https://www.mdu.se/

This thesis primarily looks at estimation error problems and other related issues arising in connection with portfolio optimization. With some available assets, a portfolio program or optimizer seeks to distribute a fixed amount of capital among these available assets to optimize some cost function. In this regard, Markowitz portfolio selection basis defines the variance of the portfolio return to being that of the portfolio risk and tries to find an allocation that reduces or minimizes the risk subject to a target mean or expected return. Should the mean return vector and the covariance matrix of returns for the underlying assets be known, the Markowitz problem is said to have a closed-form solution.

In practice, however, an estimation is made from historical data for unknown expected returns and the covariance matrix of the returns, and this brings into the domain several problems such as estimation problems and renders the Markowitz theory impracticable in real-life portfolio applications. Estimators necessary to remedy these problems would be made bare to show how possible it is to tackle such issues.

In the concept demonstration sections, the analysis starts with the price data of 40 stocks and the S\&P index. The efficient frontier is introduced and used to show how the estimators take effect.

Finally, implementation is made possible using the R Programming Language to demonstrate the necessary concepts with the conclusion presented at the end.

The global solution of a fuzzy linear system contains the crisp vector solution of a real linear system. So discussion about the global solution of a  fuzzy linear system  with a fuzzy number vector  in the right hand side and crisp a coefficient matrix  is considered. The advantage of the paper is developing a new algorithm to find the solution of such system by considering a global solution based upon the concept of a convex fuzzy numbers. At first the existence and uniqueness of the solution are introduced and then the related theorems and properties about the solution are proved in details. Finally the method is illustrated by solving some numerical examples.

This article presents a survey of techniques for ranking results in search engines, with emphasis on link-based ranking methods and the PageRank algorithm. The problem of selecting, in relation to a user search query, the most relevant documents from an unstructured source such as the WWW is discussed in detail. The need for extending classical information retrieval techniques such as boolean searching and vector space models with link-based ranking methods is demonstrated. The PageRank algorithm is introduced, and its numerical and spectral properties are discussed. The article concludes with an alternative means of computing PageRank, along with some example applications of this new method.

In this thesis we will explore the theory behind wavelets. The main focus is on the discrete wavelet transform, although to reach this goal we will also introduce the discrete Fourier transform as it allow us to derive important properties related to wavelet theory, such as the multiresolution analysis. Based on the multiresolution it will be shown how the discrete wavelet transform can be formulated and show how it can be expressed in terms of a matrix. In later chapters we will see how the discrete wavelet transform can be generalized into two dimensions, and discover how it can be used in image processing.

Syftet med mitt arbete är att belysa vilka metoder som finns för att eleven ska lära sig multiplikationstabellen, och vikten av utantill kunnande av multiplikationstabellen för eleven. Arbetet tar upp viktiga faktorer som påverkar kunnandet av multiplikationstabellen t.ex. miniräknaren och forskning om minnet. För att kunna uppfylla mitt syfte intervjuade jag tre erfarna pedagoger som uttalar sig om detta. Jag studerade vad pedagogerna anser om utantill kunnande av multiplikationstabellen, vilka metoder de använder för att lära ut tabellerna och vad de anser om miniräknaren som hjälpmedel. Jag har också använt mig av litteratur som handlar om minnet och vad som finns för grund inom forskningen för inlärningen av multiplikationstabellerna. Genom en kvalitativ analys av mitt resultat har jag kommit fram till att utantill kunnande av multiplikationstabellen förenklar och underlättar för eleven. Det ger ett bra verktyg för eleven för en fortsatt utveckling inom matematik.

As n-ary operations, generalizing Lie and Poisson algebras, arise in many different physical contexts, it is interesting to study general ways of constructing explicit realizations of such multilinear structures. Generically, they describe the dynamics of a physical system, and there is a need of understanding their quantization. Hom-Nambu-Lie algebras provide a framework that might be an appropriate setting in which n-Lie algebras (n-ary Nambu-Lie algebras) can be deformed, and their quantization studied. We present a procedure to construct (n + 1)-ary Hom-Nambu-Lie algebras from n-ary Hom-Nambu-Lie algebras equipped with a generalized trace function. It turns out that the implications of the compatibility conditions, that are necessary for this construction, can be understood in terms of the kernel of the trace function and the range of the twisting maps. Furthermore, we investigate the possibility of defining (n + k)-Lie algebras from n-Lie algebras and a k-form satisfying certain conditions. (C) 2011 American Institute of Physics. [doi:10.1063/1.3653197]

Several recent textbook studies focus on opportunities to learn reasoning-and-proving. They typically investigate the extent to which justifications are general proofs and what opportunities exist for learning important elements of mathematical reasoning. In this paper, I discuss how a particular analytical framework for this might be refined. Based on an in-depth analysis of certain textbook passages in upper secondary calculus textbooks, I make an account for analytical issues encountered during this process and identify aspects of reasoning-and-proving in textbooks that might be missed unless the framework is refined. Among them there are characterizations of generality, use of different representations, logical and mathematical structure, and ordering of material and student activities. Finally, implications beyond textbook research are discussed.

Students’ difficulties with proof, scholars’ calls for proof to be a consistent part of K-12 mathematics, and the extensive use of textbooks in mathematics classrooms motivate investigations on how proof-related items are addressed in mathematics textbooks. We contribute to textbook research by focusing on opportunities to learn proof-related reasoning in integral calculus, a key subject in transitioning from secondary to tertiary education. We analyze expository sections and nearly 2000 students’ exercises in the four most frequently used Finnish and Swedish textbook series. Results indicate that Finnish textbooks offer more opportunities for learning proof than do Swedish textbooks. Proofs are also more visible in Finnish text-books than in Swedish materials, but the tasks in the latter reflect a higher variation in nature of proof-related reasoning. Our results are compared with methodologically similar U.S. studies. Consequences for learning and transition to university mathematics, as well as directions for future research, are discussed.

Competence in mental arithmetic is recognised by many as essential to be active participants in the fast flowing, high technological society we live in today.  Many have noticed pupils’ unwillingness to set their calculators aside and practice this aspect of mathematics when possible.  Furthermore, some studies show that pupils’ ability to compute mentally deteriorates as they pass through the school system.  Through testing classes in a Swedish obligatory school and an upper secondary school, the aim of this thesis is to see if the goals set by The National [Swedish] Agency for Education regarding mental arithmetic, are being fulfilled.  Through using questionnaires to collect the strategies and ideas of the pupils, a wide range of problematic mathematical misconceptions became evident.  These are highlighted since they are important aspects teachers should be aware of.  The results of this study show that the obligatory school classes are far from reaching the goals set for them whereas the upper secondary classes show good results.  Furthermore, there is an apparent improvement in their progression, resulting in a fulfilment the official goals.  Many pupils however, seem reluctant to rely on their mental arithmetic capabilities and resort to algorithmic strategies.  Other problems to emerge are in carrying out table calculations and in a lack of number sense when deeming if the answers are reasonable.   

Sambandet mellan de fyra räknesätten är en del i utvecklingen av den matematiska förståelsen. Syftet med denna studie är att analysera hur ett antal olika läromedel i matematik riktade till årskurs 1-3 tar upp dessa samband. Med läromedel menas då läroböcker, samt tillhörande lärarhandledningar. Resultatet visar att flertalet av de analyserade läromedlen inte tar upp alla samband, medan ett fåtal tar upp alla samband men i olika stor omfattning. Dessutom visar analysen hur viktig lärarhandledningen är för att ge eleverna fler övningstillfällen i att träna de fyra sambanden, eftersom en stor del av dessa tillfällen förekommer i lärarhandledningen och inte i läroböckerna. Lärare som endast följer ett enskilt läromedel i sin undervisning kan alltså gå miste om mycket när det gäller sambandet mellan de fyra räknesätten.

Considered are operators that leave the set of non-invertible (in the sense of Ehrenpreis) distributions stable. They simultaneously generalise the operation of convolution by a distribution with compact support and the operation of multiplication by a real analytic function; they are here called pseudo-convolutions since they also generalise pseudo-differential operators. (It is shown that the elliptic real analytic pseudo-differential operators leave both the non-invertible and the invertible distributions invariant.) But when the condition of real-analyticity is relaxed, such operators may map a non-invertible distribution to one invertible -- given that the invertibility in both cases concerns the same function space. By varying the space, however, one can measure the 'loss of non-invertibily' that a non-analytic perturbation may introduce. This phenomenon is here studied using the Beurling classes of functions and measuring the regularity of operator symbols in the Denjoy-Carleman sense; the Gevrey case turns out particularly simple.

Numerical time series, but especially periodic such, are characterized up to pertinent symmetries by families of norms. The electricity consumption by a household, recorded daily during a month’s time, say, may then be encoded in a sequence of numbers; for example, as follows: the mean daily consumption, the mean daily variation of the consumption, the variation of the variation, the variation of the variation of the variation, etc. Now, replacing each of these numbers by the digits 0, 1, or 2, to say that a number is “low”, “medium”, or “high”, in relation to a collection of households, one naturally partitions the collection by the strings of these three digits; the household labeled 102   has then medium daily consumption, low daily variation, but high variation of variation, etc. We generally discuss this innocent idea and examine it in three ways: by way of toy examples, through its mathematical model (in detail presented elsewhere) and by accordingly classifying some actual electricity consumption data.

Denna studie har syftet att få kunskap om hur stor andel av uppgifterna som kan klassas som matematiska problem i två matematikböcker för årskurs fem. Tidigare forskning visar att det finns få matematiska problem i de matematiska läroböckerna i både grundskola och gymnasium. Resultaten grundar sig i analysfrågor som skapades utifrån vår tolkning av tidigare forskning av Brehmer, Ryve och Steenbrugge (2016) där de lyfter sina tankar och resonemang gällande matematiskt problem utifrån Lithners (2006) kreativa och imitativa resonemang. Genom en kvantitativ ansats av två läroböcker kom vi fram till att den ena boken totalt hade 474 uppgifter och 10 matematiska problem, medan den andra boken hade 759 uppgifter och 7 matematiska problem. Resultaten utifrån analysen visar att andelen matematiska problem är låg jämfört med antal uppgifter, vilket diskuteras utifrån hur viktig problemlösningsförmågan anses vara för elever att utveckla.

Ethno-racial workplace segregation increases already existing ethno-racial inequality. While previous research has identified discriminatory employers as drivers of workplace segregation, this study addresses the role of the employees. Sociological and social psychological theory suggest that people prefer to surround themselves with people who positively confirm their social identity or who contribute with higher group status. Through web-based surveys, we measure employee attitudes and preferences concerning ethno-racial workplace diversity, to what extent they differ by ethnicity/race, and if they contain intersectional patterns. Thereafter, we use simulation models to analyze the consequences for workplace segregation that these preferences would have, if realized. The main survey results showed that all ethno-racial groups favored their own in-group as colleagues, especially European Americans. As a secondary choice, the respondents preferred the out-group with the highest labor market status. Intersectional patterns were identified, as minority women were preferred as colleagues over minority men. Our simulation model, based on the results of two surveys on stated vs. indirectly revealed preferences, showed that employee preferences were at best not diverse enough to desegregate workplaces. When based on the most common preferences (i.e. excluding a few outliers), the simulations even suggested that these preferences can cause segregation. We relate these findings to Schelling's model of segregation.

Syftet med studien är att studera vilken syn sju elever i årskurs fyra och fem har på konkret material i matematikundervisningen. Metoden som användes för att samla in data var sju semistrukturerade elevintervjuer. Resultatet visar att elevernas syn på användning av konkret material är att det ska ge dem ett visuellt stöd för konkretisering av abstrakt matematik där siffror och symboler dominerar. Resultatet visar även att eleverna tycker att konkret material ska ingå i undervisningen. Slutsatser som kan dras från den här studien stämmer överens med det teoretiska ramverk som används i tolkning av data, om eleverna lär sig med hjälp av modeller eller om elever använder sina kunskaper till att konstruera modeller. En konsekvens av denna studie kan vara att lärare behöver utveckla sin ämnesdidaktiska kompetens så att undervisningen harmonierar med centralt innehåll för årskurs fyra till sex i den rådande läroplanen för skolan.

We examine methods for studying polarons in metal oxides with density functional theory (DFT), using the example of cerium dioxide and the functionals, local density approximation + U (LDA+U), generalized gradient approximation + U (GGA+U) in the Perdew-Burke-Ernzerhof parametrization (PBE+U), as well as the hybrid functionals B3LYP, Heyd?Scuseria?Ernzerhof (HSE)03, HSE06, and PBE0. We contrast the four polaron energies commonly reported in different parts of the literature: formation energy, localization/relaxation energy, density-of-states level, and polaron-hopping activation barrier. Qualitatively, all these functionals predict "small" (Holstein) polarons on the scale of a single lattice site, although LDA+U and GGA+U are more effective than the hybrids at localizing the Ce 4f electrons. The improvements over pure LDA/GGA appear because of changes in the filled Ce 4f states when using LDA/GGA+U but due to changes in the empty Ce 4f states when using the hybrids. DFT is shown to have sufficient correlation to predict both adiabatic and (approximate) diabatic hopping barriers. Overall, LDA+U = 6 eV provides the best description in comparison to the experiment, followed by GGA+U = 5 eV. The hybrids are worse, tending to overestimate the gap and significantly underestimate the polaron-hopping barriers.

Game theory is a formal approach to behavior that focuses on the strategic aspect of situations. The game theoretic approach originates in economics but has been embraced by scholars across disciplines, including many philosophers and biologists. This approach has an important weakness: the strategic aspect of a situation, which is its defining quality in game theory, is often not its most salient quality in human (or animal) cognition. Evidence from a wide range of experiments highlights this shortcoming. Previous theoretical and empirical work has sought to address this weakness by considering learning across an ensemble of multiple games simultaneously. Here we extend this framework, incorporating artificial neural networks, to allow for an investigation of the interaction between the perceptual and functional similarity of the games composing the larger ensemble. Using this framework, we conduct a theoretical investigation of a population that encounters both stag hunts and prisoner's dilemmas, two situations that are strategically different but which may or may not be perceptually similar.

Ineffective, aversive and harmful medical treatments are common cross-culturally, historically and today. Using evolutionary game theory, we develop the following model to explain their persistence. Humans are often incapacitated by illness and injury, and are unusually dependent on care from others during convalescence. However, such caregiving is vulnerable to exploitation via illness deception, whereby people feign or exaggerate illness in order to gain access to care. Our model demonstrates that aversive treatments can counter-intuitively increase the range of conditions where caregiving is evolutionarily viable, because only individuals who stand to gain substantially from care will accept the treatment. Thus, contemporary and historical “ineffective” treatments may be solutions to the problem of allocating care to people whose true need is difficult to discern.

BACKGROUND: Medical treatments with no direct effect (like homeopathy) or that cause harm (like bloodletting) are common across cultures and throughout history. How do such treatments spread and persist? Most medical treatments result in a range of outcomes: some people improve while others deteriorate. If the people who improve are more inclined to tell others about their experiences than the people who deteriorate, ineffective or even harmful treatments can maintain a good reputation.

OBJECTIVE: The intent of this study was to test the hypothesis that positive outcomes are overrepresented in online medical product reviews, to examine if this reputational distortion is large enough to bias people's decisions, and to explore the implications of this bias for the cultural evolution of medical treatments.

METHODS: We compared outcomes of weight loss treatments and fertility treatments in clinical trials to outcomes reported in 1901 reviews on Amazon. Then, in a series of experiments, we evaluated people's choice of weight loss diet after reading different reviews. Finally, a mathematical model was used to examine if this bias could result in less effective treatments having a better reputation than more effective treatments.

RESULTS: Data are consistent with the hypothesis that people with better outcomes are more inclined to write reviews. After 6 months on the diet, 93% (64/69) of online reviewers reported a weight loss of 10 kg or more while just 27% (19/71) of clinical trial participants experienced this level of weight change. A similar positive distortion was found in fertility treatment reviews. In a series of experiments, we show that people are more inclined to begin a diet with many positive reviews, than a diet with reviews that are representative of the diet's true effect. A mathematical model of medical cultural evolution shows that the size of the positive distortion critically depends on the shape of the outcome distribution.

CONCLUSIONS: Online reviews overestimate the benefits of medical treatments, probably because people with negative outcomes are less inclined to tell others about their experiences. This bias can enable ineffective medical treatments to maintain a good reputation.

In different applications (i.e., information retrieval, filteringor analysis), it is useful to detect similar terms and to provide the possibilityto use them jointly. Clustering of terms is one of the methods whichcan be exploited for this. In our study, we propose to test three methodsdedicated to the clustering of terms (hierarchical ascendant classification,Radius and maximum), to combine them with the semantic distance algorithmsand to compare them through the results they provide whenapplied to terms from the pharmacovigilance area. The comparison indicatesthat the non disjoint clustering (Radius and maximum) outperformthe disjoint clusters by 10 to up to 20 points in all the experiments.

The purpose of this activity is to investigate how the PageRank algorithm behaves in relation to the damping factor when applied to small graphs and certain special graph types. The PageRank algorithm involves the calculation of eigenvalues and eigenvectors of the Google matrix for both directed and undirected graphs. This discussion will focus on all directed graphs with up to four vertices and select special graphs. Our primary objective is to observe how the damping factor influences the dominant eigenvector for each graph and, consequently, how it impacts PageRank. We have calculated PageRank for all the graphs and conducted an analysis, particularly focusing on the effect of the damping factor, denoted as "c," in our discussions.

To compute the PageRank algorithm, we constructed a probability matrix for all the graphs and performed the calculations using MATLAB. This process yielded eigenvalues and eigenvectors associated with the Google matrix. The theoretical section of this thesis encompasses the PageRank theory, including essential proofs, theorems, and definitions that serve as foundational elements throughout the thesis. Additionally, we delve into the historical context and practical applications of PageRank.

In our study, we present a comparative analysis of the results, specifically examining the impact of a damping factor on the dominant PageRank eigenvector. 

Division of labor and division of knowledge are so important and common in society today that it is difficult to imagine a functional society where everyone knows the same things and performs the same tasks. In such a society everyone grows, or gathers, and prepares their own food, makes their own tools, builds their own house, and so on.

Cultural evolution is the field of research that studies the creation and diffusion of ideas and societies. It is very uncommon for these studies to take into account the effects of specialization. This thesis will show that specialization is of great importance to cultural evolution.

The thesis is divided into two parts: The first is an introduction to studies of specialization and division of labor. The thesis begins with an interdisciplinary survey of the research on division of labor and specialization, including both theoretic and empirical studies. Next is an introduction to modeling specialization and division of labor. This includes a general framework and a number of basic models of different aspects of specialization and division of labor.

Part two consists of four papers. The first paper studies the interaction between specialization and cultural cumulation. The second and third papers examine cultural cumulation, specifically the circumstances under which cultural knowledge increases and how cultural knowledge is distributed in the population. The last paper is a mathematical model of how specialization of knowledge (i.e. higher education) leads to social stratification.

This paper studies the interaction between specialization and cul-tural evolution. Four key components are identified from publishedempirical studies: Culture, Specialization, Production and Popula-tion. Mathematical models are used to investigate the interactionsbetween the components and the behavior of the entire system. Theresults show that specialization is both a cause and an outcome of cul-tural cumulation, which creates feedback cycles in cultural evolution.The feedback cycles can explain the drastic increase in innovation ratewe have observed throughout human history. Specialization is there-fore argued to be an integral part in understanding cultural evolution.

Social stratification is present in all modern societies. Do income dif-ferences simply reflect inherited differences in individual abilities and re-sources? If not, why does not everyone choose strategies that lead to highincome? This paper shows that the psychological phenomenon known astemporal discounting will lead to differences in educational attainmentand therefore social stratification in any society where the demand forworkers with a higher level of education is higher than for those witha lower level. The model is used to predict income differences betweenpeople with and without college education in seven developed countries,based only on official statistics of the cost and length of college education.The model explains 93 percent of the variance, strongly suggesting thattemporal discounting is a major factor behind income differences.

The demographic and ecological success of our species is frequently attributed to our capacity for cumulative culture. However, it is not yet known how humans combine social and asocial learning to generate effective strategies for learning in a cumulative cultural context. Here we explore how cumulative culture influences therelative merits of various pure and conditional learning strategies, including pure asocial and social learning, critical social learning, conditional social learning and individual refiner strategies. We replicate the Rogers’ paradox in the cumulative setting. However, our analysis suggests that strategies that resolved Rogers’ Paradoxin a non-cumulative setting may not necessarily evolve in a cumulative setting, thus different strategies will optimize cumulative and non-cumulative cultural learning.

Syftet med vårt examensarbete är att söka samband mellan lärares inställning och undervisningsmetoder och elevernas inställning till ämnet matematik. Vi använde oss av både kvalitativa och kvantitativa metoder i vår undersökning. Vi genomförde en enkätundersökning bland elever i år tre och år fyra vid två olika skolor samt intervjuade deras lärare.

Resultatet av undersökningen visade att där läraren inte är bekväm i ämnet utan bara använder sig av matematikboken i undervisningen, tycker inte eleverna att matematik är särskilt roligt. Däremot i de klasser där läraren inser vikten av en varierande matematikundervisning och ett varierat arbetssätt, tycker eleverna att matematik är roligt. Detta visar att det är viktigt att variera undervisningen och behålla en pedagogisk professionalism där man förbiser sina egna åsikter för elevernas bästa.

The ability to acquire knowledge and skills from others is widespread in animals and is commonly thought to be responsible for the behavioural traditions observed in many species. However, in spite of the extensive literature on theoretical analyses and empirical studies of social learning, little attention has been given to whether individuals acquire knowledge from a single individual or multiple models. Researchers commonly refer to instances of sons learning from fathers, or daughters from mothers, while theoreticians have constructed models of uniparental transmission, with little consideration of whether such restricted modes of transmission are actually feasible. We used mathematical models to demonstrate that the conditions under which learning from a single cultural parent can lead to stable culture are surprisingly restricted ( the same reasoning applies to a single social-learning event). Conversely, we demonstrate how learning from more than one cultural parent can establish culture, and find that cultural traits will reach a nonzero equilibrium in the population provided the product of the fidelity of social learning and the number of cultural parents exceeds 1. We discuss the implications of the analysis for interpreting various findings in the animal social-learning literature, as well as the unique features of human culture.

Previous research shows that individuals with Asperger syndrome or high-functioning autism tend to have impaired processing of humor and laugh at things that are not commonly found funny. Here the relationship between humor styles and the broader autism phenotype was investigated in a sample of the general population. The autism-spectrum quotient (AQ) and the humor styles questionnaire (HSQ) were administered to six hundred US participants recruited through an Internet-based service. On the whole, high scores on AQ were negatively related to positive humor styles and unrelated to negative humor styles. However, AQ subscales representing different autism-spectrum traits exhibited different patterns. In particular, the factor "poor mind-reading" was associated with higher scores on negative humor styles and the factor "attention to detail" was associated with higher scores on all humor styles, suggesting a more nuanced picture of the relationship between autism-spectrum traits and humor.

At the end of their thoughtful target article, Andersson and Read conclude that formal models of cultural evolution are “useful but must be kept in perspective.” As a mathematician with a great interest in social science, I have some experience of working with such models. Based on this experience, I very much agree with the “but” part of the above conclusion. I see a clear tendency in the cultural evolution literature to put too much trust in the value of formal models.

Experiments on economic games typically fail to find positive reputational effects of using peer punishment of selfish behavior in social dilemmas. Theorists had expected positive reputational effects because of the potentially beneficial consequences that punishment may have on norm violators’ behavior. Going beyond the game-theoretic paradigm, we used vignettes to study how various social factors influence approval ratings of a peer who reprimands a violator of a group-beneficial norm. We found that ratings declined when punishers showed anger, and this effect was mediated by perceived aggressiveness. Thus the same emotions that motivate peer punishers may make them come across as aggressive, to the detriment of their reputation. However, the negative effect of showing anger disappeared when the norm violation was sufficiently severe. Ratings of punishers were also influenced by social distance, such that it is less appropriate for a stranger than a friend to reprimand a violator. In sum, peer punisher ratings were very high for a friend reprimanding a severe norm violation, but particularly poor for a stranger showing anger at a mild norm violation. We found no effect on ratings of whether the reprimand had the beneficial consequence of changing the violator’s behavior. Our findings provide insight into how peer punishers can avoid negative reputational effects. They also point to the importance of going beyond economic games when studying peer punishment. 

In one conception of cultural evolution, the evolutionary success of cultural units that are transmitted from individual to individual is determined by forces of cultural selection. Here we argue that it is helpful to distinguish between several distinct phases of the transmission process in which cultural selection can operate, such as a choose-toreceive phase, an encode-and-retrieve phase, and a choose-to-transmit phase. Here we focus on emotional selection in cultural transmission of urban legends, which has previously been shown to operate in the choose-to-transmit phase. In a series of experiments we studied serial transmission of stories based on urban legends manipulated to be either high or low on disgusting content. Results supported emotional selection operating in all three phases of cultural transmission. Thus, the prevalence of disgusting urban legends in North America may be explained by emotional selection through a multitude of pathways. 

Summary.: The Braess Paradox is the counterintuitive fact that creation of a shortcut may make travel slower. As each driver seeks to minimize his/her travel time, the shortcut may become so popular that it causes congestion elsewhere in the road network, thereby increasing the travel time for everyone. We extend the paradox by considering a shortcut that is a single-lane but two-way street. The conflict about which drivers get to use the single-lane shortcut is an example of a game theoretic situation known as Chicken, which merges with the Braess Paradox into the novel Chicken Braess Paradox: meeting traffic may make travel quicker. 

Prior research has linked religiosity to certain forms of self-enhancement. We extend this literature by three studies linking religiosity to the well-established better-than-average effect (BAE). First, a reanalysis of self-judgments of desirable characteristics in 15 nations showed that the BAE was stronger in more religious countries, even taking into account gross domestic product, interdependence, and economic inequality. Second, in two online surveys totaling 1,000 Americans, the BAE was stronger among more religious individuals. Several observations indicated that this relation was due to individuals self-stereotyping with respect to their religious in-groups. In particular, the relation was restricted to characteristics on the warmth dimension, consistent with the religious stereotype, and the average religious in-group member tended to be judged even more favorably than self. The latter phenomenon, which we term humble self-enhancement, is consistent with other studies linking stronger religiosity to greater favoritism of the religious in-group and greater derogation of religious out-groups. 

A strategy activated in one task may be transferred to subsequent tasks and prevent activation of other strategies that would otherwise come to mind, a mechanism referred to as procedural priming. In a novel application of procedural priming we show that it can make or break cognitive illusions. Our test case is the 1/k illusion, which is based on the same unwarranted mathematical shortcut as the MPG illusion and the time-saving bias. The task is to estimate distances between values of fractions on the form 1/k. Most people given this task intuitively base their estimates on the distances between the denominators (i.e., the reciprocals of the fractions), which may yield very poor estimations of the true distances between the fractions. As expected, the tendency to fall for this illusion is related to cognitive style (Study 1). In order to apply procedural priming we constructed versions of the task in which the illusion is weak, in the sense that most people do not fall for it anymore. We then gave participants both “strong illusion” and “weak illusion” versions of the task (Studies 2 and 3). Participants who first did the task in the weak illusion version would often persist with the correct strategy even in the strong illusion version, thus breaking the otherwise strong illusion in the latter task. Conversely, participants who took the strong illusion version first would then often fall for the illusion even in the weak illusion version, thus strengthening the otherwise weak illusion in the latter task.

Previous research has demonstrated that unfairness judgments of resource allocations become more complex when there are more than two recipients. In order to explain some of this complexity, we propose a set of psychological mechanisms that may underlie four different choices of maximally unfair resource allocations (MUA): Self-Single-Loser, Self-One-Loser-of-Many, Self-Single-Winner, and Self-One-Winner-of-Many. From this psychological theory, several predictions are derived and tested in vignette studies involving a total of 708 participants recruited online using MTurk. As predicted by our theory, (1) choices of MUA where there is a single loser were much more common when the allocated resource was of negative rather than positive valence, and (2) the amount of egoistic bias individuals exhibited when judging the unfairness in receiving a small rather than a large share in a non-extreme multi-party allocation was predicted by their choices of MUA. These findings suggest that an individual’s choice of MUA reveals some generally relevant principles of how unfairness is perceived in multi-party allocations. This opens up new lines of inquiry, especially regarding research on social dilemmas and social value orientation.

In studies of long-term memory of multi-digit numbers the leading digit tends to be recalled correctly more often than less significant digits, which has been interpreted as evidence for an analog magnitude encoding of the numbers. However, upon closer examination of data from one of these studies we found that the distribution of recall errors does not fit a model based on analog encoding. Rather, the data suggested an alternative hypothesis that each digit of a number is encoded separately in long-term memory, and that encoding of one or more digits sometimes fails due to insufficient attention in which case they are simply guessed when recall is requested, with no regard for the presented value. To test this hypothesis of nominal encoding with value-independent mistakes, we conducted two studies with a total of 1,080 adults who were asked to recall a single piece of numerical information that had been presented in a story they had read earlier. The information was a three-digit number, manipulated between subjects with respect to its value (between 193 and 975), format (Arabic digits or words), and what it counted (baseball caps or grains of sand). Results were consistent with our hypothesis. Further, the leading digit was recalled correctly more often than less significant digits when the number was presented in Arabic digits but not when the number was presented in words; our interpretation of this finding is that the latter format does not focus readers’ attention on the leading digit.

In three web-based experiments, we show that both actual poverty and experimentally induced (imagined) poverty create a preference for greater inequality. Study 1, a cross-national comparison between Americans and Swedes, showed that respondents who were actually poor and those who were experimentally induced to imagine that they were poor tended to express a heightened preference for greater inequality, and for a higher proportion of poor citizens. Study 2 replicated the effects using different procedures. Study 3 showed that imagining oneself being poor increases preferences for a greater proportion of poor people, but imagining oneself being rich does not increase preferences for a greater proportion of rich people. This poverty prefers company effect might affect support for policies aiming at reducing the number of poor people.

Does selfishness pay in the long term? Previous research has indicated that being otherish rather than selfish has positive consequences for psychological well-being, physical health, and relationships. Here we instead examine the consequences for individuals’ income and number of children, as these are the currencies that matter most in theories that emphasize the power of self-interest, namely economics and evolutionary thinking. Drawing on both cross-sectional (Studies 1 and 2) and panel data (Studies 3 and 4), we find that otherish individuals tend to have more children and higher income than selfish individuals. An additional survey (Study 5) of lay beliefs about how self-interest impacts income and fertility gives an indication of why selfish people persist in their behaviour even though it leads to poorer outcomes: people generally expect selfish individuals to have higher incomes. Our findings have implications for lay decisions about the allocation of scarce resources, as well as for economic and evolutionary theories of human behavior.

Drawing on the theory of the Big Two content dimensions of social judgmentagency and communionthe author proposes that several findings about partisan differences in the United States can be integrated into one hypothesis: Republicans tend to put greater value on agency, while Democrats put greater value on communion. Moreover, on the basis of these values, Republicans and Democrats should judge their own groups as particularly superior on agency and communion, respectively. These hypotheses gained support in three studies on partisan values and ingroup bias, suggesting that the agency-communion framework may be useful for researchers studying how political groups differ in their worldviews, biases, and attitudes.