Understanding Interaction Models: Improving Empirical Analyses

William Roberts Clark University of Michigan, Center for Political Studies, ISR 4202 Box 1248, 426 Thompson Street, Ann Arbor, MI 48106-1248 Matt Golder Florida State University, Department of Political Science, 531 Bellamy Building, Tallahassee, FL 32306-2230 e-mail: thomas.brambor{at}nyu.edu e-mail: wrclark{at}umich.edu e-mail: matt.golder{at}nyu.edu (corresponding author) Multiplicative interaction models are common in the quantitativepolitical science literature. This is so for good reason. Institutionalarguments frequently imply that the relationship between politicalinputs and outcomes varies depending on the institutional context.Models of strategic interaction typically produce conditionalhypotheses as well. Although conditional hypotheses are ubiquitousin political science and multiplicative interaction models havebeen found to capture their intuition quite well, a survey ofthe top three political science journals from 1998 to 2002 suggeststhat the execution of these models is often flawed and inferentialerrors are common. We believe that considerable progress inour understanding of the political world can occur if scholarsfollow the simple checklist of dos and don'ts for using multiplicativeinteraction models presented in this article. Only 10% of thearticles in our survey followed the checklist.     

Three species of insects collected from an adult human corpse above 3300 m in elevation: a review of a case from Colorado

We report on the colonization of an adult human corpse by three insect species at 3350 m (11,000 ft) in elevation. The adult silphid Thanatophilus coloradensis (Wickham), adults of the blow fly Calliphora coloradensis (Hough), and larvae and adults of Lucilia silvarum (Meigen) were all collected from the victim's body which had been wrapped in plastic. The victim was found in late June in the Rocky Mountains of Colorado. This paper provides additional confirmation of the taxa utilizing a human corpse at high elevations in Colorado.     

Visual attention and expertise for forensic signature analysis

Eye tracking was used to measure visual attention of nine forensic document examiners (FDEs) and 12 control subjects on a blind signature comparison trial. Subjects evaluated 32 questioned signatures (16 genuine, eight disguised, and eight forged) which were compared, on screen, with four known signatures of the specimen provider while their eye movements, response times, and opinions were recorded. FDEs' opinions were significantly more accurate than controls, providing further evidence of FDE expertise. Both control and FDE subjects looked at signature features in a very similar way and the difference in the accuracy of their opinions can be accounted for by different cognitive processing of the visual information that they extract from the images. In a separate experiment the FDEs re-examined a reordered set of the same 32 questioned signatures. In this phase each signature was presented for only 100 msec to test if eye movements are relevant in forming opinions; performance significantly dropped, but not to chance levels indicating that the examination process comprises a combination of both global and local feature extraction strategies.     

Suicide with associated acts of arson: two cases from Colorado

We report on two cases of suicide in which the victims started fires before their deaths. In one case the victim died of a single self-inflicted gunshot wound to the head after setting several fires in his residence. In the second case the victim hung himself after setting several fires in his residence and an adjoining building. In both cases, the victim's position was not near the origin of the fires suggesting that the arson was not a failsafe device to the primary mechanism of suicide. Neither victim showed a significant percentage of carboxyhemoglobin, or thermal damage from the fires. Both cases are remarkable in that, had the fire caused more damage to the remains and dwellings, a finding of suicide may not have been reached. We discuss similar aspects between the two reported cases and discuss differences observed with similar events such as complex suicide, suicide by self-immolation, and concealed homicide by burning. Similar cases should be reported to broaden our understanding of these complex events.     

Group Differences in Fairness Perceptions and Decision Making in Voting Rights Cases

Participants recruited from one Historically Black University (HBU) and two predominantly White higher-education institutions evaluated and decided simulated voting rights case summaries in which the plaintiff was either a racially-defined (African American) or a nonracially-defined (farmers) minority group. Contrary to social identity and social justice findings of an in-group bias, the present study showed greater support at all institutions for the voting rights of the African Americans than for the rural farmers, and the greatest support for both minority groups was found at the HBU. Perceived evidence strength was a better predictor of decisions than perceived unfairness, and both of these predictor variables completely mediated the effects of institution-type and involvement of a racially-defined group on decisions.     

The use of mitochondrial cytochrome oxidase I gene (COI) to differentiate two UK blowfly species -- Calliphora vicina and Calliphora vomitoria

Traditionally identification of forensically important insects has been carried out based upon morphological differences between species. However insect evidence found at a crime scene may on occasion be difficult to distinguish by morphological techniques and under these circumstances another method of accurate identification is required. This work utilises a cytochrome oxidase I partial mitochondrial gene region (COI) to distinguish the two of the main UK blowfly species -- Calliphora vicina (Robineau Desvoidy) and Calliphora vomitoria (Linnaeus) (Diptera:Calliphoridae). Seventeen interspecific differences in COI sequence were located. Use of the restriction enzyme SfcI on this gene region provides a simple method for distinguishing between C. vicina and C. vomitoria.     

Role of chemical tests and scene investigation in determination of range of fire

Forensic pathologists have historically found several characteristics of the entrance wound invaluable in determining range of fire in gunshot fatalities. Among these characteristics are the pattern and constituents of any deposited material such as soot and/or gun powder residues. We describe a case in which the application of previously described characteristics, in the absence of laboratory testing and examination of the crime scene, would have led to an erroneous conclusion with potentially grave consequences. We suggest that all attempts be made to use available laboratory tests and to perform detailed examination of crime scenes in determining the circumstances surrounding fatal gunshot injuries.     

Two-Year Reliability of the Propensity for Abusiveness Scale

The Propensity for Abusiveness Scale (PAS; Dutton [1995a] J. Fam. Violence 10[2]: 203–221) has been shown to correlate with both physical and psychological abuse in a variety of samples including gay men, assaultive males, and male and female college students (Clift, 2001; Dutton et al., 2001). For the current study, 27 male and 37 female university students completed the PAS during the 1998–1999 and the 2000–2001 school years. A 2-year test–retest reliability coefficient of r = .851 was found for women and a reliability coefficient of r = .629 was found for men. The combined sample had a reliability coefficient of r = .774. Moderate test–retest reliability coefficients were also found for each of the subscales.