Sentence examples for fixation disparity from inspiring English sources
We wondered if the standard deviation of fixation disparity, i.e., the variability in fixation disparity during fixations, was dependent on the position within the text.
Further, we plotted the standard deviation of fixation disparity as function of horizontal fixation position (see Figure 6).
Moreover, for dyslexics the standard deviation of fixation disparity was larger particularly when reading at near distance.
Some studies [5], [25], [27] suggest a correlation with fixation disparity and its stability but this remains controversial.
Interestingly, analyzing the horizontal fixation disparity showed a tendency for an increased fixation disparity for close reading (F1,18 = 3.43, p = 0.08) and a clear tendency for an overall larger fixation disparity for dyslexic children (F1,18 = 3.68, p = 0.07), while these effects did not interact (F-value <1).
Figure 3 shows the probability distributions for the standard deviation of fixation disparity, while the means and ranges can be found in Table 1.
Jaschinski et al. [25] also showed increased variability of fixation disparities during fixations to single targets, when fixation disparities were measured using psychophysical methods.
There are reports that increased fixation disparities coincide with fatigue and eye strain at near vision [21], [22].
We found a slight tendency for larger fixation disparities in dyslexics while reading a real text – in contrast to Jaschinski et al. [25] or Cornelissen et al. [5].
The eye movement signal of the Chronos Eye Tracking system was newly calibrated (monocularly) before each of these two short presentations and we extracted saccade amplitudes, fixation durations, saccade disconjugacies, the discongugate drift in veregnce during fixations as well as fixation disparities and their standard deviations for these presentations as described above (see Methods section).
Another popular method for the correction of eye-tracking data is based on measuring the disparity between each fixation and the closest stimulus on the screen (Zhang & Hornof, 2011).
