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- Creators: Artemiadis, Panagiotis
Description
Object manipulation is a common sensorimotor task that humans perform to interact with the physical world. The first aim of this dissertation was to characterize and identify the role of feedback and feedforward mechanisms for force control in object manipulation by introducing a new feature based on force trajectories to quantify the interaction between feedback- and feedforward control. This feature was applied on two grasp contexts: grasping the object at either (1) predetermined or (2) self-selected grasp locations (“constrained” and “unconstrained”, respectively), where unconstrained grasping is thought to involve feedback-driven force corrections to a greater extent than constrained grasping. This proposition was confirmed by force feature analysis. The second aim of this dissertation was to quantify whether force control mechanisms differ between dominant and non-dominant hands. The force feature analysis demonstrated that manipulation by the dominant hand relies on feedforward control more than the non-dominant hand. The third aim was to quantify coordination mechanisms underlying physical interaction by dyads in object manipulation. The results revealed that only individuals with worse solo performance benefit from interpersonal coordination through physical couplings, whereas the better individuals do not. This work showed that naturally emerging leader-follower roles, whereby the leader in dyadic manipulation exhibits significant greater force changes than the follower. Furthermore, brain activity measured through electroencephalography (EEG) could discriminate leader and follower roles as indicated power modulation in the alpha frequency band over centro-parietal areas. Lastly, this dissertation suggested that the relation between force and motion (arm impedance) could be an important means for communicating intended movement direction between biological agents.
ContributorsMojtahedi, Keivan (Author) / Santello, Marco (Thesis advisor) / Greger, Bradley (Committee member) / Artemiadis, Panagiotis (Committee member) / Helms Tillery, Stephen (Committee member) / Buneo, Christopher (Committee member) / Arizona State University (Publisher)
Created2017
Description
Social discounting underlies individual altruistic decision-making, and it is frequently measured as the amount of hypothetical money one is willing to forgo for another person as a function of social distance. In the classic social discounting task, individual participants are asked to imagine their friends along a continuum of social distance, that is then used to estimate participant’s social discounting rate. While an ever-growing proportion of social interactions takes place over social media, no research has yet characterized social discounting in that context. Moreover, no research has estimated social discounting rate using real persons’ social distance, instead of the hypothetical continuum described above. Using existing social media indicators of social distance, it is now possible to estimate social discounting rate based on real people, which may lead to more accurate social discounting measurements and may expand the discounting model to real-life situations. Specifically, using computer algorithms to estimate the social distance from social media data makes it possible to assess the utility of numeric social distance indicators and the most appropriate ways to represent them. The proposed study examined the extent to which a hyperbolic model for social discounting fits social distance information retrieved from Facebook pages; and assessed whether there were differences in discounting rate when real or hypothetical social distance is used; also to further investigate whether discounting rates based on real persons are in fact based on perceived social distance by the participant, or on the imaginary social distance scale (i.e., an experimental artifact.)
It was found that the social discounting model can be applied in the social media context, even when real Facebook friends’ profiles were used as substitutes of numeric social distance indicators. Additionally, people showed similar altruistic tendencies in both the numeric and profile social discounting tests on the Facebook environment. These findings were qualified, however, by a high rate of nonsystematic data for the profile group; a rate much higher than traditional numeric paradigm. This discrepancy suggested that the allocation rates between numeric and profile approaches need further investigation to determine the factors affecting individuals’ generosity as a function of social distance indicators.
It was found that the social discounting model can be applied in the social media context, even when real Facebook friends’ profiles were used as substitutes of numeric social distance indicators. Additionally, people showed similar altruistic tendencies in both the numeric and profile social discounting tests on the Facebook environment. These findings were qualified, however, by a high rate of nonsystematic data for the profile group; a rate much higher than traditional numeric paradigm. This discrepancy suggested that the allocation rates between numeric and profile approaches need further investigation to determine the factors affecting individuals’ generosity as a function of social distance indicators.
ContributorsJiang, Linle (Author) / Miller, Paul A. (Thesis advisor) / Robles-Sotelo, Elias (Committee member) / Silva, Yasin N. (Committee member) / Arizona State University (Publisher)
Created2018