David Leiva

Quantifying social asymmetric structures.

Many social phenomena involve a set of dyadic relations among agents whose actions may be dependent. Although individualistic approaches have frequently been applied to analyze social processes, these are not generally concerned with dyadic relations, nor do they deal with dependency. This article describes a mathematical procedure for analyzing dyadic interactions in a social system. The proposed method consists mainly of decomposing asymmetric data into their symmetric and skew-symmetric parts. A quantification of skew symmetry for a social system can be obtained by dividing the norm of the skew-symmetric matrix by the norm of the asymmetric matrix. This calculation makes available to researchers a quantity related to the amount of dyadic reciprocity. With regard to agents, the procedure enables researchers to identify those whose behavior is asymmetric with respect to all agents. It is also possible to derive symmetric measurements among agents and to use multivariate statistical techniques.

Testing reciprocity in social interactions: a comparison between the directional consistency and skew-symmetry statistics.

In the present article, we focus on two indices that quantify directionality and skew-symmetrical patterns in social interactions as measures of social reciprocity: the directional consistency (DC) and skew-symmetry indices. Although both indices enable researchers to describe social groups, most studies require statistical inferential tests. The main aims of the present study are first, to propose an overall statistical technique for testing null hypotheses regarding social reciprocity in behavioral studies, using the DC and skew-symmetry statistics (Φ) at group level; and second, to compare both statistics in order to allow researchers to choose the optimal measure depending on the conditions. In order to allow researchers to make statistical decisions, statistical significance for both statistics has been estimated by means of a Monte Carlo simulation. Furthermore, this study will enable researchers to choose the optimal observational conditions for carrying out their research, since the power of the statistical tests has been estimated.

Does fear extinction in the laboratory predict outcomes of exposure therapy? A treatment analog study

Fear extinction models have a key role in our understanding of anxiety disorders and their treatment with exposure therapy. Here, we tested whether individual differences in fear extinction learning and fear extinction recall in the laboratory were associated with the outcomes of an exposure therapy analog (ETA). Fifty adults with fear of spiders participated in a two-day fear-learning paradigm assessing fear extinction learning and fear extinction recall, and then underwent a brief ETA. Correlational analyses indicated that enhanced extinction learning was associated with better ETA outcome. Our results partially support the idea that individual differences in fear extinction learning may be associated with exposure therapy outcome, but suggest that further research in this area is needed.

The MABIC project: An effectiveness trial for reducing risk factors for eating disorders.

Challenges in the prevention of disordered eating field include moving from efficacy to effectiveness and developing an integrated approach to the prevention of eating and weight-related problems. A previous efficacy trial indicated that a universal disordered eating prevention program, based on the social cognitive model, media literacy educational approach and cognitive dissonance theory, reduced risk factors for disordered eating, but it is unclear whether this program has effects under more real-world conditions. This effectiveness trial tested whether this program has effects when previously trained community providers in an integrated approach to prevention implement the intervention. The research design involved a multi-center non-randomized controlled trial with baseline, post-test and 1-year follow-up measures. The sample included girls in the 8th grade from six schools (n = 152 girls) in a city near Barcelona (intervention group), and from eleven schools (n = 413 girls) in four neighboring towns (control group). The MABIC risk factors of disordered eating were assessed as main outcomes. Girls in the intervention group showed significantly greater reductions in beauty ideal internalization, disordered eating attitudes and weight-related teasing from pretest to 1-year follow-up compared to girls in the control group, suggesting that this program is effective under real-world conditions

Some common indices of group diversity: upper boundaries.

Workgroup diversity can be conceptualized as variety, separation, or disparity. Thus, the proper operationalization of diversity depends on how a diversity dimension has been defined. Analytically, the minimal diversity must be obtained when there are no differences on an attribute among the members of a group, however maximal diversity has a different shape for each conceptualization of diversity. Previous work on diversity indexes indicated maximum values for variety (e.g., Blaus index and Teachmans index), separation (e.g., standard deviation and mean Euclidean distance), and disparity (e.g., coefficient of variation and the Gird coefficient of concentration), although these maximum values are not valid for all group characteristics (i.e., group size and group size parity) and attribute scales (i.e., number of categories). We demonstrate analytically appropriate upper boundaries for conditional diversity determined by some specific group characteristics, avoiding the bias related to absolute diversity. This will allow applied researchers to make better interpretations regarding the relationship between group diversity and group outcomes.

Mediterranean diet adherence among Catalonian adolescents: socio-economic and lifestyle factors

AIM This study aims to describe the adherence to the Mediterranean diet (MD), using the KIDMED questionnaire, in a sample of Catalonian adolescents and to assess the association between the MD adherence and socio-economic and lifestyle behaviours. MATERIAL AND METHODS Data are part of a multi-centre longitudinal study designed for the reduction of risk factors of eating and weight-related problems in adolescents. Here, a cross-sectional analysis was performed with the baseline data, academic period 2010-11. The participants were 1,502 adolescents recruited from 11 schools from the province of Barcelona. RESULTS AND CONCLUSIONS The results showed a higher level of MD adherence when parents had higher educational level, and when adolescents reported a low level of screen-time, and high weekly physical activity.

Measuring and making decisions for social reciprocity

Social reciprocity may explain certain emerging psychological processes likely to be founded on dyadic relations. Although indexes and statistics have been proposed to measure and make statistical decisions regarding social reciprocity in groups, these tools were generally developed to identify association patterns rather than to quantify the discrepancies between what each individual addresses to his or her partners and what is received from those partners in return. Additionally, social researchers’ interest extends beyond measuring groups at the global level because dyadic and individual measurements are also necessary for proper descriptions of social interactions. This study is concerned with a new statistic for measuring social reciprocity at the global level and with decomposing that statistic in order to identify which dyads and individuals account for a significant part of asymmetry in social interactions. In addition to a set of indexes, some exact analytical results are derived, and a way of making statistical decisions is proposed.

Fighting over burrows: the emergence of dominance hierarchies in the Norway lobster (Nephrops norvegicus)

ABSTRACT Animals fight over resources such as mating partners, territory, food or shelter and repeated contests lead to stable social hierarchies in different phyla. The group dynamics of hierarchy formation are not characterized in the Norway lobster (Nephrops norvegicus). Lobsters spend most of the day in burrows and forage outside of them according to a diel (i.e. 24 h-based) activity rhythm. Here, we use a linear and generalized mixed model approach to analyse, in seven groups of four male lobsters, the formation of dominance hierarchies and rank-related changes in burrowing behaviour. We show that hierarchies emerge within 1–3 days and increase in steepness over a period of 5 days, while rank changes and number of fights gradually decrease over a 5-day period. The rank position determined by open area fights predicts the outcome of fights over burrows, the time spent in burrows, and the locomotor activity levels. Dominant lobsters are more likely to evict subordinate lobsters from their burrows and are more successful in defending their own burrows. They spend more time in burrows and display lower levels of locomotor activity outside the burrow. Lobsters do not change their diel activity rhythms as a result of a change in rank, and all tested individuals showed higher activity at night and dusk compared with dawn and daytime. We discuss how behavioural changes in burrowing behaviour could lead to rank-related benefits such as reduced exposure to predators and energy savings. Summary: Dominant Norway lobsters profit from their rank in a social hierarchy by gaining increased access to burrows and by reducing activity outside the shelters as the hierarchy emerges.

Bias and standard error for social reciprocity measurements.

The directional consistency and skew-symmetry statistics have been proposed as global measure of social reciprocity. Although both measures can be useful for quantifying social reciprocity, researchers need to know whether these estimators are biased in order properly to assess descriptive results. That is, if estimators are biased, researchers should compare actual values with expected values under the specified null hypothesis. Furthermore, standard errors are needed to enable suitable assessment of discrepancies between actual and expected values. This paper aims to derive some exact and approximate expressions in order to obtain bias and standard error values for both estimators for round-robin designs, although the results can also be extended to other reciprocal designs.

Brain lesion scores obtained using a simple semi-quantitative scale from MR imaging are associated with motor function, communication and cognition in dyskinetic cerebral palsy

Purpose To characterise brain lesions in dyskinetic cerebral palsy (DCP) using the semi-quantitative scale for structural MRI (sqMRI) and to investigate their relationship with motor, communication and cognitive function. Materials and methods Thirty-nine participants (19 females, median age 21y) with DCP were assessed in terms of motor function, communication and a variety of cognitive domains. Whole-head magnetic resonance imaging (MRI) was performed including T1-MPRAGE, T2 turbo spin echo (axial plane), and fluid attenuated inversion recovery images (FLAIR). A child neurologist visually assessed images for brain lesions and scored these using the sqMRI. Ordinal, Poisson and binomial negative regression models identified which brain lesions accounted for clinical outcomes. Results Brain lesions were most frequently located in the ventral posterior lateral thalamus and the frontal lobe. Gross (B = 0.180, p < .001; B = 0.658, p < .001) and fine (B = 0.136, p = .003; B = 0.540, p < .001) motor function were associated with global sqMRI score and parietal involvement. Communication functioning was associated with putamen involvement (B = 0.747, p < .028). Intellectual functioning was associated with global sqMRI score and posterior thalamus involvement (B = −0.018, p < .001; B = −0.192, p < .001). Selective attention was associated with global sqMRI score (B = −0.035, p < .001), parietal (B = −0.063, p = .023), and corpus callosum involvement (B = −0.448, p < .001). Visuospatial and visuoperceptive abilities were associated with global sqMRI score (B = −0.078, p = .007) and medial dorsal thalamus involvement (B = −0.139, p < .012), respectively. Conclusions Key clinical outcomes in DCP are associated with specific observable brain lesions as indexed by a simple lesion scoring system that relies only on standard clinical MRI.