The Sierpinski Object in the Scott Realizability Topos

We study the Sierpinski object $\Sigma$ in the realizability topos based on Scott's graph model of the $\lambda$-calculus. Our starting observation is that the object of realizers in this topos is the exponential $\Sigma ^N$, where $N$ is the natural numbers object. We define order-discrete objects by orthogonality to $\Sigma$. We show that the order-discrete objects form a reflective subcategory of the topos, and that many fundamental objects in higher-type arithmetic are order-discrete. Building on work by Lietz, we give some new results regarding the internal logic of the topos. Then we consider $\Sigma$ as a dominance; we explicitly construct the lift functor and characterize $\Sigma$-subobjects. Contrary to our expectations the dominance $\Sigma$ is not closed under unions. In the last section we build a model for homotopy theory, where the order-discrete objects are exactly those objects which only have constant paths

Accounting for economic growth in the Netherlands since 1913

This paper applies a growth accounting approach to monitor growth performance of the Netherlands since 1913, which looks at the contribution of, labour, human capital, physical and knowledge capital to real output growth. The paper also compares growth and level of per capita income and productivity in the Netherlands with that of other Northwest European countries. The paper includes an extensive appendix with annual figures from 1913 to 1994.

Culture Matters: French-German Conflicts on European Central Bank Independence

With the Maastricht treaty, the members of the Eurozone agreed on the establishment of a very independent European Central Bank, as well as making their National Central Banks far more independent. However, over the years French political leaders systematically brought forward proposals undermining the ECB's independence, to the dismay of Germany. A pattern that surfaced again during the current sovereign debt crisis and has complicated finding a timely and unified answer to the problems. The article conducts tests of various factors expected to influence the preference for central bank independence. It shows that economic explanations are unable to account for the persistent differences amongst European member-states on this issue. Instead, cultural differences in attitudes, especially a nation's score on the dimension of Power Distance - its acceptance of centralisation of power in a small set of political leaders or institutions - does show a correlation with the different levels of internalisation of the Central Bank independence norm.Central Bank Independence; Culture; European Central Bank; Franco- German relations

Fluency in dialogue: Turn‐taking behavior shapes perceived fluency in native and nonnative speech

Fluency is an important part of research on second language learning, but most research on language proficiency typically has not included oral fluency as part of interaction, even though natural communication usually occurs in conversations. The present study considered aspects of turn-taking behavior as part of the construct of fluency and investigated whether these aspects differentially influence perceived fluency ratings of native and non-native speech. Results from two experiments using acoustically manipulated speech showed that, in native speech, too ‘eager’ (interrupting a question with a fast answer) and too ‘reluctant’ answers (answering slowly after a long turn gap) negatively affected fluency ratings. However, in non-native speech, only too ‘reluctant’ answers led to lower fluency ratings. Thus, we demonstrate that acoustic properties of dialogue are perceived as part of fluency. By adding to our current understanding of dialogue fluency, these lab-based findings carry implications for language teaching and assessmen

Non score-dependency: Theory and assessment

Untrained listeners demonstrate implicit knowledge of syntactic patterns and principles. Untrained generative music ability, for example singing, humming, and whistling, is a largely unconscious or intuitive application of these patterns and principles. From the viewpoint of embodied cognition, listening to music should evoke an internal representation or motor image which, together with the perception of organized music, should form the basis of musical cognition. Indeed, that is what listeners demonstrate when they sing, hum, or whistle familiar and unfamiliar tunes or when they vocally or orally improvise continuations to interrupted phrases. Research on vocal improvisation using continuations sung to an interrupted musical phrase, has shown that one’s cultural background influences the music generated. That should be the case for instrumentalists as well: when they play familiar or unfamiliar tunes by ear in different keys (transposition) or when they improvise variations, accompaniments, or continuations to interrupted phrases, the music they generate should reflect the same cognitive structures as their oral improvisations. This study is attempting to validate a test of (non) scoredependency that will enable assessment of the music student’s implicit knowledge of these structures during performance on the principal instrument

Dynamic portfolio and mortgage choice for homeowners

We investigate the impact of owner-occupied housing on financial portfolio and mortgage choice under stochastic inflation and real interest rates. To this end we develop a dynamic framework in which investors can invest in stocks and bonds with different maturities. We use a continuous-time model with CRRA preferences and calibrate the model parameters using data on inflation rates and equity, bond, and house prices. For the case of no short-sale constraints, we derive an implicit solution and identify the main channels through which the housing to total wealth ratio and the horizon affect financial portfolio choice. This solution is used to interpret numerical results that we provide when the investor has short-sale constraints. We also use our framework to investigate optimal mortgage size and type. A moderately risk-averse investor prefers an adjustable-rate mortgage (ARM), while a more risk-averse investor prefers a fixedrate mortgage (FRM). A combination of an ARM and an FRM further improves welfare. Choosing a suboptimal mortgage leads to utility losses up to 6%

User Research of a Voting Machine: Preliminary Findings and Experiences

This paper describes a usability study of the Nedap voting machine in the Netherlands. On the day of the national elections, 566 voters participated in our study immediately after having cast their real vote. The research focused on the correspondence between voter intents and voting results, distinguishing between usability (correspondence between voter intents and voter input) and machine reliability (correspondence between voter input and machine output). For the sake of comparison, participants also cast their votes using a paper ballot.\ud The machine reliability appeared to be 100%, indicating that, within our sample, all votes that had been cast were correctly represented in the output of the voting machine. Regarding usability, 1.4% of the participants had cast the wrong vote using the voting machine. This percentage was similar to that of the paper ballot. \ud Practical implications as well as experiences with this type of usability testing are discussed

What Can Be Learned from Computer Modeling? Comparing Expository and Modeling Approaches to Teaching Dynamic Systems Behavior

Computer modeling has been widely promoted as a means to attain higher order learning outcomes. Substantiating these benefits, however, has been problematic due to a lack of proper assessment tools. In this study, we compared computer modeling with expository instruction, using a tailored assessment designed to reveal the benefits of either mode of instruction. The assessment addresses proficiency in declarative knowledge, application, construction, and evaluation. The subscales differentiate between simple and complex structure. The learning task concerns the dynamics of global warming. We found that, for complex tasks, the modeling group outperformed the expository group on declarative knowledge and on evaluating complex models and data. No differences were found with regard to the application of knowledge or the creation of models. These results confirmed that modeling and direct instruction lead to qualitatively different learning outcomes, and that these two modes of instruction cannot be compared on a single “effectiveness measure”

Exploring two methods of usability testing: concurrent versus retrospective think-aloud protocols

Think-aloud protocols are commonly used for the usability testing of instructional documents, Web sites and interfaces. This paper addresses the benefits and drawbacks of two think-aloud variations: the traditional concurrent think-aloud method and the less familiar retrospective think-aloud protocols. It also offers an outline of a long-term research project designed to empirically investigate the value of both variants. The results of a first comparative study indicate that, although the two methods have distinct differences, they do seem to produce a similar outcome. A more detailed description of the results will be offered during the presentation