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Fixation density as a function of fixation serial order. (A) Eye. (B) Mouth. (C) Center. (D) Area not in any of the ROI. Shaded area denotes one SEM across subjects. Asterisks indicate significant difference using two-tailed paired t-test (uncorrected). +P < 0.1, *P < 0.05, and **P < 0.01.
