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Sara Giovagnoli, Roberto Bolzani, Tony Pansell, Mariagrazia Benassi; Border enhancing flicker effect in form-from-motion test. Journal of Vision 2018;18(10):294. doi: 10.1167/18.10.294.
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The form-from-motion tests are often done by means of dots moving in two different, sometime opposite, directions inside and outside the form. Generally, the dots disappear when they cross the form border and reappear in some other place depending on the previous position to maintain the same dots density. Grossman and Blake (1999), to avoid the border enhancement due to the luminance flickering, set up a stimulus based on dots not disappearing on the form border. The stimulus is done by dots moving diagonally outside the form and changing randomly to a ±30° deviated direction when the dots enter a virtually defined form. Experiment 1 To check the accuracy difference between the border crossing and non-crossing condition, 21 subjects are tested using two stimuli: one like the Grossman stimulus and the other having the same characteristics but not allowing the dots to cross the border. They disappear and reappear outside or inside the form depending on the original place. The difficulty level is changed decreasing the number of the dots moving in deviated direction inside the form. Results 1 The results showed a significantly different accuracy (p < .001) at all the difficulty levels with a better accuracy in non-crossing condition. Experiment 2 To see if the border flickering effect alone can elicit the form perception, a second experiment is done on the same subjects with the stimulus made by diagonally moving dots both inside and outside the form but disappearing when they cross the border. Results 2 All the subjects have been able to correctly detect the form at least in the lowest difficulty level. Conclusion A form-from-motion test using dots disappearing on the border does not measure the form perception due only to the motion contrast effect but that due also to the border flickering effect.
Meeting abstract presented at VSS 2018
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