Left-handedness and male-male competition: Insights from fighting and hormonal data

Male-male competition can shape some behavioral or morphological traits of males. Here we investigate if this competition could play a role in the persistence of the polymorphism of handedness in human populations. A negative frequency-dependent selection mechanism has been hypothesized, based on the fact that left-handed men may benefit from a "surprise" advantage during fighting interactions because they are rare in human populations. This advantage may thereby enhance the probability of survival of left- handed men and/or their reproductive success through an increase in social status. In this study, we first explored the association between hand preference and lifetime fighting behavior in a population of 1,161 French men. No effect of hand preference on the probability of fighting was detected, suggesting that the innate propensity to fight does not differ between left- and right-handers. However, among men who had been involved in at least one fight during their lifetime, left-handers reported significantly more fights than right-handers. To explore the biological basis of this behavior, we also investigated the testosterone concentration in saliva samples from 64 French university students. Consistent with frequencies of fights, we found a significantly higher average testosterone concentration in left-handers than in right-handers. We suggest that these behavioral and hormonal differences may be acquired throughout life due to previous experiences in a social context and may favor the persistence of left-handers in humans.     

A New Measure to Assess Psychopathic Personality in Children: The Child Problematic Traits Inventory

Understanding the development of psychopathic personality from childhood to adulthood is crucial for understanding the development and stability of severe and long-lasting conduct problems and criminal behavior. This paper describes the development of a new teacher rated instrument to assess psychopathic personality from age three to 12, the Child Problematic Traits Inventory (CPTI). The reliability and validity of the CPTI was tested in a Swedish general population sample of 2,056 3- to 5-year-olds (mean age?=?3.86; SD?=?.86; 53 % boys). The CPTI items loaded distinctively on three theoretically proposed factors: a Grandiose-Deceitful Factor, a Callous-Unemotional factor, and an Impulsive-Need for Stimulation factor. The three CPTI factors showed reliability in internal consistency and external validity, in terms of expected correlations with theoretically relevant constructs (e.g., fearlessness). The interaction between the three CPTI factors was a stronger predictor of concurrent conduct problems than any of the three individual CPTI factors, showing that it is important to assess all three factors of the psychopathic personality construct in early childhood. In conclusion, the CPTI seems to reliably and validly assess a constellation of traits that is similar to psychopathic personality as manifested in adolescence and adulthood.     

Is the principle of minimization of secondary moments validated during various fingertip force production conditions?

During the application of fingertip forces with simultaneous flexion of the four fingers, namely index, middle, ring, and little fingers, a stable force sharing among fingers is adopted. Several studies have hypothesized that this stable force sharing is established to minimize unnecessary rotational moments (different from the main flexion moments). This principle labeled "minimization of secondary moments" is presented in the literature as a principle used by the central nervous system to solve musculoskeletal redundancy. However, this principle has only been tested with one solicited degree of freedom and in one finger posture. Our study tests this principle with various degrees of freedom solicited as secondary moments and in two different finger postures. Participants (n=6) were asked to apply a downward vertical force using their four fingers with the forearm placed in two different configurations: a "horizontal" condition (involving flexion/extension and pronation/supination at the wrist joint) and a "vertical" condition (involving flexion/extension and radial/ulnar deviation at the wrist joint). Additionally, two finger postures were tested in each forearm configuration: in the first, the distal inter-phalangeal joints (DIP) were extended and the proximal inter-phalangeal joints (PIP) highly flexed. In the second finger posture, both DIP and PIP joints were flexed. The resultant four-finger force and the relative involvement of each finger in the resultant four-finger force (force sharing) were analyzed. Results showed that the finger postures did not influence the finger force sharing, showing that the minimization of the secondary moment principle was stable among the finger joint angle configurations. Nonetheless, the relative involvement of each finger was dependent on the secondary degree of freedom solicited (pronation/supination vs. radial/ulnar). The modifications of the finger force sharing between the "horizontal" and "vertical" conditions were in accordance with the principle of minimization of the secondary moments.     

Are perceived school climate dimensions predictive of students’ engagement?

Students’ engagement is known to be associated with academic success and to prevent school dropouts. While many studies have considered this variable when examining school trajectories, more research is needed to investigate the factors that may sustain and promote engagement in school, regarded as a multidimensional construct (affective vs. cognitive vs. behavioral engagement). In the present cross-sectional study, associations between students’ perceptions of school climate dimensions and their level of engagement were explored. The differential effects on these associations of sex and social background were also examined. Results from a sample of 955 high-school students showed that a model incorporating six dimensions of perceived school climate explained a large proportion of the variance in students’ engagement, especially affective engagement. The perceived climate of relations between teachers and students appeared to be highly predictive of students’ engagement. Analyses also revealed that the predictiveness of school climate factors for affective, cognitive and behavioral engagement varied slightly according to sex and social background. These results highlight important levers associated with students’ engagement in school.     

Contrasting Grammatical and Lexical Determiners

This paper investigates the difference between the production of grammatical determiners and lexical determiners in the production of adjective-noun phrases (NPs) in Danish. Models of sentence processing (Garrett in Psychology of learning and motivation, Academic press, New York, pp 133–177, 1975; Bock in J Mem Lang 26(2):119–137, 1987) suggest that the phonological encoding stage of grammatical items can only be specified once lexical items have been phonologically encoded. In their usage-based linguistic theory of the grammar-lexicon distinction, Boye and Harder (Lang 88(1):1–44, 2012) propose that this later encoding of grammatical elements is motivated by two specific features of grammatical elements. The first feature, dependence, is that grammatical items (morphemes, words, constructions) cannot be produced in isolation, but are always dependent on a lexical host item. This feature entails a more complex processing which might lead to longer reaction times when comparing the production of NPs with a grammatical determiner to a lexical one. Additionally, a more complex processing might lead to a lower accuracy rate for the grammatical condition relative to the lexical one. The second feature, low prominence, is that grammatical items code background information and therefore cannot convey the main point of a linguistic message. Less focus on grammatical elements might lead to a lower accuracy rate for the production of grammatical elements relative to lexical ones. Those predictions were tested in a task comparing the production of Danish grammatical determiners (indefinite articles) with the production of lexical ones (numerals, which are homonymous with the articles except for a stress difference) in similar contexts. Group-based analyses were performed in order to take inter-individual differences into account. The results show that the two features as proposed by Boye and Harder (2012) are only revealed for the fastest speakers group but not the slower ones.