Heterogeneous heterogeneity by default: Testing categorical moderators in mixed-effects meta-analysis

Categorical moderators are often included in mixed-effects meta-analysis to explain heterogeneity in effect sizes. An assumption in tests of categorical moderator effects is that of a constant between-study variance across all levels of the moderator. Although it rarely receives serious thought, there can be statistical ramifications to upholding this assumption. We propose that researchers should instead default to assuming unequal between-study variances when analysing categorical moderators. To achieve this, we suggest using a mixed-effects location-scale model (MELSM) to allow group-specific estimates for the between-study variance. In two extensive simulation studies, we show that in terms of Type I error and statistical power, little is lost by using the MELSM for moderator tests, but there can be serious costs when an equal variance mixed-effects model (MEM) is used. Most notably, in scenarios with balanced sample sizes or equal between-study variance, the Type I error and power rates are nearly identical between the MEM and the MELSM. On the other hand, with imbalanced sample sizes and unequal variances, the Type I error rate under the MEM can be grossly inflated or overly conservative, whereas the MELSM does comparatively well in controlling the Type I error across the majority of cases. A notable exception where the MELSM did not clearly outperform the MEM was in the case of few studies (e.g., 5). With respect to power, the MELSM had similar or higher power than the MEM in conditions where the latter produced non-inflated Type 1 error rates. Together, our results support the idea that assuming unequal between-study variances is preferred as a default strategy when testing categorical moderators.     

Interpersonal Psychotherapy—Adolescent Skills Training With Youth From Asian American and Immigrant Families: Cultural Considerations and Intervention Process

Although research has identified effective evidence-based depression prevention interventions for diverse youth, little is known about how the intervention process unfolds with immigrant family youth. This study utilized a qualitative approach to explore cultural and clinical differences in the implementation of Interpersonal Psychotherapy–Adolescent Skills Training (IPT-AST) in two schools, one serving youth from primarily immigrant, Asian American families and the second, youth from mostly nonimmigrant, non-Hispanic White families. A total of 131 IPT–AST sessions were audio recorded, transcribed, and coded for presence and patterns of cultural and clinical constructs. Results revealed that sessions with immigrant family youth were more likely to contain discussions of interpersonal problems characterized by estrangement, goals of spending time together with important others, mentions of emotion suppression and academic achievement expectations, conversations about acculturation, differences in value orientation, and discomfort with implementing new intervention skills. Dialogue from interventionist and youth exchanges is presented to illustrate how these themes emerged and were addressed by interventionists in a culturally responsive manner. The study highlights how IPT–AST with immigrant family and Asian American youth may unfold differently compared to youth from nonimmigrant families. Implications of findings for providers are discussed.     

Understanding of the concept of numerically "less" by bottlenose dolphins (Tursiops truncatus)

In 2 experiments, bottlenose dolphins (Tursiops truncatus) judged the ordinal relationship between novel numerosities. The dolphins were first trained to choose the exemplar with the fewer number of items when presented with just a few specific comparisons (e.g., 2 vs. 6, 1 vs. 3, and 3 vs. 7). Generalization of this rule was then tested by presenting the dolphins with all possible pairwise comparisons between 1 and 8. The dolphins chose the exemplar with the fewer number of items at levels far above chance, showing that they could recognize and represent numerosities on an ordinal scale. Their pattern of errors was consistent with the idea of an underlying analog magnitude representation.     

How do memory systems interact? Evidence from human classification learning

Studies of human classification learning using functional neuroimaging have suggested that basal ganglia and medial temporal lobe memory systems may interact during learning. We review these results and outline a set of possible mechanisms for such interactions. Effective connectivity analyses suggest that interaction between basal ganglia and medial temporal lobe are mediated by prefrontal cortex rather than by direct connectivity between regions. A review of possible neurobiological mechanisms suggests that interactions may be driven by neuromodulatory systems in addition to mediation by interaction of inputs to prefrontal cortical neurons. These results suggest that memory system interactions may reflect multiple mechanisms that combine to optimize behavior based on experience.     

Gender and culture differences in emotion

In this article, the authors report a secondary analysis on a cross-cultural dataset on gender differences in 6 emotions, collected in 37 countries all over the world. The aim was to test the universality of the gender-specific pattern found in studies with Western respondents, namely that men report more powerful emotions (e.g., anger), whereas women report more powerless emotions (e.g., sadness, fear). The authors expected the strength of these gender differences to depend on women's status and roles in their respective countries, as operationalized by the Gender Empowerment Measure (GEM; United Nations Development Programme Human Development Report 2002). Overall, the gender-specific pattern of women reporting to experience and express more powerless emotions and men more powerful emotions was replicated, and only some interactions with the GEM were found.     

Deficits of motor intention following parietal lesions

Patients with lesions to the right parietal lobe were tested on their ability to reach to targets, or to respond verbally to targets. The targets occurred at the same two spatial locations--to the left and right of the patient--with the task being cued by the color of the target. Patients were able to perform both tasks separately rapidly and without error. However, when the two tasks were interleaved, they had difficulty making a response in the left (contralesional) field when this was different to a response that they had just made. These results suggest that lesions to the parietal cortex may cause a deficit in the coding for motor intention, as well as attention in the contralesional field.     

Context-specificity of relapse: effects of therapist and environmental context on return of fear.

Context-specificity of fear extinction was tested among 65 participants who were fearful of spiders by manipulating the contexts used for exposure treatment and two-week follow-up assessment. Context was defined by both meaningful (presence of a particular therapist) and incidental (room location and furnishings) environmental cues. Distinct phobic stimuli were used to examine interactions of context with stimulus. Physiological, behavioral and verbal indices of fear were measured. Results provided modest support for context-specific return of fear. With one stimulus, participants assessed in a non-treatment context at follow-up exhibited greater returns in heart rate levels. In addition, three of four participants who could not touch the stimulus at follow-up had been tested in a non-treatment context. Future investigations may benefit from greater distinctions between contexts or manipulation of contextual features more directly relevant to fear. Finally, post hoc analyses identified high trait anxiety, slow treatment response, recovery of phobic cognitions and long duration/high intensity phobic encounters post-treatment as significant predictors of increased return of fear.     

Anxiety Symptomatology in Mexican-American Adolescents

Mexican-American adults and adolescents in general have been reported to have high levels of anxiety symptomatology. In our study of a tri-ethnic sample of 2528 junior and senior high school students, the Youth Self Report (YSR) version of the Child Behavior Checklist (CBCL) and a sociodemographic questionnaire was used to assess the anxiety symptoms of Hispanic youth. We compared the ratings on anxiety symptoms, using Achenbach's anxiety subscale on the YSR, between two populations. The anxiety levels of youth in coastal southeast Texas (Galveston County) were compared to the anxiety levels of youth in the lower Rio Grande Valley. We found that Mexican-Americans of the Lower Rio Grande Valley scored higher on anxiety symptoms than the tri-ethnic population of Galveston County. Other factors associated with higher anxiety scores for Mexican-American youths included being born outside the US, linguistic fluency, father absent from the home, mother's education, and household size. Multiple regression analyses showed that socio-economic status (SES), family composition, and linguistic fluency had a greater relative impact on anxiety symptomatology than all other factors, both for the total sample as well as for the Mexican-American sample. These results parallel previous findings, with Mexican-American adults, which suggest either higher risk for anxiety symptomatology or a culturally related bias in the reporting of such symptoms.