Male Wistar rats show individual differences in an animal model of conformity

Conformity refers to the act of changing one’s behaviour to match that of others. Recent studies in humans have shown that individual differences exist in conformity and that these differences are related to differences in neuronal activity. To understand the neuronal mechanisms in more detail, animal tests to assess conformity are needed. Here, we used a test of conformity in rats that has previously been evaluated in female, but not male, rats and assessed the nature of individual differences in conformity. Male Wistar rats were given the opportunity to learn that two diets differed in palatability. They were subsequently exposed to a demonstrator that had consumed the less palatable food. Thereafter, they were exposed to the same diets again. Just like female rats, male rats decreased their preference for the more palatable food after interaction with demonstrator rats that had eaten the less palatable food. Individual differences existed for this shift, which were only weakly related to an interaction between their own initial preference and the amount consumed by the demonstrator rat. The data show that this conformity test in rats is a promising tool to study the neurobiology of conformity.     

The end-state comfort effect facilitates joint action

Motor experts can accurately predict the future actions of others by observing their movements. This report describes three experiments that investigate such predictions in everyday object manipulations and test whether these predictions facilitate responses to the actions of others. Observing video excerpts showing an actor reaching for a vertically mounted dial, participants in Experiment 1 needed to predict how the actor would rotate it. Their predictions were specific to the direction and extent of the dial rotation and improved proportionate to the length of the video clip shown. Testing whether such predictions facilitate responses, in the subsequent experiments responders had to undo an actor's actions, back-rotating a dial (Exp 2) and a bar (Exp 3). The responders' actions were initiated faster when the actors' movements obeyed the so-called end-state comfort principle than when they did not. Our experiments show that humans exploit the end-state comfort effect to tweak their predictions of the future actions of others. The results moreover suggest that the precision of these predictions is mediated by perceptual learning rather than by motor simulation.     

Psychometric Evaluation of the Borderline Personality Disorder Severity Index-IV-Adolescent Version and Parent Version

The Borderline Personality Disorder Severity Index-IV-adolescent and parent versions (BPDSI-IV-ado/p) are DSM-IV based semi-structured interviews for the assessment of the severity of symptoms of borderline personality disorder (BPD) in adolescents. The present study evaluates the psychometric properties of the BPDSI-IV-ado/p. The interviews were administered to 122 adolescents, aged 14-19 years and their parents/caretakers who were referred to mental health centres for emotion regulation problems, and to 45 healthy controls. The interrater reliability and internal consistency of all nine subscales (following the nine BPD symptoms in DSM-IV) proved to be good to excellent. Discriminant, concurrent, and construct validity were satisfactory. Cut-off scores that optimize sensitivity and specificity were derived. Informant agreement between adolescents and parents/caretakers was modest. The results of this study suggest that the BPDSI-IV adolescent and parent versions are valid and reliable instruments for the assessment of BPD symptom severity in adolescents.     

Relations between emotions,display rules,social motives,and facial behaviour

We report research on the relations between emotions, display rules, social motives, and facial behaviour. In Study 1 we used a questionnaire methodology to examine how respondents would react to a funny or a not funny joke told to them by a close friend or a stranger. We assessed display rules and motivations for smiling and/or laughing. Display rules and social motives (partly) mediated the relationship between the experimental manipulations and self‐reported facial behaviour. Study 2 was a laboratory experiment in which funny or not funny jokes were told to participants by a male or female stranger. Consistent with hypotheses, hearing a funny joke evoked a stronger motivation to share positive affect by showing longer Duchenne smiling. Contrary to hypotheses, a not funny joke did not elicit greater prosocial motivation by showing longer “polite” smiling, although such a smiling pattern did occur. Rated funniness of the joke and the motivation to share positive affect mediated the relationship between the joke manipulation and facial behaviour. Path analysis was used to explore this mediating process in greater detail.