Eskenazi, Michael A. "Best practices for cleaning eye movement data in reading research." Behavior Research Methods (2023): 1-11.
Fixation merging methods were first developed by pioneering researcher Keith Rayner at his UMass eye tracking labs. These methods have been passed down through generations of research training and have made their way into eye-movement processing software as default settings (e.g., Data Viewer from SR Research). There are three stages in the fixation merging process. In the first stage, fixations less than 80 ms are merged with a longer fixation within .50 degrees of visual angle. In the second stage, fixations less than 40 ms are merged with a longer fixation within 1.25 degrees of visual angle. Finally, in the third stage, three fixations of 140 ms or less within a single interest area are merged together. I attempted to determine the original justification for these values by contacting SR Research Support who said that they do not take a position on whether these values and this method should be used but that they were included in the program at the request of an eye tracking researcher. I contacted her to determine the origin and she noted that they came from Keith Rayner’s original work. I next contacted several prominent eye tracking researchers who were trained by or worked closely with Keith Rayner, and though they all kindly responded, none of them could provide any specific justification for why these values were selected. Thus, although these values are commonly used as one of the steps to clean fixations, their origin and justification remain unclear.
Eskenazi, Michael A. "Best practices for cleaning eye movement data in reading research." Behavior Research Methods (2023): 1-11.
Fixation merging methods were first developed by pioneering researcher Keith Rayner at his UMass eye tracking labs. These methods have been passed down through generations of research training and have made their way into eye-movement processing software as default settings (e.g., Data Viewer from SR Research). There are three stages in the fixation merging process. In the first stage, fixations less than 80 ms are merged with a longer fixation within .50 degrees of visual angle. In the second stage, fixations less than 40 ms are merged with a longer fixation within 1.25 degrees of visual angle. Finally, in the third stage, three fixations of 140 ms or less within a single interest area are merged together. I attempted to determine the original justification for these values by contacting SR Research Support who said that they do not take a position on whether these values and this method should be used but that they were included in the program at the request of an eye tracking researcher. I contacted her to determine the origin and she noted that they came from Keith Rayner’s original work. I next contacted several prominent eye tracking researchers who were trained by or worked closely with Keith Rayner, and though they all kindly responded, none of them could provide any specific justification for why these values were selected. Thus, although these values are commonly used as one of the steps to clean fixations, their origin and justification remain unclear.