Multimodality During Fixation—Part II: Evidence for Multimodality in Spatial Precision-Related Distributions and Impact on Precision Estimates
Abstract
:Introduction
Some studies have even larger amplitude criteria [see (Poletti & Rucci, 2016)]. Other authors choose 30 min arc, (0.5 deg) as a threshold (Poletti & Rucci, 2016). For purposes of the present analysis, any saccade < 0.5 deg was considered a microsaccade.“Microsaccades were distinguished from macrosaccades using an amplitude threshold of 1° (Martinez-Conde, Otero-Millan, & Macknik, 2013), and the median microsaccade amplitude was 0.65° (M1: 0.71°, M2: 0.65°, M3: 0.62°). This is larger than in most studies, although there is also considerable variability between the average microsaccade amplitudes described in past reports, which include 0.8° (Bair & O'Keefe, 1998), 0.73° (Guerrasio, Quinet, Buttner, & Goffart, 2010), 0.67° (Snodderly, Kagan, & Gur, 2001), 0.46° (Otero-Millan et al., 2011), 0.33° (Ko, Poletti, & Rucci, 2010), and 0.23° (Hafed, Goffart, & Krauzlis, 2009).”.(Arnstein, Junker, Smilgin, Dicke, & Thier, 2015)
Methods
The Eye-Tracking Database
The Signal Processing Steps
Removing Average Saccade Latency
Which Part of Fixation to Analyze
Removing “Blink saccades”
Removing Saccades - Step 1
Removing Saccades - Step 2
Removal of Anticipatory Saccades
Evaluation of the Success of These Efforts to Remove Non-Fixation Samples
Inclusion Criteria for Fixations
Assessing Unimodality
Precision Metric Names
Results
Characteristics of Accepted Fixations
Bayes Factor Distribution
Histogram of Number of Components
Distributions of Measures of Precision
Oculomotor Basis for Multimodality
Discussion
“If histograms and probability plots indicate that your data are in fact reasonably approximated by a normal distribution, then it makes sense to use the standard deviation as the estimate of scale. However, if your data are not normal, and in particular if there are long tails, then using an alternative measure such as the median absolute deviation, average absolute deviation, or interquartile range makes sense.” Link to Textbook Page (NIST/SEMATECH, 2012)
Ethics and Conflict of Interest
Acknowledgments
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Step 1 | Remove saccade latency |
Step 2 | Choose a portion of each fixation to analyze for precision |
Step 3 | Remove blink saccades |
Step 4 | Remove saccades – step 1 |
Step 5 | Remove saccades, etc. - step 2 |
Step 6 | Remove anticipatory saccades |
Direction | N Events | % Unimodal * | % Positive † | % Strong ‡ | % Very Strong $ |
Horiz. | 14,087 | 20.8 | 4.4 | 5.1 | 69.7 |
Vert. | 14,087 | 23.2 | 4.6 | 4.6 | 67.5 |
*-No evidence of multimodality [log(BF) <= 1] | |||||
†-Positive evidence of multimodality [log(BF) > 1 & log(BF)<=3] | |||||
‡-Strong evidence of multimodality [log(BF) > 3 & log(BF)<=5] | |||||
$-Very strong evidence of multimodality [log(BF) > 5] |
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Friedman, L.; Hanson, T.; Komogortsev, O.V. Multimodality During Fixation—Part II: Evidence for Multimodality in Spatial Precision-Related Distributions and Impact on Precision Estimates. J. Eye Mov. Res. 2021, 14, 1-9. https://doi.org/10.16910/jemr.14.3.4
Friedman L, Hanson T, Komogortsev OV. Multimodality During Fixation—Part II: Evidence for Multimodality in Spatial Precision-Related Distributions and Impact on Precision Estimates. Journal of Eye Movement Research. 2021; 14(3):1-9. https://doi.org/10.16910/jemr.14.3.4
Chicago/Turabian StyleFriedman, Lee, Timothy Hanson, and Oleg V. Komogortsev. 2021. "Multimodality During Fixation—Part II: Evidence for Multimodality in Spatial Precision-Related Distributions and Impact on Precision Estimates" Journal of Eye Movement Research 14, no. 3: 1-9. https://doi.org/10.16910/jemr.14.3.4
APA StyleFriedman, L., Hanson, T., & Komogortsev, O. V. (2021). Multimodality During Fixation—Part II: Evidence for Multimodality in Spatial Precision-Related Distributions and Impact on Precision Estimates. Journal of Eye Movement Research, 14(3), 1-9. https://doi.org/10.16910/jemr.14.3.4