Task relevance moderates saccade velocities to spatially separated cues

Task relevance moderates saccade velocities to spatially separated cues Caitlyn M. McColeman (caitlyn_mccoleman@sfu.ca) Department of Psychology, Simon Fraser University 8888 University Drive, Burnaby, BC V5A 1S6 Mark R. Blair (mark_blair@sfu.ca) Cognitive Science Program & Department of Psychology, Simon Fraser University 8888 University Drive, Burnaby, BC V5A 1S6 Abstract The study of eye movements has enjoyed a history of supporting theories of attention in different task settings by expanding our understanding of how people navigate tasks such as natural scene perception, reading and categorization. The theories and models that these data inform, however, are largely based on fixation patterns. Presently lacking is an understanding of how the eye movements preceding these fixations are affected by the task environment and if they change as a function of a shift in the state of knowledge. In an effort to close this gap, we report changing saccade velocities in two category learning experiments, evidencing the importance of understanding saccades in developing a stronger theory of the deployment of visual attention as it is influenced by higher level cognitive changes. Keywords: Saccades; eye movements; category learning; visual attention; learning The visual world contains an enormous amount of information. From when we wake up to check the time, to the familiar walk to the car, we make a remarkable number of eye movements to different elements of the environment in order to extract the information that is relevant to our goals at the time. However, we also make a large number of eye movements to elements of the environment that are irrelevant to our goals. For instance, the tree rustling outside the kitchen window is unrelated preparing a coffee, but we still opt to look there from time-to-time during the morning ritual. These eye movements, saccades, are punctuated by fixations. During fixations, the eyes pause while extracting information from the environment for further processing. The saccade itself is not an effective source of information gathering, since visual perception is suppressed while the eye is in motion (Matin, 1974). However, the fixation is unable to gather information from another part of the environment without the preceding saccade to bring the eye to the target location. Since so many saccades are made each minute, small differences in the speed or accuracy of the movement can add up to important cumulative differences in completing a task or perceiving various parts of the visual environment. It is both the journey and the destination of the eye, on the scale of milliseconds, that indicate the processing underlying the deployment of visual attention. The subtle properties of saccades have been explored in oculomotor learning tasks, wherein participants are trained to saccade toward a target. Work in non-human primates has shown that saccades quicken when they are deployed to a rewarded target location relative to alternative unrewarded locations (Takikawa, Kawagoe, Itoh, Nakahara & Hikosaka, 2002), implicating an important role of learning and reinforcement in programming and executing saccades. In an anti-saccade task, when the participants’ goal is to make a saccade to the mirror location of an onscreen cue, saccades tend to be longer and are more likely to miss the target location than when the task is simply to make a saccade to a cue (Hallett, 1977; Walker, Walker, Husain & Kennard, 2002). Recent work shows eye movements in the anti-saccade task can be further affected by factors such as drowsiness (Ahlstrom, Nystrom et al. 2013), age and executive function (Mirsky, Heuer, Jafari, Kramer, Schenk, Viskontas, Miller, & Boxer, 2011), alcohol impairment (Roche & King, 2010) and anxiety (Cornwell, Mueller, Kaplan, Grillon, & Ernst, 2012). Through the variety of sampled participants, it is consistently found that executing a purely goal-driven saccade in the absence of a clear visual cue is more demanding, as is exhibited through slower eye movements. This finding also invites the possibility that the existence of a larger cognitive load - having to identify a cue and calculate a mirror target location to send the eyes to - enacts costs to the oculomotor system that is observed in sacrifices of saccade speed and accuracy relative to simply moving the eyes to an onscreen target. If a cognitively demanding decision does influence saccade velocities in a simple task, a natural next step is to explore how cognitive load may be reflected in saccadic properties in more challenging tasks. Fixations have been explored more often than saccades in complicated task settings and are known to vary both as a function of the task environment and of participants’ knowledge. Category learning tasks provide insight into the interplay between developing expertise in making category judgements and the corresponding trial-to-trial oculomotor activity. For instance, as knowledge of a category structure develops, participants’ fixations to task relevant cues are longer than fixations to irrelevant cues (Blair, Watson, Walshe & Maj, 2009; Chen, Meier, Blair, Watson & Wood, 2013), and there are more fixations to relevant than irrelevant cues (McColeman, Barnes, Chen, Meier, Walshe & Blair, 2014; Rehder & Hoffman, 2005), demonstrating