exo fixation disparity is observed when viewing white stimuli on a black background (Blythe et al, 2006;Juhasz, Liversedge, White, & Rayner, 2006;Kirkby et al, 2010Kirkby et al, , 2013.…”

“…But other cases may occur, depending on the individual and the viewing conditions. This theoretical background explains the reason for the general consensus among researchers to apply a monocular calibration in fixation disparity studies (Jainta, Hoormann, et al, 2010;Jainta & Kapoula, 2011;Jaschinski et al, 2010;Kirkby et al, 2013;Kirkby, Webster, Blythe, & Liversedge, 2008;Liversedge, 2008;Liversedge, Rayner, White, Findlay, & McSorley, 2006;Nuthmann, Beveridge, & Shillcock, 2014;Tyler, Elsaid, Likova, Gill, & Nicholas, 2012). Some debates still exist-is there really a difference between monocularly calibrated and binocularly calibrated fixation disparities?…”

Do pupil-based binocular video eye trackers reliably measure vergence?

“…In most studies this is not seen as a difficult problem and the question is simply solved by intersecting the line of sight from one of the two eyes with the closest object in front of the observer that occludes the background. For example in the field of reading, researchers approach the question of where the fixation is located in the 3-D world (namely a fixation on a 2D screen with text) by assuming that the two eyes look on the same point on the screen 1 (Nuthmann, Beveridge, & Shillcock, 2014). Therefore, reading researchers often use eye tracking data from only one eye (the right eye) during binocular viewing (e.g.…”

Pupil size affects measures of eye position in video eye tracking: implications for recording vergence accuracy

“…Research on fixation disparity in reading and nonreading tasks (e. g., Kirkby, Webster, Blythe, & Liversedge, 2008;Jainta, Hoormann, Kloke, & Jaschinski, 2010;Jainta, Jaschinski, & Wilkins, 2010;Nuthmann, Beveridge, & Shillcock, 2014) has shown that fixation disparity is typically below 1 deg. This small amount is at the limit of the accuracy of video-based eye trackers so that any effort for high accuracy recording is required and the pupil artefact should be considered as a source of error.…”