The mean point of vergence is biased under projection
The point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We show that the mean point of vergenc...
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MDPI AG
2019-09-01
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| Series: | Journal of Eye Movement Research |
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| Online Access: | https://bop.unibe.ch/JEMR/article/view/4485 |
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| author | Xi Wang Kenneth Holmqvist Marc Alexa |
| author_facet | Xi Wang Kenneth Holmqvist Marc Alexa |
| author_sort | Xi Wang |
| collection | DOAJ |
| description | The point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We show that the mean point of vergence is generally biased for centrally symmetric errors and that the bias depends on the horizontal vs. vertical error distribution of the tracked eye positions. Our analysis continues with an evaluation on real experimental data. The error distributions seem to be different among individuals but they generally leads to the same bias towards the observer. And it tends to be larger with an increased viewing distance. We also provided a recipe to minimize the bias, which applies to general computations of eye ray intersection. These findings not only have implications for choosing the calibration method in eye tracking experiments and interpreting the observed eye movements data; but also suggest to us that we shall consider the mathematical models of calibration as part of the experiment. |
| format | Article |
| id | doaj-art-91cd929a03294ad1b745f2c890f6851f |
| institution | OA Journals |
| issn | 1995-8692 |
| language | English |
| publishDate | 2019-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Journal of Eye Movement Research |
| spelling | doaj-art-91cd929a03294ad1b745f2c890f6851f2025-08-20T01:51:07ZengMDPI AGJournal of Eye Movement Research1995-86922019-09-0112410.16910/jemr.12.4.2The mean point of vergence is biased under projectionXi Wang0Kenneth Holmqvist1Marc Alexa2TU BerlinRegensburg UniversityTU BerlinThe point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We show that the mean point of vergence is generally biased for centrally symmetric errors and that the bias depends on the horizontal vs. vertical error distribution of the tracked eye positions. Our analysis continues with an evaluation on real experimental data. The error distributions seem to be different among individuals but they generally leads to the same bias towards the observer. And it tends to be larger with an increased viewing distance. We also provided a recipe to minimize the bias, which applies to general computations of eye ray intersection. These findings not only have implications for choosing the calibration method in eye tracking experiments and interpreting the observed eye movements data; but also suggest to us that we shall consider the mathematical models of calibration as part of the experiment.https://bop.unibe.ch/JEMR/article/view/4485eye movementeye trackingfixationsgazevergencebias |
| spellingShingle | Xi Wang Kenneth Holmqvist Marc Alexa The mean point of vergence is biased under projection Journal of Eye Movement Research eye movement eye tracking fixations gaze vergence bias |
| title | The mean point of vergence is biased under projection |
| title_full | The mean point of vergence is biased under projection |
| title_fullStr | The mean point of vergence is biased under projection |
| title_full_unstemmed | The mean point of vergence is biased under projection |
| title_short | The mean point of vergence is biased under projection |
| title_sort | mean point of vergence is biased under projection |
| topic | eye movement eye tracking fixations gaze vergence bias |
| url | https://bop.unibe.ch/JEMR/article/view/4485 |
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