Doctor of Philosophy (PhD)



Document Type



The focus of this dissertation was to explore the effects of potential vertical-horizontal (V-H) illusory influences on perceptuomotor control. As part of this focus, we examined the potential use of separate cortical visual streams: the ventral visual stream for perception and the dorsal visual stream for action. Three studies were conducted to determine the effects of the V-H illusion influences on length estimations using upper limb point-to-point movements and lower limb stepping movements, involving various illusory configurations, movement directions, gaze directions. After a short introduction (Chapter 1) and a more detailed review of existing literature (Chapter 2), we present manuscripts on three studies. In the first study, we determined that manual length estimations of perpendicular segment lengths using curved point-to-point reaches corresponded to V-H illusory influences for movements, which began on the V-H illusion configurations rather than away from the illusion center. We concluded that encouraging gaze fixation on the center of the configuration likely contributed to the greater illusory influences over sensorimotor control. In the second study (Chapter 4), we directly assessed whether restricting gaze on the configuration or movement would alter V-H illusory influences on manual length estimations. Results revealed that restricting gaze on the configuration or movement space did alter general V-H illusory influences over sensorimotor control. We determine that the exploitation of V-H illusory cues can guide of upper limb movements given the specific gaze parameters. In Chapter 5 we assessed whether restricting gaze to the configuration or movement space also maintained V-H illusory effects on length estimations using stepping movements. Results demonstrated illusory influences, which did not exist for length estimations using movements of the lower limb with different gaze restrictions, did exist for movement planning and early movement execution. We concluded that the exploitation of vertically presented V-H illusory cues cannot guide the completion of lower limb horizontal plane movements, even given specific gaze parameters. Taken together, these data provide evidence to support that given the right circumstances exploitation of simple deceptive cues can influence relative aspects of perceptuomotor control; however, people can utilize the separate pathways involving visual control for perception and action to produce manual length estimations which differ from perception.



Committee Chair

Hondzinski, Jan