A comparative analysis of North American adolescent and adult mass murderers

Thirty adult mass murderers and 34 adolescent mass murderers in North America are compared on both offender and offense variables to delineate similarities and differences. Findings indicate a plethora of psychiatric disturbances and odd/reclusive and acting-out personality traits. Predisposing factors include a fascination with weapons and war among many of the adolescents and the development of a "warrior mentality" in most of the adults. Precipitating factors indicate a major rejection or loss in the hours or days preceding the mass murder. Results are interpreted through the lens of threat assessment for targeted violence (Borum, Fein, Vossekuil, & Bergland 1999), recognizing that a fact-based, dynamic behavioral approach is most useful for mitigating risk of such an extremely low-base-rate violent crime.     

Pigeons encode absolute distance but relational direction from landmarks and walls

In recent studies, researchers have examined animals' use of absolute or relational distances in finding a hidden goal. When trained with an array of landmarks, most animals use the default strategy of searching at an absolute distance from 1 or more landmarks. In contrast, when trained in enclosures, animals often use the relationship among walls. In the present study, pigeons were trained to find the center of an array of landmarks or a set of short walls that did not block external cues. Expansion tests showed that both groups of pigeons primarily used an absolute distance strategy. However, on rotational tests, pigeons continued to search in the center of the array, suggesting that direction was learned in relation to array.     

Genetic basis for male aggression and survivorship in wild house mice (Mus domesticus)

Work on the genetic region of the house mice known as the t-complex has produced the hypothesis that mice heterozygous for t-haplotypes (+/t) may have a selective advantage over wild-type (+/+) males owing to the greater aggressiveness of +/t males. We tested this hypothesis by examining the behavior of +/+ and +/t mice placed in four large outdoor enclosures. We found that +/t males were dominant over +/+ males. Furthermore, in the outdoor enclosures +/t males had higher survivorship than +/+ males, both as adults and juveniles. However, males of the two genotypes did not differ in home range size. We suggest that t-haplotypes may be, in part, maintained in mouse populations because of a selective advantage in heterozygous males. © 1996 Wiley-Liss, Inc.     

Do Coping Styles Differ Across Sociocultural Groups? The Role of Measurement Equivalence in Making This Judgment

Cross-sociocultural group measurement equivalency is an important issue that generally has not been studied in the coping literature. Measurement equivalency of the COPE (Carver, Scheier, & Weintraub, 1989) was assessed across two sociocultural groups, a sample of 100 Anglo middle-class divorced mothers and a sample of 122 low-income Mexican American/Mexican immigrant mothers. A series of restrictive confirmatory factor analyses revealed that seven of the COPE's subscales may be measuring the same underlying construct across populations. However, scores derived from the subscales may not represent the same magnitude of the construct in these two groups. This study makes an important first step in furthering the understanding of coping strategies in low-income Mexican American/Mexican immigrant mothers. This study also illustrates the importance of testing for measurement equivalency before conducting comparative research in disparate populations.     

THE USE OF BEHAVIORAL ASSESSMENT TO PRESCRIBE AND EVALUATE TREATMENTS FOR SEVERELY HANDICAPPED CHILDREN

Behavioral assessment procedures were used to prescribe and evaluate treatments of maladaptive behavior for 2 children with severe multiple handicaps. In Experiment 1, the results of an assessment of reinforcer preference were used in conjunction with a functional analysis of the conditions maintaining self-injurious behavior to prescribe a treatment for a child with severe disabilities. The treatment procedure involved the use of a pressure-sensitive microswitch to activate reinforcing stimuli during two solitary conditions, during which self-injurious behavior had occurred at high rates. The results were evaluated with a multiple baseline across settings design and indicated that self-injury decreased with concomitant increases in microswitch activation. Results were maintained at 6 weeks, 8 weeks, and 6 months. In Experiment 2, the results of behavioral assessments of reinforcer preference and self-injurious behavior were combined to develop a treatment for a second severely handicapped child, who exhibited high rates of self-injury in demand situations. This treatment was evaluated with a multiple baseline across tasks design and resulted in the elimination of self-injury for up to 15 months.     

A Comparison of Latent Inhibition and Learned Irrelevance Pre-Exposure Effects in Rabbit and Human Eyeblink Conditioning

The learning of an association between a CS and a US can be retarded by unreinforced presentations of the CS alone (termed latent inhibition or LI) or by un-correlated presentations of the CS and US (termed learned irrelevance or LIRR). In rabbit eyeblink conditioning, there have been some recent failures to replicate LI. LIRR has been hypothesized as producing a stronger retardation effect than LI based on both empirical studies and computational models. In the work presented here, we examined the relative strength of LI and LIRR in eyeblink conditioning in rabbits and humans. In both species, a number of preexposure trials sufficient to produce LIRR failed to produce LI (Experiments 1 & 3). Doubling the number of CS pre-exposures did produce LI in rabbits (Experiment 2), but not in humans (Experiment 4). LI was demonstrated in humans only after manipulations including an increased inter-trial interval or ITI (Experiment 5). Overall, it appears that LIRR is a more easily producible pre-exposure retardation effect than LI for eyeblink conditioning in both rabbits and humans. Several theoretical mechanisms for LI including the conditioned attention theory, stimulus compression, novelty, and the switching theory are discussed as possible explanations for the differences between LIRR and LI. Overall, future work involving testing the neural substrates of pre-exposure effects may benefit from the use of LIRR rather than LI.     

Active school travel is associated with fewer suicide attempts among adolescents from low-and middle-income countries

Background/Objective: This study explored the association between active school travel (AST) and suicide attempts among adolescents in low- and middle-income countries (LMICs). Method: We used the data from the Global School-based Health Survey, including 127,097 adolescents aged 13-17 years from 34 LMICs. A self-reported survey was used to collect data on AST and suicide attempts as well as some variables. Multivariable logistic regression was performed to assess the association between AST and suicide attempts. A meta-analysis with random effects was undertaken to identify the difference in the association between AST and suicide attempts. Results: Across all the adolescents, the prevalence of AST was 37% and the prevalence of suicide attempts was 11.60%. Adolescents who engaged in AST were less likely to have suicide attempts irrespective of gender. The country-wise analysis indicated a large inconsistency in the association between AST and suicide attempt across the countries. Conclusions: AST would appear to be a protective factor for reducing suicide attempts among adolescents. However, the association between AST and suicide attempts varied greatly across the countries. Future studies should confirm the association between AST and suicide attempts.