Separability of item and person parameters in response time models

This paper discusses two forms of separability of item and person parameters in the context of response time (RT) models. The first is separate sufficiency: the existence of sufficient statistics for the item (person) parameters that do not depend on the person (item) parameters. The second is ranking independence: the likelihood of the item (person) ranking with respect to RTs does not depend on the person (item) parameters. For each form a theorem stating sufficient conditions, is proved. The two forms of separability are shown to include several (special cases of) models from psychometric and biometric literature. Ranking independence imposes no restrictions on the general distribution form, but on its parametrization. An estimation procedure based upon ranks and pseudolikelihood theory is discussed, as well as the relation of ranking independence to the concept of double monotonicity.I am indebted to Wim van der Linden for bringing Thissen's (1983) paper to my notice, and to Martijn Berger, Frans Tan, and the anonymous reviewers for their constructive comments on earlier drafts of this paper.     

How Long Do Offenders Escape Arrest? Using DNA Traces to Analyse when Serial Offenders Are Caught

Why is it that some serial offenders are arrested quickly and others only after a long period, or never at all? What characterises offenders who continue to escape arrest despite their continued involvement in crime? To be able to answer these questions, arrested (identified) offenders must be compared with never arrested (unidentified) offenders. In this paper, data from the Dutch DNA database are used to assess which characteristics of the criminal behaviour of unidentified offenders influence the probability that they will subsequently be arrested. DNA data offer a unique opportunity to compare crime series of identified offenders with crime series of yet unidentified offenders. Using the Cox proportional hazards model, we tested whether the number of crimes committed, offence specialization, and offence seriousness affect the probability of arrest of serial offenders. Results showed that as an offender commits more crimes, the probability that he will be arrested increases and that offence specialization decreases the probability of arrest. Another conclusion drawn is that DNA traces offer unique opportunities for criminological research. We discuss the limitations of this new data source and make suggestions for future research using DNA traces and for future research that might improve the current study. Copyright © 2012 John Wiley & Sons, Ltd.     

Evaluating the influence of approaching vehicles on pedestrian’s visual patterns and crossing behaviors at an uncontrolled crosswalk

The visual behaviors and movement characteristics of pedestrians are related to their surrounding potential safety hazards, such as approaching vehicles. This study primarily aimed to investigate the visual patterns and walking behaviors of pedestrians interacting with approaching vehicles. Field experiments were conducted at two uncontrolled crosswalks located at the Cuihua and Yanta roads in Xi’an, China. The visual performance of pedestrians was assessed using the eye tracking system from SensoMotoric Instruments (SMI). Moreover, motion trajectories of the pedestrians and approaching vehicles were obtained using an unmanned aerial vehicle. Subsequently, the visual attributes and movement trajectories of pedestrians and motion trajectories of approaching vehicles were statistically analyzed. The results showed that approaching vehicles distracted the fixation of crossing pedestrians significantly, and occupied 29.5% of the total duration of fixation; that is, pedestrians always directed more fixation points to the approaching vehicles compared to other stimuli. As a vehicle approached, pedestrians’ fixation shifted from other areas of interest to the vehicle. Moreover, an increase in the velocity of the vehicle and a closer distance between pedestrian and the vehicle resulted in an increase in the pedestrians’ duration of fixation on the approaching vehicle, and they implemented more saccades. Furthermore, approaching vehicle’s velocity and distance between pedestrian and approaching vehicle are not significantly associated with pedestrian’s movement attributes. These findings provide insights into the crossing behavior of pedestrians during pedestrian-vehicle interactions, which could assist future researchers and policy makers.     

Environmental anxiety: Assessing emotional distress and concerns after toxin exposure

Abstract

Anxiety in face of environmental risks is common, but few attempts have been made to assess individual differences psychometrically and to validate the measures in samples that have suffered from exposure to neurotoxic substances. The present study deals with this problem in two ways. First, levels of general anxiety were determined in two large independent samples of workers who were exposed to multiple organic solvents and in their nonexposed referents. In both samples, anxiety was substantially higher in exposed subjects than in their referents. Second, an Environmental Worry Scale (EWS) was developed and validated in three samples. This 17-item instrument and its 8-item subscale yielded satisfactory psychometric properties and also succeeded in discriminating solvent exposed from nonexposed subjects. Finally, the EWS was used in a structural equation model that was designed to predict the intention to avoid chemicals. The worry factor served as a mediator between exposure and intention, whereas exposure by itself did not influence intentions.     

Preventing childhood accidents in the home: Parental behavior to reduce household hazards

The parents of all children between 6 and 18 months in four Norwegian municipalities participated in an investigation to assess to what extent parents take actions to reduce household hazards their children are exposed to, and to identify factors associated with such behaviors. The Health Belief Model was used as a theoretical framework guiding the selection of variables. The results indicate that most parents take considerable action to reduce household hazards. The constructs derived from the Health Belief Model accounted for only a small part of the variance in parental behavior to reduce hazards in the home.     

Bonding and bridging social capital and their associations with self‐evaluated community resilience: A comparative study of East Asia

The purpose of this study is to test key social capital indicators in a disaster context by considering the bonding and bridging types of social capital. Using the East Asian Social Survey, this study chooses three behavioural/cognitive elements of social capital—social trust, voluntary association membership, and personal networks—and divides them into bonding and bridging social capital, in‐group and out‐group trust, homogeneous and heterogeneous membership, and strong and weak ties to test their effects on self‐evaluated community resilience to natural hazards. The results showed that social trust and personal networks had strong positive effects, but the effect of voluntary association membership was positive in societies with high rates of membership (Japan and South Korea) and negative in a society with a low rate of membership (Taiwan). Furthermore, while bonding social capital generally showed a stronger effect than bridging social capital in East Asia, a society with more frequent and intense disasters (Japan) showed a strong effect of heterogenous membership on self‐evaluated community resilience. This study connects two aspects of social capital studies—the elements and the types of social capital—and the findings imply that the relationship between social capital and community resilience may have some mediator variables.     

An accumulator model for responses and response times in tests based on the proportional hazards model

Latent trait models for responses and response times in tests often lack a substantial interpretation in terms of a cognitive process model. This is a drawback because process models are helpful in clarifying the meaning of the latent traits. In the present paper, a new model for responses and response times in tests is presented. The model is based on the proportional hazards model for competing risks. Two processes are assumed, one reflecting the increase in knowledge and the second the tendency to discontinue. The processes can be characterized by two proportional hazards models whose baseline hazard functions correspond to the temporary increase in knowledge and discouragement. The model can be calibrated with marginal maximum likelihood estimation and an application of the ECM algorithm. Two tests of model fit are proposed. The amenability of the proposed approaches to model calibration and model evaluation is demonstrated in a simulation study. Finally, the model is used for the analysis of two empirical data sets.     

Semi‐parametric proportional hazards models with crossed random effects for psychometric response times

The semi‐parametric proportional hazards model with crossed random effects has two important characteristics: it avoids explicit specification of the response time distribution by using semi‐parametric models, and it captures heterogeneity that is due to subjects and items. The proposed model has a proportionality parameter for the speed of each test taker, for the time intensity of each item, and for subject or item characteristics of interest. It is shown how all these parameters can be estimated by Markov chain Monte Carlo methods (Gibbs sampling). The performance of the estimation procedure is assessed with simulations and the model is further illustrated with the analysis of response times from a visual recognition task.     

State Hospital Reentry Among Youth with Serious Emotional Disturbance: A Longitudinal Analysis

We investigated the demographic, service history, and clinical factors associated with readmission to state operated inpatient psychiatric hospitals by children and adolescents. Using computerized administrative data records for 3,969 consecutive index admissions of individuals between the ages of 7 and 17 inclusive, we examined hospital reentry among youth receiving services at these facilities. The univariate analysis comparing youths who reentered the hospital with those who did not reenter indicated that reentry was more likely to occur among African American youths and among those who were diagnosed with psychotic disorders. Reentry occurred less frequently among youths diagnosed with depressive disorders. Reentry also occurred less frequently among youths living in areas having an organized array of community-based mental health services. Youths who reentered the hospital were significantly older and had longer prior hospitalizations than those not reentering. The proportional hazards model used in the analysis indicated several factors associated with increased likelihood of hospital reentry. African American youths and individuals diagnosed with a psychotic disorder were more likely to reenter the hospital. Younger youths and those having lengthy prior hospitalizations were at increased risk for reentering the hospital. Youths living in urban, white, higher income communities were less likely to reenter the hospital.