Three-dimensional disordered conductors in a strong magnetic field: surface states and quantum Hall plateaus

We study localization in layered, three-dimensional conductors in strong magnetic fields. We demonstrate the existence of three phases - insulator, metal and quantized Hall conductor - in the two-dimensional parameter space obtained by varying the Fermi energy and the interlayer coupling strength. Transport in the quantized Hall conductor occurs via extended surface states. These surface states constitute a subsystem at a novel critical point, which we describe using a new, directed network model.Comment: 4 pages (PostScript) replaced due to compression error, slightly shortened version to appear in PR

Nonverbal imitation skills in children with specific language delay

Research in children with language problems has focussed on verbal deficits, and we have less understanding of children's deficits with nonverbal sociocognitive skills which have been proposed to be important for language acquisition. This study was designed to investigate elicited nonverbal imitation in children with specific language delay (SLD). It is argued that difficulties in nonverbal imitation, which do not involve the processing of structural aspects of language, may be indicative of sociocognitive deficits. Participants were German-speaking typically developing children (n=60) and children with SLD (n=45) aged 2-3 ½ years. A novel battery of tasks measured their ability to imitate a range of nonverbal target acts that to a greater or lesser extent involve sociocognitive skills (body movements, instrumental acts on objects, pretend acts). Significant group differences were found for all body movement and pretend act tasks, but not for the instrumental act tasks. The poorer imitative performance of the SLD sample was not explained by motor or nonverbal cognitive skills. Thus, it appeared that the nature of the task affected children's imitation performance. It is argued that the ability to establish a sense of connectedness with the demonstrator was at the core of children's imitation difficulty in the SLD sample

Direct Evidence in Risk Attitudes and Migration

It has long been hypothesized that individuals'' migration propensities depend on their attitudes towards risk, but the empirical evidence, to the extent that it exists, has been indirect. In this paper, we use newly available data from the German Socio-Economic Panel to measure directly the relationship between migration propensities and attitudes towards risk. We find that individuals who are more willing to take risks are more likely to migrate between labor markets in Germany. This result is robust to stratifying by age, sex, education, national origin, and a variety of other demographic characteristics. The effect is substantial relative to the unconditional migration propensity and compared to the conventional determinants of migration. We find no evidence that these findings are the result of reverse causality.education, training and the labour market;

Direct Evidence on Risk Attitudes and Migration

Geographic mobility is important for the functioning of labor markets because it brings labor resources to where they can be most efficiently used. It has long been hypothesized that individuals' migration propensities depend on their attitudes towards risk, but the empirical evidence, to the extent that it exists, has been indirect. In this paper, we use newly available data from the German Socio-Economic Panel to measure directly the relationship between migration propensities and attitudes towards risk. We find that individuals who are more willing to take risks are more likely to migrate between labor markets in Germany. This result is robust to stratifying by age, sex, education, national origin, and a variety of other demographic characteristics, as well as to the level of aggregation used to define geographic mobility. The effect is substantial relative to the unconditional migration propensity and compared to the conventional determinants of migration. We also find that being more willing to take risks is more important for the extensive than for the intensive margin of migration.Migration, attitudes, risk

Body movement imitation and early language as predictors of later social communication and language outcomes: A longitudinal study

Background and aims: Over recent decades much research has focused on detecting predictors of different language trajectories in children with early language delay but there has been very little exploration of social communication trajectories in these children. We report a longitudinal study that investigated the predictive value and clinical significance of elicited body movement imitation and language for later social communication and language outcome in Late Talkers. Methods: Participants were 29 German-speaking children who were identified with delayed onset and progression of language at two years and followed up at four years. Novel assessments of posture and gesture imitation were administered at Time 1, together with standardised language measures. All body movement imitation items involved self-other mappings, assumed to rely on sociocognitive capacities. At Time 2, children were assessed on standard language tests, together with parental reports of social communication. Results: Early language skills at Time 1 were significantly associated with later language outcome and body movement imitation skills at Time 1 with later social communication outcome. Logistic regression analyses revealed that body movement imitation as well as language at Time 1 added significantly to the prediction of language outcome at Time 2, whereas only body movement imitation made a significant contribution to the prediction of social communication outcome at Time 2. Conclusions and implications: Theoretically, results highlight the need to account for the heterogeneity of different language and communication trajectories in children with early language delay and point to the importance of sociocognitive difficulties observed in some of these children. Clinically, this study demonstrated that body movement imitation measures have the potential to improve the identification of pre-schoolers who are at risk of later social communication and language problems

Investigating sociocognitive skills in 2 and 3 year old German-speaking children with typical and delayed language development

It has been estimated that 7% of children have language impairments. The early identification of these problems has been recognised as very important to prevent consequential social, behaviour and educational problems. By the point when children start to acquire words, some of their sociocognitive skills are already quite elaborated and others' arc developing rapidly. During the last decades the relationship between several sociocognitive skills and language has been examined in depth in the areas of typical child development as well as in children with autism. It has been found that these interpersonal skills are strongly associated with early language and communication abilities and further predict later language skills in typically developing children as well as children with autism. More recently, children's knowledge of other person's motivational and intentional states has become a focus of interest and has been predicted to be crucial for the acquisition of communication and language. This knowledge is inseparably connected with the acquisition of sociocognitivc skills. However, the relation between sociocognitive skills and specific deficits in language has been less extensively explored, but Chiat and Roy currently have begun to look at early processing skills that are known to underpin language development as predictors of later language disorders. Grown out of their research with English-speaking children, this project primarily aimed to investigate whether, and to what extent, performance on assessments which tap a range of interrelated sociocognitive skills differ between groups of 2 and 3 year old German- speaking children with typical and delayed language development. Furthermore, two novel assessments were specifically designed for this project to additionally investigate children's imitation skills. It was found that the groups of language delayed children clearly showed deficits in all sociocognitive skills in comparison to the groups of typically developing children, though further analyses revealed overlaps between the performance of some individual cases of clinical children with the performance of the control children. In addition, mismatchs between sociocognitivc abilities and specific linguistic abilities were observed in the individual profiles of some language delayed children. These findings are discussed in terms of possible impacts of the discovered sociocognitive deficits on the acquisition of language and communication, focussing on the role of imitation for the onset of children's vocabulary- spurt