Competition between a Simultaneous and a Serial Feature in Appetitive Feature positive and Feature negative Discriminations

Two experiments with rats examined competition between simultaneous and serial features for behavioural control in an appetitive discrimination. In Experiment 1, an auditory target was reinforced when presented in isolation. For different groups, the target was non-reinforced when simultaneously accompanied by a visual feature (first group), when preceded by a serial visual feature (second group), or when both accompanied by a simultaneous feature and preceded by a serial feature (third group). Tests performed after discrimination learning revealed inhibitory control by the simultaneous feature in the first group and by the serial feature in the second group. In the third group, the simultaneous feature acquired inhibitory control over the target in isolation, whereas the serial feature did not. However, the serial feature further reduced responding to the target-simultaneous feature compound relative to responding shown to the compound in isolation. In Experiment 2, the same training procedure was used in three groups as in Experiment 1, except that the target was nonreinforced in isolation and reinforced in the presence of a simultaneous and/or serial feature. Tests revealed that the feature acquired excitatory control in the first and second groups. In the third group, both features acquired excitatory control, although the control exerted by the simultaneous feature was less strong than that observed in the group trained with only the simultaneous feature. The theoretical implications of these results regarding competition between occasion setters and Pavlovian excitors and inhibitors were discussed.     

Suicidal Ideation, Depression, and Conduct Disorder in a Sample of Adolescent and Young Adult Twins

The co-occurrence of suicidal ideation, depression, and conduct disturbance is likely explained in part by correlated genetic and environmental risk factors. Little is known about the specific nature of these associations. Structured interviews on 2,814 twins from the Virginia Twin Study of Adolescent Behavioral Development (VTSABD) and Young Adult Follow-Up (YAFU) yielded data on symptoms of depression, conduct disorder, and adolescent and young adult suicidal ideation. Univariate analyses revealed that the familial aggregation for each trait was explained by a combination of additive genetic and shared environmental effects. Suicidal ideation in adolescence was explained in part by genetic influences, but predominantly accounted for by environmental factors. A mixture of genetic and shared environmental influences explained ideation occurring in young adulthood. Multivariate analyses revealed that there are genetic and shared environmental effects common to suicidal ideation, depression, and conduct disorder. The association between adolescent suicidal ideation and CD was attributable to the same genetic and environmental risk factors for depression. These findings underscore that prevention and intervention strategies should reflect the different underlying mechanisms involving depression and conduct disorder to assist in identifying adolescents at suicidal risk.     

Gender Differences in Loneliness Across the Lifespan: A Meta‐Analysis

Different theoretical contentions on gender differences in loneliness exist, often including the emergence of gender differences in particular developmental periods. To explain those ideas, the current meta‐analysis synthesizes the available evidence on gender differences in loneliness across the lifespan. Three‐level meta‐analyses were conducted with 751 effect sizes, covering 399,798 individuals (45.56% males). Results showed a close‐to‐zero overall effect (g = 0.07). Most examined moderators were non‐significant, except for age, the scope of the sampling area, and year of publication. Most importantly, all effects were small, suggesting that across the lifespan mean levels of loneliness are similar for males and females.