Asymmetric Missing-data Problems: Overcoming the Lack of Negative Data in Preference Ranking

In certain classification problems there is a strong a asymmetry between the number of labeled examples available for each of the classes involved. In an extreme case, there may be a complete lack of labeled data for one of the classes while, at the same time, there are adequate labeled examples for the others, accompanied by a large body of unlabeled data. Since most classification algorithms require some information about all classes involved, label estimation for the un-represented class is desired. An important representative of this group of problems is that of user interest/preference modeling where there may be a large number of examples of what the user likes with essentially no counterexamples.Recently, there has been much interest in applying the EM algorithm to incomplete data problems in the area of text retrieval and categorization. We adapt this approach to the asymmetric case of modeling user interests in news articles, where only labeled positive training data are available, with access to a large corpus of unlabeled documents. User modeling is here equivalent to that of user-specific document ranking. EM is used in conjunction with the Naive Bayes model while its output is also utilized by a Support Vector Machine and Rocchio's technique.Our findings demonstrate that the EM algorithm can be quite effective in modeling the negative class under a number of different initialization schemes. Although primarily just the negative training examples are needed, a natural question is whether using all of the estimated labels (i.e., positive and negative) would be more (or less) beneficial. This is important considering that, in this context, the initialization of the negative class for EM is likely not to be very accurate. Experimental results suggest that EM output should be limited to negative label estimates only.     

Over-education and its opportunity cost in Japan

In this paper, we investigate the determinants of over-education in Japan and evaluate its opportunity costs for university graduates. To this end, we use the REFLEX data. Results reveal that over-education level in Japan is high and it brings an important wage penalty for Japanese workers. Large firm and high occupations point toward a significant reduction in the likelihood of over-education. Results for wage regressions for over-education indicate that Japanese workers who achieve jobs in large organizations will experience 20 % increase in their wage due to the firm size and, if over-educated, their increase in wage will remain positive. Results for women are puzzling as there is no significant effect associated with gender.     

Teachers’ reflection on PISA items and why they are so hard for students in Serbia

The study explores how teachers perceive and go about students’ thinking in connection to particular mathematical content and how they frame the notion of applied mathematics in their own classrooms. Teachers’ narratives are built around two released PISA 2012 mathematics items, the ‘Drip rate’ and ‘Climbing Mount Fuji’ (will be referred to as the Fuji item). Teachers show concordance as to the reasons that could make either of the items difficult for students and are able to provide more examples justifying their reasoning for the ‘Fuji’ item. Suggestions linked to making the items more familiar to the students mostly relate to de-contextualization of the items’ content towards a more formal mathematical record. The teachers agree that students need only basic mathematical knowledge, at a level learned during elementary school, in order to solve these problems. Yet, at the same time, many teachers have difficulty clearly verbalising which procedures students are expected to follow to be able to solve the tasks. Disagreement among the teachers is noticeable when labelling the most difficult part(s) of each of the selected items. Mathematics teachers show openness for learning on how to create math problems we examined in this study, but question the purpose and meaning in incorporating more such problems in their own teaching.     

Why do tertiary education graduates regret their study program? A comparison between Spain and the Netherlands

In this paper we investigate the determinants of regret of study program for tertiary education graduates in Spain and the Netherlands. These two countries differ in their educational system in terms of the tracking structure in their secondary education and the strength of their education-labor market linkages in tertiary education. Therefore, by comparing Spain and the Netherlands, we aim at learning about the consequences that the two educational systems might have on the regret of study program in tertiary education. Basing on the psychological literature on regret, we derive some expectations on the determinants of regret of study program. Results reveal that both, education track and education-labor mismatch of tertiary education, are important determinants of the likelihood of program regret. Results allow us to derive some policy recommendations on the tertiary education system.     

“Is there an equal (amount of) juice?” Exploring the repeated question effect in conservation through conversation

The aim of this paper is to highlight and discuss advantages and constraints of different methods applied within the field of children's thinking studies, through the test of the repeated question hypothesis validity, using the conservation of liquid task. In our perspective, the Piagetian interview is an ecologically valid context for externalization and modification of children's thinking. We used an experimental procedure organized in standard and modified tasks, involving primary school children in Serbia. The results of quantitative and qualitative analyses show that the repeated question is not the unique cause of children's misleading in demonstrating to understand conservation. Other dimensions explain why children change their answers when they are tested by the two tasks we used, which offers an insight into the influence of research procedures on children's answers.     

Experimental micro-histories,private speech and a study of children’s learning and cognitive development / Microhistorias experimentales,habla privada y un estudio del aprendizaje y el desarrollo cognitivo en los niños

Abstract

In this paper, we present the recent development of a methodological approach originally devised by Perret-Clermont and Schubauer-Leoni called ‘experimental micro-histories’. This approach allows us to investigate processes of change that often seem to be underestimated in the typical experiments used in developmental psychology that focus on the average impact of certain factors. Two dyads were studied in-depth to understand how, for better or for worse, children use elements learned from previous conversations in their subsequent self-regulatory processes. Different trajectories of private-social speech were studied through different phases (child-adult scaffolding phase and a subsequent child-child interaction phase) and will be discussed in order to reconsider the necessity of adopting a micro-historical focus on developmental processes of change.