Abstract：The pupil response and fixation position are important variables in eye movement researches. However, they are susceptive to the disturbance of eye blinks. While most studies only focus on the data missing and fluctuation during blinks, but neglect the more extensive influence of blinks on pupil response and fixation position. Thus, present study aims to precisely examine the impacts of blink on pupil response and fixation position. We recorded the pupil size and fixation position using a video eye tracker, and indentifying the blinks based on these data in a simple prolonged fixation task. The temporal sequence was relined to the onset and end of the detected blinks. We observed a large fluctuation (approximately 12%) in the pupil response, which last approximately 4 seconds after the ending of eye blink. During this period, the pupil size was significantly smaller than the baseline from 300 to 1700 ms (P<FDR005). Meanwhile, the fixation errors induced by blinks amount to approximately 1° within the initial 200 ms after the ending of blinks, which was significantly greater than the baseline(P <FDR005). Moreover, the blinkinduced pupil variation could artificially bias the recorded eye position(with a maximum of 026°in the present study). Our results suggest that the spontaneous blinks affect the pupil size and fixation position to a much larger extent and longer duration than commonly assumed, which should be taken into consideration in the careful explanation of eye movement related experimental results.
［1］Beatty J, LuceroWagoner B. The pupillary system ［J］. Handbook of Psychophysiology, 2000, 2:142-162.
［2］Nassar MR, Rumsey KM, Wilson RC，et al. Rational regulation of learning dynamics by pupillinked arousal systems ［J］. Nature Neuroscience, 2012, 15(7):1040-1046.
［3］Einhauser W, Koch C, Carter O. Pupil dilation betrays the timing of decisions ［J］. Frontiers in Human Neuroscience, 2010, 4:18.
［4］Einhuser W, Stout J, Koch C, et al. Pupil dilation reflects perceptual selection and predicts subsequent stability in perceptual rivalry ［J］. Proceedings of the National Academy of Sciences, 2008, 105(5):1704-1709.
［5］Sheliga B, Riggio L, Rizzolatti G. Orienting of attention and eye movements ［J］. Experimental Brain Research, 1994, 98(3):507-522.
［6］Sheliga B, Riggio L, Rizzolatti G. Spatial attention and eye movements ［J］. Experimental Brain Research, 1995, 105(2):261-275.
［7］Nakano T, Yamamoto Y, Kitajo K, et al. Synchronization of spontaneous eyeblinks while viewing video stories ［J］. Proceedings of the Royal Society B: Biological Sciences, 2009, 276: 3635-3544.
［8］Collewijn H, Van der Steen J, Steinman R. Human eye movements associated with blinks and prolonged eyelid closure ［J］. J Neurophysiol, 1985, 54(1):11-27.
［9］Evinger C, Manning KA, Pellegrini JJ, et al. Not looking while leaping: the linkage of blinking and saccadic gaze shifts ［J］. Experimental Brain Research, 1994, 100(2):337-344.
［10］Fukuda K, Stern JA, Brown TB, et al. Cognition, blinks, eyemovements, and pupillary movements during performance of a running memory task ［J］. Aviation, Space and Environmental Medicine, 2005, 76(Supplement 1):C75-C85.
［11］Hupé JM, Lamirel C, Lorenceau J. Pupil dynamics during bistable motion perception ［J］. Journal of Vision, 2009, 9(7):10.
［12］Siegle GJ, Ichikawa N, Steinhauer S. Blink before and after you think: blinks occur prior to and following cognitive load indexed by pupillary responses ［J］. Psychophysiology, 2008, 45(5):679-687.
［13］Costela F, OteroMillan J, McCamy M, et al. Microsaccades correct fixation errors due to blinks ［J］. Journal of Vision, 2013, 13(9):1335-1335.
［14］Brainard DH. The psychophysics toolbox ［J］. Spatial Vision, 1997, 10:433-436.
［15］Pelli DG. The VideoToolbox software for visual psychophysics: Transforming numbers into movies ［J］. Spatial Vision, 1997, 10(4):437-442.
［16］Savitzky A, Golay MJ. Smoothing and differentiation of data by simplified least squares procedures ［J］. Analytical Chemistry, 1964, 36(8):1627-1639.
［17］Genovese CR, Lazar NA, Nichols T. Thresholding of statistical maps in functional neuroimaging using the false discovery rate ［J］. Neuroimage, 2002, 15(4):870-878.
［18］Bour L, Aramideh M, De Visser BO. Neurophysiological aspects of eye and eyelid movements during blinking in humans ［J］. Journal of Neurophysiology, 2000, 83(1):166-176.［19］Wyatt HJ. The human pupil and the use of videobased eyetrackers ［J］. Vision Research, 2010, 50(19):1982-1988.
［20］Drewes J, Masson GS, Montagnini A. Shifts in reported gaze position due to changes in pupil size: Ground truth and compensation［C］//Proceedings of the Symposium on Eye Tracking Research and Applications. Santa Barbara: ACM, 2012: 209-212.
