Some tracking problems for aerospace models with input constraints

We study tracking controller design problems for key models of planar vertical takeoff and landing (PVTOL) aircraft and unmanned air vehicles (UAVs). The novelty of our PVTOL work is the global boundedness of our controllers in the decoupled coordinates, the positive uniform lower bound on the thrust controller, the applicability of our work to cases where the velocity measurements may not be available, the uniform global asymptotic stability and uniform local exponential stability of our closed loop tracking dynamics, the generality of our class of trackable reference trajectories, and the input-to-state stability of the controller performance under actuator errors of arbitrarily large amplitude. The significance of our UAV results is the generality of the trackable trajectories, the input-to-state stability properties of the tracking dynamics with respect to additive uncertainty on the controllers, and our ability to satisfy command amplitude and command rate constraints as well as state dependent command constraints and a state constraint on the velocity. Our work is based on a Matrosov approach for converting a nonstrict Lyapunov function for the UAV tracking dynamics into a strict one, in conjunction with asymptotic strict Lyapunov function methods and bounded backstepping

Learned irrelevance, perseveration, and cognitive aging : a cross-sectional study of cognitively unimpaired older adults

The effect of natural aging on physiologic mechanisms that regulate attentional set-shifting represents an area of high interest in the study of cognitive function. In visual discrimination learning, reward contingency changes in categorization tasks impact individual performance, which is constrained by attention-shifting costs. Perseveration (PE) and learned irrelevance (LI) are viewed as two different mechanisms that shape responses to stimuli, which are predicated on the shift in stimulus form. To date, only studies examining patients with Parkinson’s disease have provided some insight into the relationship between individual age and performance in PE and LI tasks. We enrolled 60 healthy individuals (mean [SD] age, 63.0 [12.6]) without a history of dementia, a cerebrovascular incident, or a neurodegenerative disease. No association was observed between crystallized intelligence or verbal fluency scores and reaction time in both PE (r = 0.074, p = 0.603; r = −0.124, p = 0.346) and LI (r = −0.076, p = 0.562; r = −0.081, p = 0.536) task conditions, respectively. In contrast, a statistically significant linear relationship was observed between age and reaction time (RT) for PE (r = 0.259, p = 0.046) but not for LI (r = 0.226, p = 0.083). No significant linear relationship was observed for changing RTs in PE and LI (r = 0.209, p = 0.110). The present study is the first report that provides a descriptive overview of age-related differences in PE and LI in a sample of cognitively unimpaired middle- to older-aged adults

Temperamental variation in learned irrelevance in humans

BACKGROUND Learned irrelevance (LIRR) represents one of the mechanisms of attentional set-shifting and refers to the inability to attend to, or to learn about, any aspect of a stimulus previously experienced as irrelevant. Although it has been extensively studied in the context of clinical populations, not much is known about LIRR effects in relation to normal variation in individual differences. The present study was designed to assess how temperamental factors may modulate LIRR. PARTICIPANTS AND PROCEDURES Sixty-eight healthy volunteers performed a visual discrimination learning task modelled after Wisconsin Card Sorting Test. To test the susceptibility to learned irrelevance, participants were expected to shift their attention either to a dimension that prior to the extra-dimensional shift was completely irrelevant, or to a dimension that was previously partly correlated with reinforcement. Temperamental traits were assessed using the Formal Characteristics of Behaviour-Temperament Inventory (Zawadzki & Strelau, 1997). Intelligence level was stratified according to Raven\u27s Advanced Progressive Matrices (Raven, Raven, & Court, 2003). RESULTS Low level of Briskness and high level of Perseverance were related to enhanced susceptibility to LIRR. High levels of Activity and Emotional Reactivity were related to the poorer performance on the extra-dimensional set-shifting. No effects of other temperament characteristics or intelligence on LIRR were observed. CONCLUSIONS The results confirm a strong variation in LIRR related to individual differences in temperament, which appears to be unrelated to DA function. Our results highlight the importance of considering individual differences in studies on cognitive control

Limitations of working memory capacity : the cognitive and social consequences

This paper aimed to explore, from the perspective of cognitive psychology, the natural limitations of human cognition that determine our capabilities to deal with information overflow. These limitations are related mainly to the working memory system. This system is conceived to be composed of the storage components, which are responsible for active maintenance, and executive control that supervises the storage units. People differ in their working memory capacities, and because virtually every complex cognitive activity requires the temporal availability of a certain amount of cognitive representations, these differences are predictive of many outcomes. In the area of "cold" cognition, these outcomes include intelligence and verbal reasoning, multitasking, language comprehension and verbal fluency, whereas in the area of ‘hot’ cognition, they include mentalising, stereotyping and self-control. Natural limitations in working memory capacity may be overcome (to some extent) through the training of working memory skills or the application of processing strategies (e.g. task simplification, using external environment as in situated or distributed cognition, changing a code of mental representation)

The two-factor structure of cognitive flexibility : tempo of switching and overcoming of prepotent responses

Prezentowane badanie miało na celu odkrycie struktury procesów latentnych leżących u podstaw wykonania kilku zadań, które hipotetycznie mierzą spontaniczną i adaptacyjną giętkość poznawczą, dostarczając dowodów na ich trafność zbieżną. Grupa zdrowych ochotników (N = 121) ukończyła dwa zestawy zadań do oceny spontanicznej i adaptacyjnej giętkości poznawczej. Spontaniczna giętkość poznawcza obejmowała test myślenia dywergencyjnego (do oceny płynności i giętkości myślenia) oraz werbalny test płynności. Miary giętkości adaptacyjnej obejmowały test przełączania się między zadaniami jako miarę kosztów przełączania oraz test przerzucania uwagi jako miarę wyuczonej nieistotności i perseweracji. Natomiast test znajomości słownictwa dostarczył zastępczej miary inteligencji skrystalizowanej . Analiza klastrów hierarchicznych analiza metodą Warda wykazała istnienie dwóch odrębnych podgrup zmiennych. Pierwsza grupa obejmowała płynność i giętkość myślenia, inteligencję skrystalizowaną, płynność werbalną oraz koszty przełączania się. Druga grupa obejmowała zmienne z zadania wymagającego przełączania uwagi, czyli wyuczoną nieadekwatność i persewerację. Uważamy, że te wyniki są znaczące i wskazują na udział dwóch oddzielnych czynników kształtujących giętkość poznawczą: (a) tempo przełączania i (b) przezwyciężanie dominujących reakcji. W podsumowaniu omówiono implikacje tych wyników dla oceny giętkości poznawczej.The current study aimed to uncover the structure of common latent processes underlying the execution of several tasks that hypothetically measure spontaneous and adaptive cognitive flexibility, providing evidence for their convergent validity. A group of healthy volunteers (N = 121) completed two sets of tasks to assess spontaneous and adaptive cognitive flexibility. Spontaneous flexibility measures included a divergent thinking test (to assess fluency and flexibility of thinking) and a verbal fluency test. Adaptive flexibility measures involved a set-switching test as a measure of switch costs and an attentional set-shifting test as a measure of learned irrelevance and perseveration). A vocabulary knowledge test provided a proxy measure of crystallized intelligence. Hierarchical cluster analysis using Ward's method revealed the existence of two separate subgroups of variables. The first group comprised fluency and flexibility of thinking, crystallized intelligence, verbal fluency, and switch costs. The second group included attentional shift variables, that is, learned irrelevance and perseveration. We consider these results meaningful and indicative of two separate factors contributing to cognitive flexibility: (a) speed of switching and (b) overcoming of prepotent responses. We discuss the implications of our results for the assessment of cognitive flexibility

The role of strigolactones in nutrient-stress responses in plants

Strigolactones (SLs) are a new group of plant hormones, which have been intensively investigated during the last few years. The wide spectrum of SLs actions, including the regulation of shoot/root architecture, and the stimulation of the interactions between roots and fungi or bacteria, as well as the stimulation of germination of parasitic plants, indicates that this group of hormones may play an important role in the mechanisms that control soil exploration, and the root-mediated uptake of nutrients. Current studies have shown that SLs might be factors that have an influence on the plant response to a deficiency of macronutrients. Experimental data from the last four years have confirmed that the biosynthesis and exudation of SLs are increased under phosphorus and nitrogen deficiency. All these data suggest that SLs may regulate the complex response to nutrient stress, which include not only the modification of the plant developmental process, but also the cooperation with other organisms in order to minimize the effects of threats. In this paper the results of studies that indicate that SLs play an important role in the response to nutrient stress are reviewed and the consequences of the higher biosynthesis and exudation of SLs in response to phosphorus and nitrogen deficiency are discussed

Understanding factors behind the effectiveness of personal identification : revolution - a new technique of creative problem solving

Although it is widely believed that inducing a change in mental perspective through personal identification with an object facilitates problem solving, empirical evidence that supports this thesis is limited. The present study aimed at recognition of factors determining the effectiveness of personal identification by verifying the efficiency of a new technique of creative problem solving called Revolution. Forty-six subjects participating in the naturalistic study were randomly assigned to five experimental groups testing several versions of Revolution. The following factors were manipulated: personal identification (presence versus lack of identification), problem type (abstract versus specific) and time lag between the preparation stage (preparing the project) and the execution stage. Solutions generated by different groups were evaluated by a team of eight competent judges using the Creative Product Semantic Scale. There was no difference in the overall quality of the solutions when problem type variable was under consideration. Surprisingly, identification appeared to have a negative impact on product creativity (as evaluated by the judges). Detailed analyses revealed that the negative influence of personal identification was limited to specific task conditions, implying that it can be neutralized by separating the preparation from execution stage. The implications of the present results are discussed

The (in)significance of executive functions for the trait of Self-Control : a psychometric study

Self-control (SC) is an individual trait defined as the ability to pursue long-distance goals in spite of the obstacles generated by current desires, innate or learned automatisms, and physiological needs of an organism. This trait is relatively stable across the life span and it predicts such important features as level of income, quality of social relationships, and proneness to addictions. It is widely believed that the cognitive substrate of SC involves the executive functions (EFs), such as inhibitory control, shifting of attention, and working memory updating. However, the empirical evidence concerning the relationships between trait SC and EFs is not convincing. The present study aims to address two questions: (1) what is the strength of relationships between trait SC and EFs, and (2) which aspects of SC are predicted by particular EFs, if at all. In order to answer these questions, we carried out a psychometric study with 296 participants (133 men and 163 women, mean age 23.31, SD 3.64), whom we investigated with three types of tools: (1) a battery SC scales and inventories, (2) a battery of EFs tasks, and (3) two general intelligence tests. Structural equation modeling approach was used to analyze the data. We found that the latent variables representing SC and the latent variable representing EFs did not show any relationship. The standardized path coefficient between EFs and general intelligence turned out rather strong. We conclude that the trait of SC, measured with questionnaires, does not depend on the strength of cognitive control, measured with EFs tasks

NAS-50 and NAS-40 : new scales for the assessment of self-control

In this paper, we present a new questionnaire for the assessment of self-control as an individual trait. We describe the process of construction of this assessment tool. We also report the results of relevant validation studies. The questionnaire has two independent versions, one based on self-reports (NAS-50) and another one based on other-reports (NAS-40). The first version consists of five subscales (10 items each), called Initiative and Persistence (IP), Proactive Control (PC), Switching and Flexibility (SF), Inhibition and Adjournment (IA), and Goal Maintenance (GM). Seven samples of participants (N = 934 altogether) took part in the validation study. The second version has not been split into subscales. Both versions obtained satisfactory indices of internal consistency, assessed with Cronbach’s alpha (for NAS- 50 total score a = .861, for the subscales a between .726 and .867; for NAS-40 a = .844). The NAS-50 and NAS-40 scores were highly correlated with other measures of self-control, including Tangney, Baumeister, and Boone’s (2004) self-control scale. They also proved to be entirely independent of general intelligence. In conclusion, both versions can be regarded reliable and valid enough, and therefore suitable for the assessment of trait self-control for research purposes