We explore the use of machine learning to detect under-rotation in figure skating jumps. Under- rotation in jumps is difficult for the skater to sense but learning to recognize under-rotation is an impor- tant part of learning proper jump technique. To address this difficulty, we present the Under-rotation Monitor, or UR Monitor, a system for detecting under-rotated figure skating jumps in real-time. UR Monitor uses a single inertial measurement unit (IMU) attached to the skater's waist that sends a stream of accelerometer and gyroscope data to a mobile phone via Bluetooth. The mobile phone creates and sends an input vector of each jump to a web-hosted API that returns a response from our trained classifier indicating whether it considered that jump as 'under-rotated', or 'completed rotation'. The classifier is trained and tested on a collection of 444 jumps, of which only 121 are under-rotated. We also present a process for addressing an imbalanced dataset on which the classifier trains. Our classifier achieves an F1-score of only 0.66, suggesting that noise and imbalance in the data set are significant issues.

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Little is known about how healthy aging impacts figure-ground (FG) perception, which is critical in organizing complex visual input into coherent figures. Inhibitory-suppression is thought to be critical in resolution between competing FG interpretations. Given the age-related changes to inhibitory cortical mechanisms, my thesis investigated the hypothesis that processes underlying FG organization are impaired in aging. We explored the effects of age on the convexity context effect (CCE): the tendency to perceive convex regions as figural [i.e., P(Convex=Figure)] increases with surrounding convex and concave regions. In Chapter 2, we observed that adding context by increasing region number, increased P(Convex=Figure) in younger and older observers, but this CCE was significantly reduced in older adults. Reducing competition between perceptual interpretations by heterogeneously colouring convex regions, thereby invalidating the alternative {Concave=Figure} stimulus interpretation, greatly increased P(Convex=Figure) in older observers. These results supported the notion that aging impairs FG organization, particularly in relatively high competition contexts. In Chapter 3, we explored the possibility that reduced presumption of depth in our stimuli might explain the reduced the CCE in older observers by adding texture motion to region fills consistent with depth in the stimulus. The results were inconsistent with the hypothesis, but supported the reduced inhibitory-suppression hypothesis of the age effect. In Chapter 4, we explored the neural activation associated with the processing mechanisms underlying the resolution of FG competition. The results indicated that the N250 in younger observers but not older observers is sensitive to high vs. low competition contexts. Furthermore, individual differences in this N250-competition effect were correlated with the behavioural effect of competition. Our findings are consistent with the hypothesis that the processing underlying FG organization is impaired in senescence, which may stem from reduced efficacy of the neural architecture supporting this ability. Various implications of this work are discussed. / Dissertation / Doctor of Philosophy (PhD)

京都大学 / 新制・課程博士 / 博士(文学) / 甲第24339号 / 文博第913号 / 新制||文||729(附属図書館) / 京都大学大学院文学研究科文献文化学専攻 / (主査)教授 VASUDEVA Somdev, 教授 横地 優子, 教授 宮崎 泉 / 学位規則第4条第1項該当 / Doctor of Letters / Kyoto University / DFAM

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Learning relational terms such as verbs and prepositions is fundamental to language development. To learn relational words, children must first dissect and process dynamic event components, and then uncover how the particular language they are learning encodes these constructs. Building on a new area of research, this dissertation investigated two event components, figure (i.e., the moving entity) and ground (i.e., the stationary setting) that are central to learning relational words. In particular, we examine how English- and Japanese-reared infants process figures and grounds in nonlinguistic events and how language learning interacts with their conceptualization of these constructs. Four studies were designed to probe our questions. Study 1 examined English-reared infants' ability to form nonnative ground categories encoded only in Japanese. For example, "crossing a road," which extends in a line and is bounded, is expressed differently than "crossing a field" that extends in a plane and is unbounded. We found that infants can detect the geometry of the ground and form a nonnative ground category. Study 2 indicated that the path of an action plays a role in construing these categorical ground distinctions such that without the bounded paths infants do not differentiate between grounds. Study 3 demonstrated that even though infants notice figures and grounds in static representations of the dynamic events (even earlier for the ground discrimination), the Japanese categorical ground differentiation no longer emerged. In the last set of studies, we showed that despite the sensitivity to the event structure and categorical ground distinctions in dynamic events by both English- and Japanese-reared infants (Study 4a), only Japanese toddlers retained these categorical distinctions (Study 4b). Overall, these results suggest that 1) infants distinguish between figures and grounds in events with differential attention to static and dynamic displays; 2) before learning much about their native language infants form nonnative event categories; and 3) the process of learning language appears to shift earlier formed categorical boundaries. / Psychology