Age-Associated Differences in Positional Variability Are Greater With the Lower Limb

The authors’ purpose was to determine the interaction of age and limb used on positional variability at different loads. Eleven young adults and 10 older adults were asked to accurately match and maintain a horizontal target line with 5° abduction of their index finger and 5° dorsiflexion of their ankle for 20 s at loads ranging from 2 to 50% of the maximal load that could be lifted with each limb. The visual gain was kept constant at 1° (visual angle). Positional variability was greater in older adults for both limbs, nonetheless age-associated differences were greater for the ankle dorsiflexion task compared with the abduction of the index finger task. In addition, we found that, independent of age, motor output variability was greater with the lower limb. These results provide novel evidence that older adults may exhibit greater impairments in motor control with the foot compared with the finger. Furthermore, these findings support the idea, using a different task than previous literature, that the lower limb has greater motor output variability than the upper limb.     

Work and Rest Variables in the Acquisition of Psychomotor Tracking Skill

College students (75 men, 75 women) matched in preliminary performance of 100 sec on the rotary pursuit apparatus were randomly assigned to five experimental groups. Their work/rest ratios, measured in seconds, were: 20/20, 30/30, 60/60, 90/90,120/120. All subjects received 30 min of total practice time after the matching trial. There was a significant practice effect and a significant practice x conditions interaction, but no main effect due to the cycles’ length or number. The decay rate of reactive inhibition (lr) is probably independent of its prior growth level; hence postrest residual lr is proportional to prerest accumulation. Partly because they generated lr in hypothetically greater amounts, women were significantly less proficient on the average than men, and sex interacted with practice. Although males had higher initial and final levels of ability than females, the two sexes’ acquisition curves showed the same rate parameters in our mathematical model.     

Developmental trajectory of intersubjectivity in the second and third year of life: Study of fixed-population and random-individual effects

Colwyn Trevarthen claimed that babies have an intrinsic motivation to communicate and engage with others that he called intersubjectivity. Around the ninth month of life, this motivation changes and passes from person-to-person dyadic (primary intersubjectivity) to triangulate a person–person–object relationship (secondary intersubjectivity). Despite the scientific consensus on this developmental leap, few empirical studies explore the trajectory of this more complex form of intersubjectivity between the second and third year of life. One hundred and fifteen free play sessions from 27 mother–child dyads (13 girls and 14 boys) between 9 and 37 months were filmed and were categorized based on the Level of Intersubjective Attunement Scale. The data were analysed using a linear mixed-effects model. Results show both a population trajectory of the levels of intersubjective attunement and random individual differences. We discuss these results in relation to the binomial typical developmental route and interindividual variability.     

Holistic thinking and air traffic controllers' decision making in conflict resolution

When facing potential conflicts, whether to make interventions is an important decision for air traffic controllers and vital for aviation safety and efficiency. While many task-related factors in influencing such decisions have been identified, the large portion of individual differences has remained insufficiently explained. This paper proposes that controllers with a more holistic thinking style will be more likely to make interventions because they envision more uncertainties in the system which can lead to a higher level of perceived risk and a greater likelihood to take proactive measures. To test these hypotheses, forty-two licensed controllers were invited to complete a questionnaire measuring holistic thinking style and later a conflict detection/resolution task. Multilevel regression analyses showed that (1) when the real risk level (the minimum lateral distance between two converging aircraft) dropped, controllers who think more holistically still tended to maintain a higher risk perception level (perceived likelihood of aircraft collision in the future) which lead to a higher intervention ratio and (2) even when real and perceived risk levels were controlled, those who think more holistically were more likely to make interventions. These findings are discussed with reference to literature in cognitive style, risk perception and workload management. Potential implications for personnel selection and training are also discussed.     

Relating lab to life: Decrements in attention over time predict math productivity among children with ADHD

A child’s ability to sustain attention over time (AOT) is critical in attention-deficit/hyperactivity disorder (ADHD), yet no prior work has examined the extent to which a child’s decrement in AOT on laboratory tasks relates to clinically-relevant behavior. The goal of this study is to provide initial evidence for the criterion validity of laboratory assessments of AOT. A total of 20 children with ADHD (7–12 years of age) who were enrolled in a summer treatment program completed two lab attention tasks (a continuous performance task and a self-paced choice discrimination task) and math seatwork. Analyses focused on relations between attention task parameters and math productivity. Individual differences in overall attention (OA) measures (averaged across time) accounted for 23% of the variance in math productivity, supporting the criterion validity of lab measures of attention. The criterion validity was enhanced by consideration of changes in AOT. Performance on all laboratory attention measures deteriorated as time-on-task increased, and individual differences in the decrement in AOT accounted for 40% of the variance in math productivity. The only variable to uniquely predict math productivity was from the self-paced choice discrimination task. This study suggests that attention tasks in the lab do predict a clinically-relevant target behavior in children with ADHD, supporting their use as a means to study attention processes in a controlled environment. Furthermore, this prediction is improved when attention is examined as a function of time-on-task and when the attentional demands are consistent between lab and life contexts.     

Adverse childhood experiences and autonomic regulation in response to acute stress: the role of the sympathetic and parasympathetic nervous systems

Background and objectives: After a previous report demonstrated blunted heart rate (HR) reactivity in association with adverse childhood experiences (ACEs) [Voellmin, A., Winzeler, K., Hug, E., Wilhelm, F. H., Schaefer, V., Gaab, J.,?…?Bader, K. (2015). Blunted endocrine and cardiovascular reactivity in young healthy women reporting a history of childhood adversity. Psychoneuroendocrinology, 51, 58–67. doi:10.1016/j.psyneuen.2014.09.008], the present analysis aimed at clarifying the role of the sympathetic and parasympathetic branches of the autonomic nervous system in this relationship.

Design and Methods: One hundred eighteen healthy young women provided data on ACEs and underwent psychosocial stress testing. Systolic blood pressure (SBP) and respiratory sinus arrhythmia (RSA, quantified by high-frequency HR variability) were assessed as measures of sympathetic and parasympathetic cardiovascular activity, respectively. A mediation model was calculated to test the indirect effects of ACEs on HR via SBP and RSA.

Results: The effect of ACEs on HR reactivity was mediated by SBP reactivity but not by RSA reactivity. ACEs were associated with reduced SBP at rest.

Conclusions: ACEs were associated with down-regulation in a measure of sympathetic but no alteration in a measure of parasympathetic cardiovascular stress reactivity in adulthood. Future research will need to clarify whether this indicates risk or resilience.     

Measuring category intuitiveness in unconstrained categorization tasks

What makes a category seem natural or intuitive? In this paper, an unsupervised categorization task was employed to examine observer agreement concerning the categorization of nine different stimulus sets. The stimulus sets were designed to capture different intuitions about classification structure. The main empirical index of category intuitiveness was the frequency of the preferred classification, for different stimulus sets. With 169 participants, and a within participants design, with some stimulus sets the most frequent classification was produced over 50 times and with others not more than two or three times. The main empirical finding was that cluster tightness was more important in determining category intuitiveness, than cluster separation. The results were considered in relation to the following models of unsupervised categorization: DIVA, the rational model, the simplicity model, SUSTAIN, an Unsupervised version of the Generalized Context Model (UGCM), and a simple geometric model based on similarity. DIVA, the geometric approach, SUSTAIN, and the UGCM provided good, though not perfect, fits. Overall, the present work highlights several theoretical and practical issues regarding unsupervised categorization and reveals weaknesses in some of the corresponding formal models.     

Deviant but desirable: Group variability and evaluation of atypical group members

Two studies investigated how group variability affects reactions to atypical group members. In Study 1 (N = 65) we manipulated group variability and found that an atypical group member was evaluated more positively when the group was heterogeneous than when the group was homogeneous. In Study 2 (N = 276) we also manipulated group value and found a significant interaction whereby an atypical group member was evaluated more positively when the group was homogeneous and group members valued heterogeneity, but was evaluated more negatively when the group was heterogeneous and group members valued homogeneity. The results suggest that deviant or atypical members will not inevitably be rejected by the group, but rather that reactions to deviance are shaped and guided by the dynamic relationship between how the group is perceived by its members and their ideological beliefs about what is good for the group.     

Tryptophan and interpersonal spin

Increased serotonergic activity is often described as increasing the inhibition of behaviors. This study examined the more general hypothesis that increased serotonergic activity produces greater control over social behavior. Participants were drawn from two samples, individuals elevated on irritability and individuals unselected on personality characteristics. Individuals participated in a double blind cross-over design, providing event contingent records about their behavior during two 9-day periods which involved taking tryptophan or placebo. When taking tryptophan (which increases serotonergic activity), within-person variability among social behaviors across events (i.e., interpersonal spin) was reduced for irritable individuals, particularly those low on trait Agreeableness. These results suggest that higher levels of serotonergic activity enhance greater control and consistency in social behavior among irritable–disagreeable individuals.     

Increased intraindividual variability is a marker of ADHD but also of dyslexia: a study on handwriting

It has been suggested that intraindividual variability (IIV) in neuropsychological tasks may be a specific characteristic of Attention-Deficit Hyperactivity Disorder (ADHD), but previous research has not thoroughly examined whether IIV also concerns academic performance or other types of developmental disabilities. The present study investigates the role of IIV in 15 children with ADHD without reading difficulties, 15 children with dyslexia without associated symptoms of ADHD, and 15 typically developing children (TDC) in a simple response time (SRT) task and in a skill more directly related with school learning—handwriting. Results show that children with ADHD and those with dyslexia have a greater IIV than the TDC in both tasks. However, the pattern of the relationship between IIV in SRT and handwriting was different in children with ADHD and dyslexia: the IIV in the handwriting task was found to depend on IIV in the SRT task only in children with dyslexia. These findings support the crucial role of IIV not only in ADHD but also in other developmental disabilities, but suggest that in children with ADHD it may present specific aspects related with motor control.