Gaze strategies in perception and action
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When you want to pick up an object, it is usually a simple matter to reach out to its location, and accurately pick it up. Almost every action in such a sequence is guided and checked by vision, with eye movements usually preceding motor actions (Hayhoe & Ballard, 2005; Hayhoe, Shrivastava, Mruczek, & Pelz, 2003). However, most research in this area has been concerned about the sequence of movements in complex “everyday” tasks like making tea or tool use. Less emphasis has been placed on the object itself and where on it the eye and hand movements land, and how gaze behaviour is different when generating a perceptual response to that same object. For those studies that have, very basic geometric shapes have been used such as rectangles, crosses and triangles. In everyday life, however, there are a range of problems that must be computed that go beyond such simple objects. Objects typically have complex contours, different textures or surface properties, and variations in their centre of mass. Accordingly, the primary goals in conducting this research were three fold: (1) To provide a deeper understanding of the function of gaze in perception and action when interacting with simple and complex objects (Experiments 1a, 1b, 1c); (2) To examine how gaze and grasp behaviours are influenced when you dissociate important features of an object such as the COM and the horizontal centre of the block (Experiments 2a, 2c); and (3) To explore whether perceptual biases will influence grasp and gaze behaviours (Experiment 2b). The results from the current series of studies showed the influence of action (i.e., the potential to act) on perception in terms of where we look on an object, and vice versa, the influence of perceptual biases on action output (i.e. grasp locations). In addition, grasp locations were found to be less sensitive to COM changes than previously suggested (for example see Kleinholdermann, Brenner, Franz, & Smeets, 2007), whereas fixation locations were drawn towards the ‘visual’ COM of objects, as shown in other perceptual studies (for example see He & Kowler, 1991; Kowler & Blaser, 1995; McGowan, Kowler, Sharma, & Chubb, 1998; Melcher & Kowler, 1999; Vishwanath & Kowler, 2003, 2004; Vishwanath, Kowler, & Feldman, 2000), even when a motor response was required. The implications of these results in terms of vision for Perception and vision for Action are discussed.