One Good Turn Deserves Another: Constraint Hierarchies for Action Selection in Bimanual Rotation
Open Access
- Author:
- Chapman, Kate M
- Graduate Program:
- Psychology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 20, 2013
- Committee Members:
- David A. Rosenbaum, Dissertation Advisor/Co-Advisor
Judith Fran Kroll, Committee Member
Bradley Paul Wyble, Committee Member
Carol Anne Miller, Committee Member - Keywords:
- action selection
object manipulation
end-state comfort
bimanual rotation
bimanual action
motor planning - Abstract:
- The primary aim of this thesis was to understand action selection in object manipulation. The four experiments presented in this thesis were designed to address the degrees of freedom problem by seeking to identify the constraints that are brought to bear in object manipulation tasks. I investigated constraints at the cognitive level of the action selection system, specifically considering constraints related to the goals and intentions of the actor. In addition to identifying the relevant constraints in object manipulation, I also sought to determine whether the relative priority of the identified constraints was consistent, or instead shifted based on the demands of each task. I conducted a series of bimanual rotation experiments to address these questions. In Experiment 1, I found that participants tended to complete rotations that allowed them to end with comfortable postures on the handles. This tendency to end comfortably was more important than the tendency to start the rotation in a comfortable posture or the preference to pronate in rotation. I also found that it was more important for participants to pronate in rotation than to start the rotation in comfortable postures. Experiment 1’s results also revealed that participants rotated the disks in symmetry on the majority of trials, both for sequential rotation and simultaneous rotation. This suggested that ending comfortably and rotating symmetrically were both very important constraints in action selection for this task. Experiments 2 and 3 were designed to determine the relative priority of two important constraints: the preference to end in a comfortable posture and the preference to rotate in symmetry. The results of Experiments 2 and 3 revealed that both constraints were very important in bimanual rotation. I found that when it was possible to satisfy both constraints without incurring a high cost (in the form of adopting an extreme initial grasping posture), participants selected actions that allowed them to both end comfortably and rotate symmetrically. However, on trials in which satisfying both constraints concurrently did incur a high cost (extreme grasping postures), participants tended to satisfy one of the two constraints, but not both. Whether they prioritized ending comfortably or moving symmetrically critically depended on whether they rotated their hands simultaneously or sequentially. Overall, the results of Experiments 2 and 3 demonstrated that both end-state comfort and symmetry were very important constraints in action selection for bimanual rotation. In addition, the action selection system was critically flexible and sensitive to the demands of the task on a trial-by-trial basis. The final experiment extended the results of Experiments 2 and 3 by investigating the role of extreme postural rotation in the perceived comfort of a bimanual posture. The results of Experiment 4 demonstrated that bimanual postures including at least one extreme grasp were much less comfortable than other postures without extreme rotation. In addition, I found that the less comfortable grasp in the pair of postures had a much larger influence on the overall comfort rating than the more comfortable grasp. These findings provide support for my interpretation of Experiment 2 and 3’s results. Overall, participants preferred to both end comfortably and rotate symmetrically, but were not willing to satisfy both constraints if it required an extreme rotation of one or more hands. Participants aimed to concurrently satisfy multiple important constraints with each action but evaluated the cost of each strategy for each task. Thus, this study of bimanual object manipulation has revealed a sensitive and flexible action selection system.