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                 | Fixational eye movements do not predict attentional benefits Todd S Horowitz 1,3, Elisabeth M Fine 2,3, David Fencsik 1,3, Sergey Yurgenson 2,3, Jeremy M Wolfe 1,3 1 - Brigham & Women's Hospital Debate about the nature of fixational eye movements (FEMs) has revived recently with the claim that microsaccades reflect the direction of shifts of covert attention (Engbert & Kliegl, 2003; Hafed & Clark, 2002). This work has demonstrated an association between cue direction and microsaccade direction, but are FEMs a reliable marker for the deployment of attention? If so, then if FEMs point to the target location, reaction times (RTs) should be faster than if they point away from the target. We hypothesized that on trials when the cue and FEM directions conflicted, attention would follow the FEM and not the cue. However, this was not the case. We used a dual-Purkinje image eye tracker to measure gaze position of three observers (two authors, one naïve) while they performed an attentional cueing experiment with three different response types: saccadic localization; manual localization; and manual detection. Similar results were obtained across all response conditions for both microsaccades (identified using the Engbert & Kliegl, 2003 algorithm) and drift (measured via average eye position). When FEMs were oriented in the cued direction, standard validity effects were observed. However, when FEMs and cues were oriented in opposite directions, RTs were slower when the FEM pointed towards the target. On uncued trials or trials with neutral cues, FEM direction did not affect RT. Cues, not FEMs, predicted behavior. Fixational eye movements may serve important functions for the visual system. However, they do not reflect the orientation of visual attention. |