Cluster analysis in community research: Epistemology and practice

Cluster analysis refers to a family of methods for identifying cases with distinctive characteristics in heterogeneous samples and combining them into homogeneous groups. This approach provides a great deal of information about the types of cases and the distributions of variables in a sample. This paper considers cluster analysis as a quantitative complement to the traditional linear statistics that often characterize community psychology research. Cluster analysis emphasizes diversity rather than central tendency. This makes it a valuable tool for a wide range of familiar problems in community research. A number of these applications are considered here, including the assessment of change over time, network composition, network density, person-setting relationships, and community diversity. A User's Guide section is included, which outlines the major decisions involved in a basic cluster analyses. Despite difficulties associated with the identification of optimal cluster solutions, carefully planned, theoretically informed application of cluster analysis has much to offer community researchers. Editor's note: Dr. Edward Seidman served as action editor for this article while serving as Associate Editor for Methodology.     

In Defense of the Responsibility to Protect

This essay responds to Esther Reed's recent critique of the Responsibility to Protect (R2P) principle in this journal. It argues that Reed fundamentally misunderstands and misrepresents R2P. Her critique of R2P would have served well as a critique of the earlier concept of humanitarian intervention had it been penned in the late 1990s. But most of the problems and dangers that Reed identifies are in reality the very problems and dangers that R2P seeks to overcome, and I suggest that it does overcome them quite successfully. R2P does not impose Western ideals on the rest of the world, weaken the legal restrictions on the use of force, or promote abusive interventionism. Rather, it offers a bold but carefully constructed framework that holds the promise of promoting the protection of vulnerable populations from mass atrocities.     

Double standards: Memory loading in temporal reference memory

Three experiments compared human performance on temporal generalization tasks with either one or two different, and distinct, standard durations encoded. In the first two experiments participants received presentations of two different standards at the beginning of each trial block and were instructed to encode either one or both of them. When instructed to encode one standard they then had to judge whether each of a number of comparison stimuli was or was not that standard. When instructed to encode both they were then tested using just one of the standards but the participants were unaware, at the time of encoding, which standard would later be used as a reference. No marked effect of the number of temporal standards encoded was found. In Experiment 3 participants received either one or two temporal standards and had to use both when two were presented. This manipulation produced flatter generalization gradients when two standards were encoded than when just one was, and modelling attributed this difference mainly to an increase in reference memory variability in the double-standard case. This suggests that the variability of representation of durations in temporal reference memory can be systematically increased by increasing temporal reference memory load.     

Subjective judgements of synergistic risks: a cognitive reasoning perspective

Mounting evidence that certain hazard combinations present synergistic risks for adverse outcomes, including violent crime, cancer, and species extinction, highlights the importance of understanding the risk attributable to combined hazards. However, previous studies indicate that individuals often misjudge synergistic risks as additive or sub-additive risks, and there is little research that explores the cognitive reasoning that may lead individuals to make such judgements. This study aims to fill this gap. Participants were asked to review several scenarios that described the risk magnitude presented by a combined hazard. They were required to judge whether each scenario was possible and to explain the reasoning that led to their judgement. The results show that many participants demonstrated an awareness of synergistic risk and that their reasoning was typically characterized by rudimentary knowledge of an underlying causal mechanism for the increased risk (e.g., a chemical reaction between drugs). Conversely, several participants adopted a line of reasoning that precluded the concept of synergistic risk. Many of these participants appeared to employ an additive model of risk, corresponding to the notion of 'adding' one hazard to another. Contrary to much previous research, we found little evidence to indicate that people tend to employ a sub-additive model of risk for combined hazards. Implications for future research and the improvement of risk communications concerning synergistic risks are discussed.