Analyzing Stimulus-Stimulus Pairing Effects on Preferences for Speech Sounds

Several studies have demonstrated effects of stimulus-stimulus pairing (SSP) on children's vocalizations, but numerous treatment failures have also been reported. The present study attempted to isolate procedural variables related to failures of SSP to condition speech sounds as reinforcers. Three boys diagnosed with autism-spectrum disorders participated. Phase 1 was designed to assess SSP effects on production of auditory stimuli via button pressing. When SSP failed to produce a preference for the target stimulus, we instituted a series of procedural manipulations intended to address potential reasons for failure. One participant preferred the target stimulus when given the opportunity to select preferred items for pairing prior to each session, but a subsequent reversal attempt produced ambiguous results. Two participants showed no consistent preference in Phase 1 and underwent a within-session reinforcer evaluation in Phase 2, in which alternative controlling variables were demonstrated by delivering preferred stimuli contingent on button pressing.     

FIRM SPECIFIC HUMAN CAPITAL AS AN EMPLOYER DISCIPLINE DEVICE

The inability of employers to monitor perfectly the level of effort of their employees is a potentially serious impediment to labor market efficacy. Indeed, a number of recent studies have concluded that this may lead to involuntary unemployment (Shapiro and Stiglitz [1984], Sparks [1986]); an inefficient sectoral allocation of workers (Oi [1990], Strand [1986]); and discrimination against productively identical workers (Bulow and Summers [1986]). This paper shows that the lock-in effect of firm-specific human capital can help alleviate problems of worker moral hazard and thereby promote labor market performance.     

Offenders as victims of crime?: an investigation into the relationship between criminal behaviour and victimization

Summary.  We consider the association between victimization and offending behaviour by using data from the Youth Lifestyles Survey. We consider the effect of violent and non-violent offending on the probability of being a victim of violent and non-violent crime and find a positive association between these by using univariate probit estimates. However, taking into account the endog- enous nature of offending and victimization via a bivariate probit model, we find that univariate estimates understate the association. We suggest that policy recommendations should only be informed by the bivariate analysis of the association between offending and victimization.     

Systems thinking

Evaluation is one of many fields where “systems thinking” is popular and is said to hold great promise. However, there is disagreement about what constitutes systems thinking. Its meaning is ambiguous, and systems scholars have made diverse and divergent attempts to describe it. Alternative origins include: von Bertalanffy, Aristotle, Lao Tsu or multiple aperiodic “waves.” Some scholars describe it as synonymous with systems sciences (i.e., nonlinear dynamics, complexity, chaos). Others view it as taxonomy—a laundry list of systems approaches. Within so much noise, it is often difficult for evaluators to find the systems thinking signal. Recent work in systems thinking describes it as an emergent property of four simple conceptual patterns (rules). For an evaluator to become a “systems thinker”, he or she need not spend years learning many methods or nonlinear sciences. Instead, with some practice, one can learn to apply these four simple rules to existing evaluation knowledge with transformative results.     

Combining key elements in training and research: Developing social work assessment theory and practice in partnership

This paper is based on a joint project between staff from a university department of social work and a local social services department and is jointly written by the four people involved. It reports on the development of a package of training and research over the past 5 years designed to improve standards of assessment in the work of child and family social workers employed by the authority. It analyses the positive reception given to the project both from practising social workers and from management. It contends that this model of combining theory, training, research and practice can and should be used more widely as a basis for supporting and developing professional social work. It discusses the introduction of a theoretical framework which anticipated the new national framework for assessment, but which has been used to critically assess it (as well as other models of assessment), and has involved experienced workers in their evaluation.     

(In)Sufficient?: ethnicity and foster care in English local authorities

This paper examines the place of ethnicity in local authority foster care in the context of the sufficiency duty to secure adequate local placements for looked after children. The analysis draws on two main sources, namely Office for Standards in Education, Children's Services and Skills (OFSTED's) annual survey of fostering agencies and inspection reports for around half the local authority fostering services in England. Sufficiency is gauged in two main ways, comparing numbers of black and minority ethnic (BME) foster carers first with numbers of BME looked after children and second, with local adult (age 25–64) populations. Statistical analysis shows very wide variation on both measures and a significant minority of authorities that perform poorly in terms of the ethnic diversity of their foster carers. Inspection reports also vary widely in the degree and nature of attention given to issues of ethnicity with many offering limited (and sometimes no) challenge to poor performance. These findings are discussed within the broader context of recent trends towards de‐emphasizing the significance of ethnicity in child welfare.     

Improved nonparametric tolerance intervals based on interpolated and extrapolated order statistics

The standard approach to construct nonparametric tolerance intervals is to use the appropriate order statistics, provided a minimum sample size requirement is met. However, it is well-known that this traditional approach is conservative with respect to the nominal level. One way to improve the coverage probabilities is to use interpolation. However, the extension to the case of two-sided tolerance intervals, as well as for the case when the minimum sample size requirement is not met, have not been studied. In this paper, an approach using linear interpolation is proposed for improving coverage probabilities for the two-sided setting. In the case when the minimum sample size requirement is not met, coverage probabilities are shown to improve by using linear extrapolation. A discussion about the effect on coverage probabilities and expected lengths when transforming the data is also presented. The applicability of this approach is demonstrated using three real data sets.     

Changing places: children of return migrants in Albania and their quest to belong

This study examines the experiences of children of return migrants to Albania following the economic crisis in Europe. Adopting a longitudinal approach in which participants were followed-up after a year and employing participative qualitative research methods, the study investigates how perceptions of local and translocal spaces and social relations interact to shape children’s (aged 7–12 years) sense of belonging to their parents’ homeland. Findings suggest that the children’s initial positioning is influenced by a perceived lack of everyday places of play and unsettled local interactions with peers. The research indicates further that, over time, children actively seek to inhabit and identify with their new surroundings and that meaning-making is shaped by experiences that transcend multiple localities. It documents how children of return migrants attain a sense of belonging via interacting with different physical and social contexts in a complex process which appears simultaneously facilitated and impeded by adults. Overall, the findings of this research suggest that children’s sense of belonging is negotiated in relation to multiple temporal and spatial frames of reference to which children attribute meaning.     

Benchmark Dose Risk Assessment for Formaldehyde Using Airflow Modeling and a Single-Compartment, DNA-Protein Cross-Link Dosimetry Model to Estimate Human Equivalent Doses

Formaldehyde induced squamous-cell carcinomas in the nasal passages of F344 rats in two inhalation bioassays at exposure levels of 6 ppm and above. Increases in rates of cell proliferation were measured by T. M. Monticello and colleagues at exposure levels of 0.7 ppm and above in the same tissues from which tumors arose. A risk assessment for formaldehyde was conducted at the CIIT Centers for Health Research, in collaboration with investigators from Toxicological Excellence in Risk Assessment (TERA) and the U.S. Environmental Protection Agency (U.S. EPA) in 1999. Two methods for dose-response assessment were used: a full biologically based modeling approach and a statistically oriented analysis by benchmark dose (BMD) method. This article presents the later approach, the purpose of which is to combine BMD and pharmacokinetic modeling to estimate human cancer risks from formaldehyde exposure. BMD analysis was used to identify points of departure (exposure levels) for low-dose extrapolation in rats for both tumor and the cell proliferation endpoints. The benchmark concentrations for induced cell proliferation were lower than for tumors. These concentrations were extrapolated to humans using two mechanistic models. One model used computational fluid dynamics (CFD) alone to determine rates of delivery of inhaled formaldehyde to the nasal lining. The second model combined the CFD method with a pharmacokinetic model to predict tissue dose with formaldehyde-induced DNA-protein cross-links (DPX) as a dose metric. Both extrapolation methods gave similar results, and the predicted cancer risk in humans at low exposure levels was found to be similar to that from a risk assessment conducted by the U.S. EPA in 1991. Use of the mechanistically based extrapolation models lends greater certainty to these risk estimates than previous approaches and also identifies the uncertainty in the measured dose-response relationship for cell proliferation at low exposure levels, the dose-response relationship for DPX in monkeys, and the choice between linear and nonlinear methods of extrapolation as key remaining sources of uncertainty.