UBC Theses and Dissertations
Eye movements as indicators of visual and cognitive processing Fooken, Jolande
Natural tasks, such as catching a ball, involve the decision whether, when, and where to act. This dissertation examines the relationship between eye and hand movements during goal-directed manual interceptions that require rapid sensorimotor decisions. Human observers viewed and predicted the motion path of a briefly presented moving target and intercepted it at its assumed end position. Observers naturally tracked the moving target to guide interceptive hand movements. To probe the tight eye-hand link, I investigated the effect of perceptual-motor training on eye and hand movement quality (Chapter 2). Results indicate a mutual benefit of training eye and hand movements concurrently. Eye movement training alone was not sufficient to improve hand movement accuracy. However, training that required an active sensorimotor decision (eye or hand interception) enhanced eye movement quality. Next, I tested the role of eye movements during go/no-go decisions. Observers predicted whether targets passed through (go required) or missed (no-go required) a strike box. Observers' eye movements differentiated between decision outcome (go vs. no-go) on a trial-by-trial basis with an overall accuracy of 76% (Chapter 3). Moreover, I found that different eye movement phases were linked to a two-stage decision process. Whereas eye velocity during pursuit initiation corresponded to go/no-go decision accuracy, pursuit maintenance was related to successful interception timing (Chapter 4). Finally, I investigated the role of movement constraints on decision accuracy by manipulating response modality (button press vs. interceptive hand movement) and eye movements (free viewing vs. fixation; Chapter 5). Decision formation occurred earlier but less accurately when an interceptive hand movement had to be planned and executed. Eye movements (compared to fixation) enhanced decision accuracy regardless of response modality. These results indicate that perceptual decision formation occurs dynamically, relying on the continuous updating of sensory information until an action is required. In sum, this dissertation provides evidence that eye movements are directly related to neural signatures of perceptual decision making. Furthermore, eye and hand movements show interdependencies during visual predictions and manual interception. This work highlights the potential of studying eye movements as continuous readouts of ongoing sensorimotor and cognitive processes during natural tasks.
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