Testing for Changes in Kendall's Tau

For a bivariate time series $((X_i,Y_i))_{i=1,...,n}$ we want to detect whether the correlation between $X_i$ and $Y_i$ stays constant for all $i = 1,...,n$. We propose a nonparametric change-point test statistic based on Kendall's tau and derive its asymptotic distribution under the null hypothesis of no change by means a new U-statistic invariance principle for dependent processes. The asymptotic distribution depends on the long run variance of Kendall's tau, for which we propose an estimator and show its consistency. Furthermore, assuming a single change-point, we show that the location of the change-point is consistently estimated. Kendall's tau possesses a high efficiency at the normal distribution, as compared to the normal maximum likelihood estimator, Pearson's moment correlation coefficient. Contrary to Pearson's correlation coefficient, it has excellent robustness properties and shows no loss in efficiency at heavy-tailed distributions. We assume the data $((X_i,Y_i))_{i=1,...,n}$ to be stationary and P-near epoch dependent on an absolutely regular process. The P-near epoch dependence condition constitutes a generalization of the usually considered $L_p$-near epoch dependence, $p \ge 1$, that does not require the existence of any moments. It is therefore very well suited for our objective to efficiently detect changes in correlation for arbitrarily heavy-tailed data

Disruptive behavior disorders and psychopathic traits in adolescents:Empathy-related responses to witnessing animal distress

Cruelty to animals is a symptom of conduct disorder and associated with psychopathic traits in childhood. One of the factors thought to contribute to animal cruelty is reduced empathy and concern for the well-being of animals. A first aim of this study was to examine empathy towards animals in distress in male adolescents with disruptive behavior disorders (DBD) and high or low psychopathic traits, and normal controls (NC). Psychopathic traits were assessed by the Antisocial Process Screening Device (APSD). Respondents were exposed to a short film clip depicting a baby bear in distress. Heart rate (HR) responses were monitored during film exposure. Afterwards, respondents were asked to report the emotions they had observed and experienced. Contrary to expectations based on research on human empathy, no group differences were found in empathy-related responses to witnessing animal distress. Both DBD groups and normal controls observed equal levels of distress in the baby bear, experienced as much empathy and sympathy, and showed similar levels of HR reduction during the most dramatic scene. Results suggest that empathy for humans does not generalize to animals, and vice versa. A second aim was to examine the associations between empathy-related responses and the broad concept of psychopathy as well as its dimensions. The relationships were different and for the most part reversed in the NC and DBD groups. Group proved to be an important moderating factor, indicating that results obtained within a sample of healthy adolescents do not generalize to adolescents with DBD, and vice versa

Subnormal short‐latency facial mimicry responses to dynamic emotional facial expressions in male adolescents with disruptive behavior disorders and callous‐unemotional traits

Using still pictures of emotional facial expressions as experimental stimuli, reduced amygdala responses or impaired recognition of basic emotions were repeatedly found in people with psychopathic traits. The amygdala also plays an important role in short‐latency facial mimicry responses. Since dynamic emotional facial expressions may have higher ecological validity than still pictures, we compared short‐latency facial mimicry responses to dynamic and static emotional expressions between adolescents with psychopathic traits and normal controls. Facial EMG responses to videos or still pictures of emotional expressions (happiness, anger, sadness, fear) were measured. Responses to 500‐ms dynamic expressions in videos, as well as the subsequent 1500‐ms phase of maximal (i.e., static) expression, were compared between male adolescents with disruptive behavior disorders and high (n = 14) or low (n = 17) callous‐unemotional (CU) traits, and normal control subjects (n = 32). Responses to still pictures were also compared between groups. EMG responses to dynamic expressions were generally significantly smaller in the high‐CU group than in the other two groups, which generally did not differ. These group differences gradually emerged during the 500‐ms stimulus presentation period but in general they were already seen a few hundred milliseconds after stimulus onset. Group differences were absent during the 1500‐ms phase of maximal expression and during exposure to still pictures. Subnormal short‐latency mimicry responses to dynamic emotional facial expressions in the high‐CU group might have negative consequences for understanding emotional facial expressions of others during daily life when human facial interactions are primarily dynamic

Boys with oppositional defiant disorder/conduct disorder show impaired adaptation during stress: an executive functioning study

Evidence for problems in executive functioning (EF) in children with oppositional defiant disorder/conduct disorder (ODD/CD) is mixed and the impact stress may have on EF is understudied. Working memory, sustained attention, inhibition and cognitive flexibility of boys with ODD/CD (n = 65) and non-clinical controls (n = 32) were examined under typical and stressful test conditions. Boys with ODD/CD showed impaired working memory under typical testing conditions, and impairments in working memory and sustained attention under stressful conditions. In contrast to controls, performance on sustained attention, cognitive flexibility and inhibition was less influenced by stress in boys with ODD/CD. These results suggest that boys with ODD/CD show impairments in adaptation to the environment whereas typically developing boys show adaptive changes in EF

Emotion regulation difficulties in boys with oppositional defiant disorder/conduct disorder and the relation with comorbid autism traits and attention deficit traits

Previous research has pointed towards a link between emotion dysregulation and aggressive behavior in children. Emotion regulation difficulties are not specific for children with persistent aggression problems, i.e. oppositional defiant disorder or conduct disorder (ODD/CD), children with other psychiatric conditions, such as autism spectrum disorders or attention-deficit/hyperactivity disorder, have emotion regulation difficulties too. On a behavioral level some overlap exists between these disorders and comorbidity is high. The aim of this study was therefore twofold: 1) to examine emotion regulation difficulties in 65 boys with ODD/CD in comparison to a non-clinical control group (NC) of 38 boys (8–12 years) using a performance measure (Ultimatum Game), parent report and self-report, and 2) to establish to what extent emotion regulation in the ODD/CD group was correlated with severity of autism and/or attention deficit traits. Results on the Ultimatum Game showed that the ODD/CD group rejected more ambiguous offers than the NC group, which is seen as an indication of poor emotion regulation. Parents also reported that the ODD/CD group experienced more emotion regulation problems in daily life than the NC group. In contrast to these cognitive and behavioral measures, self-reports did not reveal any difference, indicating that boys with ODD/CD do not perceive themselves as having impairments in regulating their emotions. Emotional decision making within the ODD/CD group was not related to variation in autism or attention deficit traits. These results support the idea that emotion dysregulation is an important problem within ODD/CD, yet boys with ODD/CD have reduced awareness of this