Model-based clustering with sparse covariance matrices

Statistics and Computing - Finite Gaussian mixture models are widely used for model-based clustering of continuous data. Nevertheless, since the number of model parameters scales quadratically with...     

Predicting Children's Prosocial and Co‐operative Behavior from Their Temperamental Profiles: A Person‐centered Approach

The goal of this study was to examine how aspects of self‐regulation and negative emotionality predicted children's co‐operative and prosocial behavior concurrently and longitudinally using the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development. Mothers completed measures of children's temperamental proneness to negative emotionality and self‐regulation at 54 months. Teachers and parents completed measures of children's co‐operative and prosocial behavior at 54 months, first grade, and third grade. A latent profile analysis of the temperamental variables revealed four profiles of children: those high in regulation and low in negative emotionality, those moderate in regulation and moderate in negative emotionality, those low in regulation and high in negative emotionality, and finally those who were very low in regulation but high in anger emotionality. Generally, children with profiles that were high or moderate in terms of regulation and low or moderate in terms of negative emotionality were rated as the most prosocial and co‐operative. Children with profiles that were less well regulated and who were high in negative emotionality (particularly anger proneness) were rated as less co‐operative and prosocial by parents and teachers.     

Demography of a ground nesting bird in an urban system: are populations self-sustaining?

Urbanization poses threats to earth’s biota, and retention of remnant native habitat in protected areas within expanding urban boundaries may help alleviate threats to wildlife. However, it is unclear for nearly all nonsynanthropic (i.e., not benefiting from an association with humans) species whether vital rates in urban habitats can sustain populations or if populations persist only through immigration from outside the urban boundary. We conducted a three-year study of spotted towhees (Aves: Pipilo maculatus) breeding in four undeveloped parks in Portland, OR, USA, to measure park-specific seasonal reproductive output (F) and annual adult survival (S_A). We developed a stochastic model that combined F and S_A with an estimate of first-year survival to measure population growth rate (λ) in all parks assumed to be closed to immigration. F differed among parks but S_A did not. Relatively high F was possible because many pairs raised >1 brood/season. When combined with empirical estimates of survival through the 30-day period of post-fledging parental care (S_D = 0.645), only 2 of 4 parks were self-sustaining (i.e., λ > 1.0). However, S_D reflected substantial loss of fledglings to domestic cats (Felis catus). Assuming no loss to cats and either partial compensatory or additive mortality of fledglings substantially improved prospects of population persistence for declining (sink) populations. Moreover, allowing low levels of immigration to sinks reversed population declines in most parks even when vital rates were insufficient to maintain populations. Our results suggest that nonsynanthropic bird species can persist in urban landscapes, but also that offspring mortality in the post-fledging period may be a critical determinant of population viability.     

A Dynamic Model of Demand for Houses and Neighborhoods

This paper develops a dynamic model of neighborhood choice along with a computationally light multi‐step estimator. The proposed empirical framework captures observed and unobserved preference heterogeneity across households and locations in a flexible way. We estimate the model using a newly assembled data set that matches demographic information from mortgage applications to the universe of housing transactions in the San Francisco Bay Area from 1994 to 2004. The results provide the first estimates of the marginal willingness to pay for several non‐marketed amenities—neighborhood air pollution, violent crime, and racial composition—in a dynamic framework. Comparing these estimates with those from a static version of the model highlights several important biases that arise when dynamic considerations are ignored.     

Women’s experiences of,and attitudes to,maternity education across the perinatal period in Victoria,Australia: A mixed-methods approach

Background

While the provision of maternity education across the perinatal period can increase the confidence and self-efficacy in childbearing women, there is still thought to be a lack of effective educational resources for parenthood. This study, conducted in Victoria, Australia, investigated women’s experiences of, and attitudes to education communicated in maternity service provision.

Mixture of latent trait analyzers for model-based clustering of categorical data

Model-based clustering methods for continuous data are well established and commonly used in a wide range of applications. However, model-based clustering methods for categorical data are less standard. Latent class analysis is a commonly used method for model-based clustering of binary data and/or categorical data, but due to an assumed local independence structure there may not be a correspondence between the estimated latent classes and groups in the population of interest. The mixture of latent trait analyzers model extends latent class analysis by assuming a model for the categorical response variables that depends on both a categorical latent class and a continuous latent trait variable; the discrete latent class accommodates group structure and the continuous latent trait accommodates dependence within these groups. Fitting the mixture of latent trait analyzers model is potentially difficult because the likelihood function involves an integral that cannot be evaluated analytically. We develop a variational approach for fitting the mixture of latent trait models and this provides an efficient model fitting strategy. The mixture of latent trait analyzers model is demonstrated on the analysis of data from the National Long Term Care Survey (NLTCS) and voting in the U.S. Congress. The model is shown to yield intuitive clustering results and it gives a much better fit than either latent class analysis or latent trait analysis alone.     

Charting the Emergence of National Identity in Children in Wales

This multimodal study, set in Wales, demonstrates that children aged nine and ten can clearly define and rationalise their own national identity. It contributes to age related discussions on how children categorise themselves in terms of national identity and the rationale for their choices. The children in the study used single and multiple definitions of national identity and illustrate the increasing plural nature of 21st century Wales. Family, birthplace and residency were identified as factors in shaping their national identity, more so than language, despite the current bilingual policy drive in Wales.     

The Caliban Codex: mud,blood and spurious issues

The internationally known and respected Cherokee Indian artist Jimmie Durham created the conceptual mixed-media installation The Caliban Codex in anticipation of the 1992 quincentennial Columbian celebrations that were held throughout the Americas. He used Shakespeare's The Tempest as a vehicle by which to critique colonialism's appropriation of language and its power to assert colonial authority. He also addressed physiognomy as it was employed during the nineteenth century in a pseudo-scientific endeavour to ‘prove’ the biological legitimacy of racism. In each case Durham employed the methods of mimicry and mockery to address the ambivalent relationship between the coloniser and the colonised as it continues to be experienced.