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Title: The kinematics of human tool use
Author: Dickson, Ruth
ISNI:       0000 0004 7432 215X
Awarding Body: Bangor University
Current Institution: Bangor University
Date of Award: 2018
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The aim of this thesis was to use kinematic analysis to further our understanding of tool Use. We wanted to investigate whether there were similarities in how people picked up objects with their hand and with a tool, and whether these remained when we manipulated the ratio and motor equivalence of the tool. This allowed us to investigate the concepts of end-effector control and internal tool models. Participants compensated for the ratio of the red 1.4:1 tool to the same extent when only cued with tool colour as when having all of the information. This shows that information about the tool must have been stored in memory, supporting the idea of internal tool models. Participants produced qualitatively similar movements with our tools and the hand, showing no difference in the peak velocity and altering peak end-effector aperture based on tool ratio. Further to this, participants displayed similar adaptive mechanisms in response to visual uncertainty with the hand, the blue 1:1 tool and the red tool, but not with the yellow 0.7:1 tool however. Throughout the thesis participants also compensated less for the ratio of this tool than the red one. Whilst attempting to investigate the imperfect compensation seen with both tools we understood this issue more. Participants overestimated object size with the yellow tool and performed more poorly at a size discrimination task as well. This pointed towards a biased internal tool model, tending towards the aperture of the hand. This accounted for the asymmetric compensation seen between the red and yellow tools. We concluded that the imperfect compensation for tool ratio was caused by noise in the internal tool models and that the yellow tool model was then biased as well, further reducing compensation. Our findings support the idea that the precision with which we can use a tool could be modulated by prior experience with that transformation. We also believe that the degree of motor equivalence of the tool contributes to precision of use, with tools that are not directly equivalent taking longer to develop a robust internal model for. However, even tools without direct motor equivalence display some of the hallmarks of reaching and grasping with the hand, suggesting that grasping movements could be encoded in end-effector units.
Supervisor: Watt, Simon Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available