Personality as a moderator of context effects on academic achievement

We investigated whether personality moderates group influence of classmates on academic achievement and whether these so-called context effects can be attributed to peer pressure. The sample consisted of 2498 students in their first year of Dutch secondary education. The data were analyzed by a two-level (students within classes) analysis, separately for boys (n = 1033, in 92 classes) and girls (n = 1465, in 119 classes). For both sexes, we found a context effect on Dutch language achievement but not on mathematics achievement. Emotional Stability appeared a moderator of this context effect but for girls only. The results suggest further that peer pressure is not a likely mechanism of group influence of classmates on academic achievement.     

Parental Influences on the Prevalence and Development of Child Aggressiveness

The development of aggressiveness between 5 and 17 years and some parental influences on this development were analyzed using data from Germany. International studies have shown a “camel humps” curve, i.e., a peak of aggression of children (primarily boys) between 2 and 4 years and a second peak of antisocial or aggressive behavior of boys between 15 and 20 years, but small groups of children and adolescents were persistently aggressive. A representative longitudinal study (2,190 children and their parents) and an additional study (1,372 children and adolescents) were conducted in Germany. The hypotheses of this article are that in the data can be found (a) an U-shaped course of aggressiveness for boys and girls, but on different levels, (b) a minority of persistently aggressive children and youth, (c) influences of parental temperaments, behavioral tendencies, parenting styles and the family status on the children’s aggressiveness. The results replicate roughly the “valley” of the U-shaped course of aggressiveness. Small groups of chronically aggressive children were found as well. Influences of parental temperaments and corresponding behavioral tendencies (internalizing and externalizing behavior), parenting styles (child-centered communication, use of violence) and the social status of the families on child aggressiveness confirmed the hypotheses. These processes were moderated by gender effects between mothers, fathers, daughters, and sons. In regard to the group of persistently aggressive young people prevention of aggression should start early in childhood and over the long term. Parent education should consider more the individual personalities of the parents, not only parenting styles.     

Affective norms for 380 Spanish words belonging to three different semantic categories

Emotional words are increasingly used in the study of word processing. To elucidate whether the experimental effects obtained with these words are due either to their affective content or to other semantic characteristics, it is necessary to conduct experiments with affectively valenced words obtained from different semantic categories. In the present article, we present affective ratings for 380 Spanish words belonging to three semantic categories: animals, people, and objects. The norms are based on the assessments made by 504 participants, who rated about 47 words either in valence and arousal, by using the Self-Assessment Manikin (Bradley & Lang, Journal of Behavioral Therapy and Experimental Psychiatry, 25, 49-59. 1994), or in concreteness and familiarity. These ratings will help researchers select stimuli for experiments in which both the affective properties of words and their membership to a given semantic category have to be taken into account. The database is available as an online supplement for this article.     

Self- and social perception of physical appearance in chest wall deformity

This study analyzes self- and social perception of physical appearance in patients with chest wall deformity (CWD), including both pectus carinatum and pectus excavatum. Self-perception of appearance in 76 patients with CWD and social perception of patients' appearance by 20 adult and 20 adolescent raters was assessed using the Appearance Rating Scale (Stangier et al., 2000) and evaluated for agreement and multivariate correlates. Results indicate no agreement between self- and social rating. Based on mean scores patients rated their appearance significantly more negatively than adult raters but only slightly different than adolescent raters. Adolescent raters' judgment of the patients' appearance was related to CWD characteristics, while self-rating rather seems to be related to psychosocial factors. Because adolescents are a relevant peer group for adolescent patients with CWD their evaluation of the appearance might influence patients' self-image and might affect their psychological functioning. Effective interventions focusing on social interactions are needed.     

Water temperature determines neurochemical and behavioural responses to forced swim stress: an in vivo microdialysis and biotelemetry study in rats

Forced swimming is a behavioural stress model increasingly used to investigate the neurocircuitry of stress responses. Although forced swim stress clearly is a psychological stressor (anxiety, panic), its physical aspects are often neglected. There are indications that behavioural and neurochemical responses to swim stress depend on the water temperature. Thus, we investigated the responsiveness of hippocampal serotonergic neurotransmission (important in the coordination of stress responses), and of behaviour and core body temperature to forced swimming at different water temperatures (19, 25 and 35 degrees C). In vivo microdialysis and biotelemetry in freely-behaving rats were used. Dialysates were analysed for serotonin (5-HT) and its metabolite 5-HIAA (5-hydroxyindoleacetic acid) by HPLC with electrochemical detection. Forced swimming in water at 25 and 19 degrees C decreased core body temperature by 8 and 12 degrees C, respectively. A rapid and pronounced increase in hippocampal 5-HT and 5-HIAA was found in rats that swam at 35 degrees C, whereas biphasic responses in 5-HT and 5-HIAA were observed at 25 and 19 degrees C. Also swim stress behaviour and post-stress home cage behaviour depended on the water temperature. Comparing the serotonergic and core body temperature changes revealed that a combination of two different 5-HT and 5-HIAA responses seems to shape the neurotransmitter response. Swimming-induced increases in hippocampal extracellular concentrations of 5-HT and 5-HIAA occurred at all water temperatures, but these increases were temporarily quenched, or concentrations were transistently decreased, when core body temperature fell below 31 degrees C in water at 25 or 19 degrees C. These data demonstrate that water temperature is a key factor determining the impact of forced swim stress on behaviour and neurochemistry, and underscore that changes in these parameters should be interpreted in the light of the autonomic responses induced by this stressor.     

Social comparison with friends versus non‐friends

This paper investigates whether several aspects of social comparison in school classes differ as a function of the type of relation between the student and his or her target. Participants were 9612 students in the first grade of secondary education in the Netherlands (equivalent to Grade 7 in the US). Results indicated that (1) 78% of the students who had at least one friend also compared with a friend; (2) social comparison with friends was much more often reciprocal than comparison with non‐friends; (3) preferences for upward and downward comparison were less often given by students who compared with friends than students who compared with non‐friends; (4) the similarity in initial performance level between students and their comparison targets was higher when targets were friends; (5) despite these differences, which seem to imply that friends often serve as routine standards whereas non‐friends are more deliberately chosen as comparison targets, it appeared that consequences of social comparison for subsequent performance were about the same for both types of relations. Further findings of this paper suggest that previously found effects of friends' grades on subsequent performance may be explained by social comparison. Copyright © 2007 John Wiley & Sons, Ltd.     

Great apes’ performance in discriminating weight and achromatic color

Much work has been done on visual discrimination in primates over the past decade. In contrast, very little is known about the relevance of non-visual information in discrimination learning. We investigated weight and achromatic color (color, henceforth) discrimination in bonobos, gorillas and orangutans, using the exchange paradigm in which subjects have to give objects to the experimenter in order to receive a reward. Unlike previous studies, subjects were not trained to lift objects because lifting the objects was an integral part of the exchange procedure. This methodology also allowed us a direct comparison between visual and weight discrimination. We presented 12 subjects (5 bonobos, 2 gorillas and 5 orangutans) with two sets of objects corresponding to two conditions. The objects in the color condition (white/black) differed only in color and those in the weight condition (light/heavy) differed only in weight. Five apes learned to discriminate weight and six to discriminate color. Subjects learned color discrimination faster than weight discrimination. Our results suggest that bonobos and orangutans are sensitive to differences in weight and able to learn discriminating objects that differ in this property.