Cite as:
Rolfs M, Engbert R, Kliegl R, 2004, "Perception and motor control: The link between fixational eye movements and postural sway" Perception 33 ECVP Abstract Supplement

Perception and motor control: The link between fixational eye movements and postural sway

M Rolfs, R Engbert, R Kliegl

During fixation, eye position is imperceptibly altered by small involuntary eye movements. Two important types of these 'fixational' eye movements (FEMs) are drift and microsaccades. Recently, we investigated statistical behaviour of FEMs using a random-walk analysis (Engbert and Kliegl, 2004 Psychological Science 15 431 - 435). Scaling exponents obtained by this analysis indicated a separation of time scales in FEMs. Here, we investigate how microsaccades interact with postural sway in three conditions: sitting with the head positioned on a chin-rest, normal sitting, and standing. Using the same analysis, we replicated the findings of our first study in the sitting with chin-rest condition: microsaccades enhance fixation errors on a short time scale, a phenomenon known as persistence and control fixation errors on a longer time scale (antipersistence). On the short time scale, scaling exponents are very similar across conditions. On the long time scale, fewer fixation errors can be observed (more antipersistence), although postural sway contributes to the noise level in gaze position. The interaction of FEMs with postural control indicates a global coupling of perceptual motor systems. FEMs constitute visual fixation, the platform on which almost all visual perception depends -- understanding their properties has potential impact on fundamental mechanisms of perception.

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