Decoding reward–curiosity conflict in decision-making from irrational behaviors

機械学習により「心の揺れ・葛藤」の解読に成功 --報酬と好奇心の間で揺れる想い--. 京都大学プレスリリース. 2023-05-29.Humans and animals are not always rational. They not only rationally exploit rewards but also explore an environment owing to their curiosity. However, the mechanism of such curiosity-driven irrational behavior is largely unknown. Here, we developed a decision-making model for a two-choice task based on the free energy principle, which is a theory integrating recognition and action selection. The model describes irrational behaviors depending on the curiosity level. We also proposed a machine learning method to decode temporal curiosity from behavioral data. By applying it to rat behavioral data, we found that the rat had negative curiosity, reflecting conservative selection sticking to more certain options and that the level of curiosity was upregulated by the expected future information obtained from an uncertain environment. Our decoding approach can be a fundamental tool for identifying the neural basis for reward–curiosity conflicts. Furthermore, it could be effective in diagnosing mental disorders

Bour's theorem for helicoidal surfaces with singularities

In this paper, generalizing the techniques of Bour's theorem, we prove that every generic cuspidal edge, more generally, generic $n$-type edge, which is invariant under a helicoidal motion in Euclidean $3$-space admits non-trivial isometric deformations. As a corollary, several geometric invariants, such as the limiting normal curvature, the cusp-directional torsion, the higher order cuspidal curvature and the bias, are proved to be extrinsic invariants.Comment: 21 pages, 9 figure

Introduction of Majority Vote of Neighborhood Conditions for Sneak form Reinforcement Learning

AbstractChain Form Reinforcement Learning (CFRL) was proposed for a reinforcement learning agent using low memory. In this paper, we introduce Sneak Form Reinforcement Learning (SFRL). SFRL is the method where we improve CFRL in terms of Contextual Learning. If a sequence of state-action pairs has a shortest path, a SFRL agent cuts and saves the path. To improve the performance of SFRL, we introduce Majority Vote of Neighborhood Conditions for SFRL and call this method MVNC. Majority Vote of Neighborhood Conditions is the rule which agent in an unknown state selects an action not at random but with circumjacent information. Our methods were made a comparison to Q-Learning and CFRL in several easy simulations. We examined performance and discussed the best usage environment

Angle Control of a Pneumatically Driven Musculoskeletal Model Based on Coordination of Agonist-Antagonist Muscle

In recent years, researchers have been actively pursuing research into developing robots that can be useful in many fields of industry (e.g., service, medical, and aging care). Such robots must be safe and flexible so that they can coexist with people. Pneumatic actuators are useful for achieving this goal because they are lightweight units with natural compliance. Our research focuses on joint angle control for a pneumatically driven musculoskeletal model. In such a model, we use a one-degree-of-freedom joint model and a five-fingered robot hand as test beds. These models are driven by low pressure-driven pneumatic actuators, and mimic the mechanism of the human hand and musculoskeletal structure, which has an antagonistic muscle pair for each joint. We demonstrated a biologically inspired control method using the parameters antagonistic muscle ratio and antagonistic muscle activity. The concept of the method is based on coordination of an antagonistic muscle pair using these parameters. We have investigated the validity of the proposed method both theoretically and experimentally, developed a feedback control system, and conducted joint angle control by implementing the test beds.ArticleJournal of Mechanics Engineering and Automation. 2(12):709-719 (2012)journal articl

On the Magnetostriction of Iron-Aluminium Alloys and a New Alloy "Alfer"

The magnetostriction of iron-aluminium alloys has been measured by the apparatus designed by the present investigators in various longitudinal fields of less than 1200 Oersteds. The positive magnetostriction of iron gradually increases by the addition of aluminium, while the negative one descreases. All the alloys containing more than 5.90% Al have only a positive magnetostriction, and especially in the case of alloys containing more than 8.80% Al the magnetostriction always increases with the magnetizing field or the intensity of magnetization ; showing no maximum. The magnetostriction at a constant field of 1, 100 Oersteds shows a negative value, in the range of lees than 5.3% Al content, while a positive value in the aluminium content above this percentage. In the range of the aluminium content 11.5-13.2% the magnetostriction is very high ; its highest value being 40×10 of 13.14% Al allcy. These alloys may be excellent magnetostriction materials for a supersonic cscillator and have been called "Alfer" by the present investigators

Transition Processes of \u27Freeters\u27

本稿は,日本労働研究機構が1999年に実施したフリーター97名に対するヒアリング調査データを用い,フリーター析出の契機をという観点から整理し直し,各契機ごとに重要な諸要因を抽出した.また,それぞれの契機に応じて,フリーターになった後の進路展望の変化についても検討を加えた.その結果,フリーター析出の契機は(1)選抜における非選抜,(2)移行先への不適応,(3)移行の長期化,(4)移行行動の欠如の4つに分けられ,それぞれ教育システム内部で生じた場合と,教育システムと職業システムとの間で生じた場合から成る.そしてこれらの契機において移行を阻んでいる要因としては,(1)家計要因,(2)意識要因,(3)進路指導要因,(4)教育内容要因,(5)正規労働市場要因,(6)非正規労働市場要因,(7)特殊労働市場要因が抽出された.フリーター問題は,これらの諸要因がもたらす教育から職業への移行のアポリア化の表れとして把握される.This paper examines the processes through which young people in Japan become \u27freeters,\u27using intensive interview data of 97 freeters collected by the Japan Institute of Labour in 1999. Young people become \u27freeters\u27as the result of their failures of transitionfrom an organization to another organization. The \u27organizations\u27include both educational organizations-schools and universities-and vocational organizations-companies. The main reasons of failures of transition are classified into four categories ; the failure in the entrance selection, the early desertion from the admitted organization, the prolonged selection, and the lack of transition action. The factors that foster these failures are ; the reduced household economy, the inappropriate attitudes towards jobs, the inappropriate guidance within schools, the irrelevant educational contents, the shrinking labor market for regular workers, the expanding labor market for irregular workers, the expanding labor market for peculiar types of jobs. The problem of \u27freeters\u27in Japan is redefined as the manifestation of the aporia of the transition from school to work caused by these factors

Increasing the Thermostable Sugar-1-Phosphate Nucleotidylyltransferase Activities of the Archaeal ST0452 Protein through Site Saturation Mutagenesis of the 97th Amino Acid Position

The ST0452 protein is a bifunctional protein exhibiting sugar-1-phosphate nucleotidylyltransferase (sugar-1-P NTase) and amino-sugar-1-phosphate acetyltransferase activities and was isolated from the thermophilic archaeon Sulfolobus tokodaii. Based on the previous observation that five single mutations increased ST0452 sugar-1-P NTase activity, nine double-mutant ST0452 proteins were generated with the intent of obtaining enzymes exhibiting a further increase in catalysis, but all showed less than 15% of the wild-type N-acetyl-d-glucosamine-1-phosphate uridyltransferase (GlcNAc-1-P UTase) activity. The Y97A mutant exhibited the highest activity of the single-mutant proteins, and thus site saturation mutagenesis of the 97th position (Tyr) was conducted. Six mutants showed both increased GlcNAc-1-P UTase and glucose-1-phosphate uridyltransferase activities, eight mutants showed only enhanced GlcNAc-1-P UTase activity, and six exhibited higher GlcNAc-1-P UTase activity than that of the Y97A mutant. Kinetic analyses of three typical mutants indicated that the increase in sugar-1-P NTase activity was mainly due to an increase in the apparent k(cat) value. We hypothesized that changing the 97th position (Tyr) to a smaller amino acid with similar electronic properties would increase activity, and thus the Tyr at the corresponding 103rd position of the Escherichia coli GlmU (EcGlmU) enzyme was replaced with the same residues. The Y103N mutant EcGlmU showed increased GlcNAc-1-P UTase activity, revealing that the Tyr at the 97th position of the ST0452 protein (103rd position in EcGlmU) plays an important role in catalysis. The present results provide useful information regarding how to improve the activity of natural enzymes and how to generate powerful enzymes for the industrial production of sugar nucleotides. IMPORTANCE It is typically difficult to increase enzymatic activity by introducing substitutions into a natural enzyme. However, it was previously found that the ST0452 protein, a thermostable enzyme from the thermophilic archaeon Sulfolobus tokodaii, exhibited increased activity following single amino acid substitutions of Ala. In this study, ST0452 proteins exhibiting a further increase in activity were created using a site saturation mutagenesis strategy at the 97th position. Kinetic analyses showed that the increased activities of the mutant proteins were principally due to increased apparent k(cat) values. These mutant proteins might suggest clues regarding the mechanism underlying the reaction process and provide very important information for the design of synthetic improved enzymes, and they can be used as powerful biocatalysts for the production of sugar nucleotide molecules. Moreover, this work generated useful proteins for three-dimensional structural analysis clarifying the processes underlying the regulation and mechanism of enzymatic activity

Interest in Infectious Diseases specialty among Japanese medical students amidst the COVID-19 pandemic: A web-based, cross-sectional study

IntroductionThe emergence of the novel coronavirus disease of 2019 (COVID-19) has led to huge disruptions in the medical field and society. The significance of training and education for experts has been increasingly acknowledged in Japan, where the number of infectious disease (ID) specialists is reportedly insufficient. In this paper, we report the results of a web-based survey that was conducted to reveal the ways in which the COVID-19 pandemic has influenced medical students' awareness of ID specialists and future career choices. MethodThis cross-sectional descriptive study was conducted in March 2021 and targeted 717 medical students belonging to Medical School of Okayama University, Japan. The questionnaire consisted of four questions meant to assess students' knowledge and future intentions of becoming ID specialists. ResultsWe obtained 328 eligible questionnaires (response rate: 45.7%). Of 227 (69.2%) students who were aware of ID specialists, 99 (43.6%) answered that they came to know about them only after the pandemic, 12 (3.7%) answered that their interest in being an ID specialist arose during the pandemic, while 36 (11.0%) responded that they would rather not become ID specialists. At the time of the survey, 5 students (1.5%) were aiming to become ID specialists. ConclusionWe observed a very low rate of interest to be an ID specialist among medical students. The experience of the pandemic does not seem to have influenced Japanese medical students to choose ID as a specialty for their careers. Continuous efforts to increase the number of ID specialists are necessary in Japan as a countermeasure against the coming pandemic