Perception-action coupling in interceptive tasks
Open Access
- Author:
- Rothenberg-Cunningham, Alek
- Graduate Program:
- Kinesiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 08, 2014
- Committee Members:
- Karl Maxim Newell, Dissertation Advisor/Co-Advisor
Karl Maxim Newell, Committee Chair/Co-Chair
John Henry Challis, Committee Member
Robert Scott Kretchmar, Committee Member
Rick Owen Gilmore, Committee Member - Keywords:
- Perception
Interception
time-to-contact
time-to-peak velocity - Abstract:
- A central issue for the theory of perception-action coupling is the identification and characterization of information that constrains and influences the emerging movement behavior exhibited by humans and other animals. We addressed the question of what information at the levels of the environment and the performer is coupled in interceptive actions and how this coupling is influenced by manipulations to the environmental and task objectives. We examined the temporal coordination of interceptive striking actions by measuring the kinematic information of time-to-peak velocity (TPV) relative to the environmental information of time-to-contact (TTC) that were unified in a dimensionless variable in the form of the ratio of TTC:TPV that could indicate underlying movement strategies for accomplishing given task objectives. In Experiment 1 the TTC:TPV ratio indicated that a similar strategy of making contact while the effector is positively accelerating was used by younger and older children, adolescents, and adults for the task of striking a target for maximal distance. The evidence showed that the strength of the coupling between TPV and TTC increased with age and that for all age groups the TTC:TPV ratio varied only slightly in comparison to the magnitude of change in the independent kinematic variable of target velocity. It was also revealed that the structure of the TTC:TPV ratio was different for hits and touches (i.e. foul balls), with hits characterized by lower overall values of both TTC and TPV, and a closer temporal mapping of TPV with TTC for hits compared to touches. These findings are evidence that the TTC:TPV ratio is consistent with the concept of an invariant characteristic. In Experiment 2 we found evidence that the TTC:TPV ratio was influenced differentially by the spatiotemporal constraints imposed by target velocity and distance criteria. However, the magnitude of change in the independent variables was much greater compared to the amount of change in the TTC:TPV ratio that was shown to decrease with increasing target velocity and increase as distance criteria required that the target be struck farther. This is evidence that further supports the TTC:TPV ratio as an invariant characteristic that facilitates stable performance in striking targets with sub-maximal effector velocity at TTC and is consistent with the concept of non-linearity in the relationship between the changing environmental information and the action relevant information. In Experiment 3 we manipulated the velocity of the target and the duration of time that the target was visible from the outset of target motion for the task of striking the target for maximal distance. The results showed that the maximal distance and dispersion of the distance scores decreased as visual occlusion time increased, and to a greater degree for slower moving compared to faster moving targets. This is evidence that is consistent with the theory of direct perception that assumes that action is coordinated in concert with the availability of the perceptual information most relevant to the task. A confounding effect of target vision time and distance of target trajectory was revealed in a strategy whereby participants initiated movement earlier, presumably in order to close the distance between the effector and target before occlusion onset. The TTC:TPV ratio indicated that targets were struck later after peak effector velocity with increasing visual occlusion, with larger overall values of the ratio at the lower target velocity. Again, the difference of change in the TTC:TPV ratio was non-linear with respect to the magnitude of change in the independent variables. These results show that the TTC:TPV ratio does capture and describe the adaptations in striking movements that occur as a result of the influence of task and environmental constraints. Overall, the experiments showed that environmental information supports the coordination of perception in action and that the temporal organization of the striking action was influenced by changes in the task and environmental constraints. The increasing strength of the coupling of TTC and TPV with age implicates the TTC:TPV ratio as an affordance for action in that it furnishes the performer a functional temporal structure for coordinating peak effector velocity relative to TTC. Finally, the non-linear shift in the TTC:TPV ratio relative to the degree of change in the kinematic independent variables in all tasks implicates a facilitating role of the TTC:TPV ratio in stabilizing interceptive performance, consistent with the concept of an attractor, for these striking tasks. The findings support the proposition that TTC:TPV ratio is an organizational variable for temporal coordination of movement kinematics relative to environmental information. The unified, dimensionless value of the TTC:TPV ratio has implications for perception-action coupling research that seeks, in part, to characterize movement coordination in terms of a variable that reflects a “compression” of information (Turvey, 1990) that is geared towards achieving a movement solution despite an abundance of information. Consistent with a dynamical systems approach to the organization and coordination action, the TTC:TPV ratio is shown as a variable that represents a stable, self-organized movement pattern that can adapt to meet different demands imposed by changing constraints. The TTC:TPV ratio also highlights the dependence of the performer on the availability of environmental information for coordinating movement kinematics, as outlined by James Gibson’s (1979) theory of direct perception. Further work could include developing a spatial ratio counterpart to the TTC:TPV ratio and a unification of both spatial and temporal facets in a dimensionless variable that characterizes spatiotemporal movement organization for interceptive striking tasks. The implications from such a development can impact several facets of skill development and coordination that include both perceptual and action processes.