Physical aggression and expressive vocabulary in 19-month-old twins

In the prevention of physical aggression, possible etiological links with language development are rarely taken into account. Indeed, little is known about when language and aggressive behavior become linked during development and which mechanisms are responsible for this association. This study investigated the association between physical aggression and language in late infancy with a genetic design that involved 562 19-month-old twins. A modest but significant correlation (r = -.20) was found between physical aggression and expressive vocabulary. Substantial heritability was found for physical aggression. Quantitative genetic modeling suggests that the correlation between expressive vocabulary and physical aggression cannot be explained by shared etiologies. However, phenotype-to-phenotype models indicate that the covariation can be entirely accounted for by a significant phenotypic path from expressive vocabulary to physical aggression. The implications of these results for early prevention of chronic physical aggression are discussed.     

Do Friends’ Characteristics Moderate the Prospective Links between Peer Victimization and Reactive and Proactive Aggression?

This study examined (a) the predictive link between peer victimization and children’s reactive and proactive aggression, and (b) the potential moderating effect of reciprocal friends’ reactive and proactive aggression in this context. The study also examined whether these potential moderating effects of friends’ characteristics were stronger with respect to more recent friends compared to previous friends. Based on a convenience sample of 658 twin children (326 boys and 332 girls) assessed in kindergarten and first grade, the results showed that peer victimization uniquely predicted an increase in children’s teacher-rated reactive aggression, but not teacher-rated proactive aggression. The relation of peer victimization to increased reactive aggression was, however, moderated by recent ˉ not previous ˉ reciprocal friends’ similarly aggressive characteristics. These findings, however, tended to be mostly true for boys, but not for girls. The findings are discussed in terms of their theoretical and practical implications for victimized children’s risk of displaying reactive and proactive aggressive behaviors. This research was made possible by grants from the Social Sciences and Humanities Research Council of Canada, the Fonds Concerté pour l’Aide à la Recherche, the Fonds Québécois de la Recherche sur la Société et la Culture, the Canadian Institutes of Health Research, and the Fonds de Recherche en Santé du Québec.     

Assessing the adequacy of postexperimental inquiries in deception research and the factors that promote participant honesty

The primary aim of this research was to assess the adequacy of postexperimental inquiries (PEI) used in deception research, as well as to examine whether mood state, reward, or administering the PEI as a face-to-face interview or computer survey impacts participants’ willingness to divulge suspicion or knowledge about a study. We also sought to determine why participants are not always forthcoming on the PEI. Study 1 examined how frequently PEIs are included in research and found that most researchers employing deception do use a PEI. Studies 2 and 3 showed that participants are often unwilling to divulge suspicion or awareness of deception or to admit to having prior knowledge about a study, though offering a reward and completing the PEI on a computer modestly improved awareness and admission rates. Study 4 indicated several reasons why participants may not reveal suspicion or knowledge about a study on the PEI.     

The mental representation and processes of spatial deductive reasoning with diagrams and sentences

This study has two main objectives. The first is to specify the nature of the mental representation and processes underlying spatial reasoning with diagrams and sentences. The second is to investigate whether mental representations reproduce geometrical relations relative to spatial reference frames. Forty participants solved 64 spatial reasoning problems that were displayed using diagrams or sentences. Problems varied with respect to their logical structure and geometrical content. We measured the premise's inspection times, the responses, and the response times. Problems were significantly (p < .01) easier to represent and solve when displayed as diagrams than as sentences, indicating that participants constructed mental models. Mental representations and spatial deductions also varied consistently with the geometrical content, suggesting that mental models reproduced this content relative to a viewer‐centred reference frame.     

Methodological Problems in Operant Learning Research with Human Infants

A great number of the recent studies on infant operant learning use the mobile conjugate reinforcement paradigm with 2- and 3-month-old infants. This paradigm has proved to be adequate for the study of learning and the transfer of learning. However, difficulties linked to the high attrition rates of subjects, and the variability in performance are frequently observed in studies using other paradigms or in studies with older infants (4–5-month-olds). The problems noted in a group of studies seem to be related to important methodological issues such as the brevity of the learning sessions, the choice of dependent measures, and the management of variability in performance. The use of single-subject designs and the use of variables encountered in infants' daily learning experiences may be the solution to some of the problems.     

Transfer of inhibition after serial and simultaneous feature negative discrimination training

Three experiments examined the nature of inhibitory learning in Pavlovian simultaneous (A+, XA-) and serial (A+, X → A-) feature negative discrimination prodecures in a conditioned suppression situation with rat subjects. The feature (X) trained with simultaneous procedures readily inhibited suppression conditioned to another excitor (B) that was not involved in the feature negative discrimination with X. But the feature trained with serial procedures showed little or no ability to inhibit suppression conditioned to other excitors. These results were obtained with both between- and within-subjects designs, with a variety of test procedures, and after extinction of the A excitor used to establish the inhibition to X. They suggest that nature of the inhibition learned in feature negative discriminations depends on the temporal arrangement of stimuli. We favored the possibility that inhibitors established using simultaneous stimulus arrangements modulate behavior by acting on a representation of the unconditioned stimulus, but inhibitors established with serial procedures act on particular conditioned stimulus-unconditioned stimulus associations.     

Links Between Early Personal Characteristics,Longitudinal Profiles of Peer Victimization in School and Victimization in College or at Work

Research on Child and Adolescent Psychopathology - This study used a longitudinal design from age six through age 19 (N?=?1206 (603 girls)) to examine the associations between...     

Locus of the redundant-signals effect in bimodal divided attention: A neurophysiological analysis

We reanalyzed the data from the study of Lamarre, Busby, and Spidalieri (1983). In that study, the activity of single neurons in area 4 of the motor cortex was recorded during a bimodal detection task in which a monkey (Macaca mulatta)had to respond as quickly as possible to a visual or an auditory signal or to both (redundant trials). Manual responses on redundant trials were speeded by the presence of both signals, as is typically found. The times between signal onsets and the first changes in neuronal activity were also speeded by redundant signals, but there was no difference between redundant-signals and single-signal trials in the time between the change in neuronal activity and movement onset. These results suggest that late motor processes are not speeded by redundant signals in bimodal detection tasks.     

Sex differences in early verbal and non‐verbal cognitive development

The present study of over 3000 2‐year‐old twin pairs used a sex‐limitation model to examine genetic and environmental origins of sex differences in verbal and non‐verbal cognitive ability. Girls scored significantly higher on both measures (p<0.0001), although gender only accounted for approximately 3% of the variance in verbal ability and 1% of the variance in non‐verbal cognitive ability. For the verbal measure boys showed greater heritability than girls. Also the twin‐pair correlation is significantly lower for opposite‐sex twins than for non‐identical same‐sex twins. This indicates that individual differences in verbal ability include some sex‐specific factors. Non‐verbal cognitive ability did not differ in aetiology for boys and girls. We conclude that genetic and environmental influences differ for girls and boys for early verbal but not non‐verbal development.