Abstract
The ability of an agent to accomplish a trajectory during a certain motor task depends on the fit between external (environment) and internal (agent) constraints, also known as affordance. A model of difficulty for a generalized reaching motor task is proposed as an affordance-related measure, as perceived by a specific agent for a given environment and task. By extending the information-based Index of Difficulty of a trajectory, a stochastic model of difficulty is formulated based on the observed variability of spatial trajectories executed by a given agent during a repetitive motor task. The model is tested on an experimental walking dataset available in the literature, where the repetitive stride movement of differently aged subjects (14 “old” subjects aged 50–73; 20 “young” subjects aged 21–37) at multiple speed conditions (comfortable, ~30% faster, ~30% slower) is analyzed. Reduced trajectory variability in older as compared to younger adults results in a higher Index of Difficulty (slower: +24%, p < 0.0125; faster: +38%, p < 0.002) which is interpreted in this context as reduced affordance. The model overcomes the limits of existing difficulty measures by capturing the stochastic dependency of task difficulty on a subject’s age and average speed. This model provides a benchmarking tool for motor performance in biomechanics and ergonomics applications.
Highlights
Studies on human or robot motor performance pertain to an interdisciplinary field of research with several applications ranging from robotics to biomechanics to ergonomics.This performance is typically measured in human or robot agents by analyzing a trajectory executed during a motor task
This study deals with affordance measures of observed reaching motor tasks executed by subjects
The issue is of great scientific and industrial interest as it pertains the ability of a human agent with given dynamic features to accomplish different trajectories constrained by the environment and by internal constraints
Summary
Studies on human or robot motor performance pertain to an interdisciplinary field of research with several applications ranging from robotics to biomechanics to ergonomics. The various formulations of the ID [15,17,18], and field studies [19,20,21,22,23,24] refer to simple “point-to-point” reaching motor tasks without considering the travelled path In such experiences, subjects can fail in meeting the final target and accuracy issues are addressed. The model quantifies the Index of Difficulty as a probabilistic affordancerelated measure of a generalized reaching task, based on the observed variability of the repeated trajectories executed by a given agent.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
