Markov Chain Monte Carlo in small worlds

As the number of applications for Markov Chain Monte Carlo (MCMC) grows, the power of these methods as well as their shortcomings become more apparent. While MCMC yields an almost automatic way to sample a space according to some distribution, its implementations often fall short of this task as they may lead to chains which converge too slowly or get trapped within one mode of a multi-modal space. Moreover, it may be difficult to determine if a chain is only sampling a certain area of the space or if it has indeed reached stationarity. In this paper, we show how a simple modification of the proposal mechanism results in faster convergence of the chain and helps to circumvent the problems described above. This mechanism, which is based on an idea from the field of “small-world” networks, amounts to adding occasional “wild” proposals to any local proposal scheme. We demonstrate through both theory and extensive simulations, that these new proposal distributions can greatly outperform the traditional local proposals when it comes to exploring complex heterogenous spaces and multi-modal distributions. Our method can easily be applied to most, if not all, problems involving MCMC and unlike many other remedies which improve the performance of MCMC it preserves the simplicity of the underlying algorithm.     

Aetiology of anorexia nervosa in Hong Kong: a social work qualitative inquiry

This paper reports the results of a qualitative inquiry into the aetiology of anorexia nervosa in Hong Kong. These results are part of our main research project about family treatment and families with a daughter suffering from anorexia nervosa. This present qualitative study adopts a multiple case study approach (n = 8) and employs a multiple‐source data collection method, involving pre‐ and post‐family treatment interviews, clinical observations of the participants during the treatment sessions and home visits, as well as detailed field notes. The findings indicate that there are biological, psychological, socio‐cultural and familial interpretations of the aetiology of anorexia nervosa. This study challenges the dominant discourse on anorexia nervosa in Hong Kong, which states that the root of the disease lies in a desire for slenderness and beauty, and suggests instead that the aetiology of anorexia nervosa can be discovered only if approached from the systems level. Implications for social work practice are highlighted.     

From child rescue to family protection: The evolution of the child protective movement in the United States

The child protective movement, an offshoot of animal protective work, initially adopted a punitive, law enforcement emphasis. Under the leadership of the Massachusetts Society for the Prevention of Cruelty to Children, anti-cruelty work took on a broader focus based on prevention rather than punishment. The new approach stressed the need to maintain and enrich family life through broad social supports, relying on family casework and social reform. “Normal family life,” a vaguely denned but firmly middle-class notion, was established as the ideal to which social agencies should subscribe in their drive to protect children and insure an orderly society. Child protection, formerly isolated from the child welfare movement, gradually became a part of it.     

The child and adolescent social perception measure

Tests currently available for measuring children's sensitivity to nonverbal aspects of communication have been criticized on methodological and conceptual grounds. The Child and Adolescent Social Perception Measure (CASP) was developed to meet the need for a clinically useful measure which examines social perception within a semi-naturalistic context. The CASP consists of 10 videotaped scenes, each of which lasts 19–40 seconds. The verbal content was removed through electronic filtering so that the ability to receive and interpret nonverbal social cues could be measured without bias from verbal cues. Children are shown the scenes and then questioned about the emotions portrayed. Based on standardization with 212 children and adolescents ages 6 to 15 years old, reliability (interrater, test-retest, internal consistency) and initial validity information are reported.Portions of this paper have been presented at the Congress of the World Federation of Occupational Therapists, London, England, 1994, and at the joint conference of the Canadian and American Occupational Therapists, Boston, 1994.We acknowledge funding from the Glenrose Rehabilitation Hospital Research Grants Program. We thank each of the actors and actresses who generously volunteered their time to produce the videotape; the students and teachers in the schools who participated in the collection of the normative data; and the research assistants who worked many hard hours to make this all possible (Janet L. Smith, Kara Ryan, Dixie McLean, Kate Murie, Taslim Pardhan).     

Conditions Facilitating Participatory-Democratic Organizations*

This paper examines “alternative institutions” in a variety of institutional domains as participatory-democratic modes of organizution. Grounded in comparative data, it posits structural conditions, both internal to an organization and in its environment, which support or undermine the achievement of its collectivist-democratic ideals. While the literature on social movement organizations well demonstrates the fragility of democratic systems and their tendency toward oligarchization, goal displacement, and organizational maintenance, this work suggests, in propositional form, conditions which militate against these all-too-common transformation patterns.