Contributions of Look Duration and Gaze Shift Patterns to Infants’ Novelty Preferences

Data from 72 infants, tested using a serial paired‐comparison paradigm, were analyzed to better understand infant novelty preferences. Infants between the ages of 15 and 26 weeks were tested in three studies with familiar stimuli displayed adjacent to novel stimuli on each trial. Differences in look duration, look number, and gaze shifts directed at novel versus familiar stimuli were assessed to measure their contributions to group and individual novelty preferences. Infants produced longer looks for novel stimuli in all three studies, and stimulus differences in look duration accounted for more than 50% of the variability in individual novelty preferences. Infants that produced more looks to novel rather than familiar stimuli did not produce overall novelty preferences unless they also looked longer at novel stimuli. Gaze shift patterns did not predict individual novelty preferences, and novel stimuli did not determine where infants looked. The infants’ visual exploration was constrained by memories for the direction of the previous look as well as by the attention‐holding features of novel stimuli.     

Mirror, mirror on the wall: reflections from failure to establish a truly uniform national health care policy

When the author gazed into the proverbial mirror and asked if the U.S. health care system was the fairest of them all, it shattered. In this article, Thompson tells why the system is broken and what failure to fix it means to physician executives. He suggests that we, as Americans, must reinvent ourselves by realigning our value systems and and stifling our obsession with profit before trying to reinvent health care.     

Recognizing Structural Nonidentifiability: When Experiments Do Not Provide Information About Important Parameters and Misleading Models Can Still Have Great Fit

In the quest to model various phenomena, the foundational importance of parameter identifiability to sound statistical modeling may be less well appreciated than goodness of fit. Identifiability concerns the quality of objective information in data to facilitate estimation of a parameter, while nonidentifiability means there are parameters in a model about which the data provide little or no information. In purely empirical models where parsimonious good fit is the chief concern, nonidentifiability (or parameter redundancy) implies overparameterization of the model. In contrast, nonidentifiability implies underinformativeness of available data in mechanistically derived models where parameters are interpreted as having strong practical meaning. This study explores illustrative examples of structural nonidentifiability and its implications using mechanistically derived models (for repeated presence/absence analyses and dose–response of Escherichia coli O157:H7 and norovirus) drawn from quantitative microbial risk assessment. Following algebraic proof of nonidentifiability in these examples, profile likelihood analysis and Bayesian Markov Chain Monte Carlo with uniform priors are illustrated as tools to help detect model parameters that are not strongly identifiable. It is shown that identifiability should be considered during experimental design and ethics approval to ensure generated data can yield strong objective information about all mechanistic parameters of interest. When Bayesian methods are applied to a nonidentifiable model, the subjective prior effectively fabricates information about any parameters about which the data carry no objective information. Finally, structural nonidentifiability can lead to spurious models that fit data well but can yield severely flawed inferences and predictions when they are interpreted or used inappropriately.     

A Simple Toxicokinetic Model Exhibiting Complex Dynamics and Nonlinear Exposure Response

Uncertainty in model predictions of exposure response at low exposures is a problem for risk assessment. A particular interest is the internal concentration of an agent in biological systems as a function of external exposure concentrations. Physiologically based pharmacokinetic (PBPK) models permit estimation of internal exposure concentrations in target tissues but most assume that model parameters are either fixed or instantaneously dose-dependent. Taking into account response times for biological regulatory mechanisms introduces new dynamic behaviors that have implications for low-dose exposure response in chronic exposure. A simple one-compartment simulation model is described in which internal concentrations summed over time exhibit significant nonlinearity and nonmonotonicity in relation to external concentrations due to delayed up- or downregulation of a metabolic pathway. These behaviors could be the mechanistic basis for homeostasis and for some apparent hormetic effects.     

An approach to stochastic programming for medium term planning

A number of methods of obtaining the distribution of the optimum of the ‘wait and see’ stochastic programming model have been proposed, but computational experience for these is currently limited to the solution of small problems. The purpose of this paper is to discuss the role of the ‘wait and see’ model in planning, and to propose a method of analysis based on the minimax and maximax decision criteria. The approach requires the solution of a special class of non-linear programming problems. Computational results to date suggest that it will be possible to analyse practically sized problems in this way.     

Quality of Life Indexes for National Policy: Review and Agenda for Research

A number of governments and public policy institutes have developed Quality of Life Indexes – statistics that attempt to measure the quality of life for entire states or regions. We develop 14 criteria for determining the validity and usefulness of such QOL indexes to public policy. We then review 22 of the most-used QOL indexes from around the world. We conclude that many of the indexes are successful in that they are reliable, have established time series measures, and can be disaggregated to study subpopulations. However, many fall short in four areas: (1) indexes vary greatly in their coverage and definitions of domains of QOL, (2) none of the indexes distinguish among the concepts of input, throughput, and output that are used by public policy analysts, (3) they fail to show how QOL outputs are sensitive to public policy inputs, and (4) none have examined convergent validity against each other. We conclude that many of these indexes are potentially very useful for public policy and recommend research to further improve them.     

Attitudinal acceptance of intimate partner violence among U.S. adults

Attitudinal acceptance of intimate partner violence (IPV) is an important correlate of violent behavior. This study examined acceptance of IPV using data collected from a nationally representative telephone survey of 5,238 adults. Multivariable logistic regression analyses were used to test for associations between sociodemographic characteristics, exposure to violence, question order, and acceptance of hitting a spouse or boyfriend/girlfriend under specific circumstances. Depending on the circumstance examined, acceptance of IPV was significantly higher among participants who were male and younger than 35; were non-White; were divorced, separated, or had never married; had not completed high school; had a low household income; or were victims of violence within the past 12 months. Participants were more accepting of women hitting men; they also were consistently more likely to report tolerance of IPV if they were asked first about women hitting men rather than men hitting women. Reports of IPV tolerance need to be interpreted within the context of the survey. Efforts to change IPV attitudes can be tailored to specific IPV circumstances and subgroups, and these efforts should emphasize that the use of physical violence is unacceptable to both genders.     

Racial identity, racial discrimination, perceived stress, and psychological distress among African American young adults

This study examines the direct and indirect relationships among racial identity, racial discrimination, perceived stress, and psychological distress in a sample of 555 African American young adults. A prospective study design was used to assess the influence of two dimensions of racial identity attitudes (i.e., centrality and public regard) on other study variables to investigate the relationship between racial identity attitudes and psychological distress. The results show some evidence of a direct relationship between racial centrality and psychological distress, as well as evidence of indirect relationships for both centrality and public regard through the impact of racial discrimination and perceived stress. In addition, racial centrality was both a risk factor for experiencing discrimination and a protective factor in buffering the negative impact of discrimination on psychological distress. Results are discussed within the context of identifying multiple pathways to psychological well-being for African American young adults within the context of racial discrimination.     

"He is everything": religion's role in the lives of immigrant youth

Using emergent theme analysis of qualitative interview data in combination with quantitative survey data, the role of religion in the lives of immigrant youth was explored. Latino, Haitian, and Chinese teenagers described, in their own rich words, the significance of religion to them; their responses are reflected in themes that point to the potential protective role of religion for some immigrant groups.