No description available.

Dual-task studies have shown higher sensitivity for stimuli presented at the targets of upcoming actions. Generally, movement outcome feedback is also obtained at action targets. This thesis examined whether attention is directed to action targets for the purpose of action selection, as previously concluded, or if attention is directed to monitor feedback about movement outcomes as supported by skilled-action research. Across seven experiments, participants executed either a pointing movement (Experiments 1 – 5) or a saccade (Experiments 6 and 7), while simultaneously identifying a discrimination target ('E' or '3') among distractors (2s and 5s). Action targets were generally cued by a central arrow. Discrimination target identification accuracy measured attention allocation. Crucially, movement accuracy feedback was presented at a spatially separate location from the action target. It was found that during the planning of goal-directed actions, attention is allocated to monitor movement outcomes, even if this information is provided at a spatially separate location from the action target. Attending the separate feedback location resulted in slower reaction times and less accurate pointing. Clear and consistent perceptual enhancement was also demonstrated at the action target location, even when no intrinsic or extrinsic feedback about the action could have been gained from attending there. Specific to saccades, it was found that attention is allocated before saccade execution to both the saccade goal and to the predicted future retinal location of feedback information. Lastly, perceptual performance is greater in general when participants perform the dual-task visually open-loop, that is without visual feedback from the moving hand. These results are novel in showing that attention appears to be required for action target selection, independently of the need to monitor expected locations of feedback.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

In the influential perception-action model, the ventral visual system of the primate brain serves to obtain knowledge of objects in the environment, while the dorsal system serves to control actions in interaction with those objects. In recent years, criticism of the model has gained momentum following reports of evidence that involvement of the two systems may not principally depend on whether observers are engaged in action or perception tasks. This thesis appraises the perception-action model over the course of five experiments that test a number of the model’s central assertions. Evidence for an alternative functional characterization of the dorsal and ventral systems is obtained. Specifically, the evidence suggests that the dorsal system can be involved in both action and perception on the basis of fast egocentric information pickup, while the ventral system can be involved in both perception and action on the basis of slower allocentric information pickup. This raises the possibility that a more fundamental distinction pertains to the characteristics of information pickup by the two systems rather than to the behavioral functions subserved. The thesis develops a stance in which involvement of the two systems in the visual guidance of behavior is dependent on their operational characteristics in combination with the constraints of the task. The proposed relevant task constraints are: (i) whether tasks allow for egocentric and/or allocentric information pickup, (ii) the amount of time that is available for information pickup in a task and, possibly, (iii) whether stimuli are located within or outside functional space (the space that affords action for an observer). Whether a task requires an immediate or a delayed response is of less importance. It is argued that while the typical requirements of perception and action tasks bring about a tight coupling between perception and the ventral system and action and the dorsal system, this coupling is not invariant; perception can involve fast egocentric information pickup and action can involve slower allocentric information pickup. The findings are discussed in the context of higher-level theories of visual perception. It is proposed that the view of the dorsal and ventral visual systems that is suggested by the findings presented in this thesis corresponds better with ecological than with constructivist approaches to visual perception. / published_or_final_version / Human Performance / Doctoral / Doctor of Philosophy

No description available.

No description available.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 76-82).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 82-85).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 75-82).

An experiment was designed to test the role of knowledge of results (KR) in perceptual trace (PT) development with KR temporal delay intervals and presence or absence of KR as independent variables. Each of three groups of 10 Ss_ per group had a specific arrangement of KR temporal delay intervals such that over all groups there were two KR delay intervals of 1.0 and 30.0 seconds, two post-KR delay intervals of 10.0 and 39.0 seconds and two intertrial intervals (ITI) of 11.0 and 40.0 seconds. All groups performed a linear positioning task over three phases of responding in order to vary the presence or absence of KR. Two hypotheses were tested. Hypothesis 1, which stated that the post-KR delay interval is the locus of post-KR phase response bias, was not supported by the results. However, there was a tentative finding that the KR phase ITI is the locus of post-KR phase response bias, which supports both the concept of a functioning,PT and the concept that the PT is formed solely from response-produced feedback (FB). Hypothesis 2, which stated that KR does not permanently affect response variability, was supported by the results. Response variability was the same prior to (i.e., pre-KR phase) and following (i.e., post-KR phase) the presentation of KR. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate