Statistical methods for absorbing Markov-chain models for learning: Estimation and identification

General algorithms for computing the likelihood of any sequence generated by an absorbing Markov-chain are described. These algorithms enable an investigator to compute maximum likelihood estimates of parameters using unconstrained optimization techniques. The problem of parameter identifiability is reformulated into questions concerning the behavior of the likelihood function in the neighborhood of an extremum. An alternative characterization of the concept of identifiability is proposed. A procedure is developed for deciding whether or not this definition is satisfied.This research was undertaken within the Institute for the Study of Intellectual Behavior, University of Colorado, and is Publication No. 42 of the Institute. The work was supported by NSF Grant GB-34077X. The logic underlying Algorithm I was suggested by Clint Schumacher.     

Age-Related Changes in Executive Function: A Normative Study with the Dutch Version of the Behavior Rating Inventory of Executive Function (BRIEF)

This study examined age-related change in executive function by using a Dutch translation of the Behavior Rating Inventory of Executive Function (BRIEF; Gioia et al., 2000 Gioia, G. A., Isquith, P. K., Guy, S. C. and Kenworthy, L. 2000. Behavior Rating Inventory of Executive Function BRIEF): Professional manual, Lutz, FL: Psychological Assessment Resources.  [Google Scholar]) that was applied to a normative sample (age range 5–18 years). In addition, we examined the reliability and factorial structures of the Dutch BRIEF. Results with respect to age revealed a decrease in reported executive function problems with increasing age. On the Behavior Regulation Index (BRI), 5- to 8-year-olds showed significantly more executive function problems than 9- to 11-year-olds, as did the 12- to 14-year-olds compared to 15- to 18-year-olds (except on the Shift subscale). On the Metacognition Index, we found that 9- to 11-year-olds differed significantly from 5- to 8-year-olds on the Working Memory subscale. In addition, the current study showed that the internal consistency of the Dutch BRIEF is very high, and that this version of the BRIEF has a high test-retest stability. Item factor analysis confirmed the expected eight common factor model, and factor analysis of the eight test scores confirmed the two-factor model, as proposed by Gioia et al., in the Dutch data.     

Predictors of Resilience Among Inner City Youths

Prior studies have suggested that living in high-risk neighborhoods is associated with youths’ maladjustment. Youths who maintained favorable outcomes, despite being exposed to such neighborhood risks, were considered resilient. Using structural equation modeling techniques, longitudinal data of 877 youths from the Denver Youth Survey were examined to identify predictors of resilience, longitudinal interrelations among predictors, and bi-directional relationships between resilience and life context factors. Resilience was longitudinally predicted by bonding to family and teachers, involvement in extracurricular activities, lower levels of parental discord, fewer adverse life events, and being less involved with delinquent peers. A positive feedback loop was found, in which resilience predicted further resilience. Early intervention to strengthen traditional bonding, decrease involvement with delinquent peers, and reduce the effects of adverse life events and parental discord may be essential in enhancing functioning of high-risk youths.     

Age-Related Change in Shifting Attention Between Global and Local Levels of Hierarchical Stimuli

The focus of this study was the developmental pattern of the ability to shift attention between global and local levels of hierarchical stimuli. Children aged 7 years and 11 years and 21-year-old adults were administered a task (two experiments) that allowed for the examination of 1) the direction of attention to global or local stimulus levels; 2) the susceptibility to interference of the global or local stimulus levels; and 3) the flexibility in directing attention to global or local stimulus levels. The results revealed a global advantage effect that decreased with age when the task required level shifting from trial to trial. The abilities to resist interference and to flexibly shift attention also improved during childhood, but quickly leveled off during adolescence. The ability to shift attention was found to be unrelated to processes contributing to global advantage. The results suggest that the ability to flexibly shift attention to and away from local detail, to provide the most adaptive response, continues to develop during childhood into adulthood.     

Task switching and shifting between stopping and going: Developmental change in between-trial control adjustments

This study set out to investigate developmental differences in the ability to switch between choice tasks and to shift between Go/NoGo and choice tasks. Three age groups (7-year-olds, 11-year-olds, and young adults) were asked to consider the shape or color of a bivalued target stimulus. The participants performed a switch task in which a cue signaled the task to be performed (i.e., respond to shape vs. respond to color) and a shift task in which a cue instructed them to make a choice reaction to the shape of the stimulus or to respond (Go) versus inhibit (NoGo) to the color of the stimulus. The ability to switch was examined by considering choice-choice switches versus choice-choice repeats. The ability to shift was examined by considering NoGo-to-choice shifts versus choice-choice repeats and NoGo-to-Go shifts versus Go-Go repeats. The results showed that responding on Go trials was delayed following response inhibition on a NoGo trial. This delay did not discriminate between age groups. Responding on choice trials was considerably slowed when following response inhibition on NoGo trials. This slowing decreased with advancing age. Finally, responses on switch trials were slower compared with repeat trials, and this slowing was disproportionately large in young children compared with the other two age groups. This pattern of findings was interpreted in terms of a generic mechanism involving between-trial control adjustments in the setting of response thresholds that are likely to be mediated by a complex neural network implicating the dorsolateral prefrontal cortex and the presupplementary motor cortex.     

Rapid cerebral hemodynamic modulation during set shifting: Evidence of time-locked associations with cognitive control in females

Set shifting provokes specific alterations of cerebral hemodynamics in basal cerebral arteries. However, no gender differences have been reported. In the following functional transcranial Doppler study, we introduced cerebral hemodynamic modulation to the aspects of set shifting during Wisconsin Card Sorting Test (WCST). Twenty-one subjects underwent the WCST during insonation of the middle cerebral arteries. We examined gender effects on task performance and cerebral hemodynamic modulation. Further, we investigated the linkage between performance and cerebral hemodynamic modulation. In females, maximum positive modulation was restricted to the behaviorally relevant time point of set shifting, and there were time-locked associations between mental slowing during set shifting and rapid cerebral hemodynamic modulation exclusively in females. This study provides evidence of gender-related cerebral hemodynamic modulation during set shifting, and we detected time-locked brain–behavior relationship during cognitive control in females.     

Testing the Role of Aspirations,Future Expectations,and Strain on the Development of Problem Behaviors across Young and Middle Adulthood

Using prospective data collected across 14 years by the National Youth Survey Family Study (N = 1,436), we assessed change in aspirations, future expectations, and strain, as well as contemporaneous and longitudinal effects of these predictors on drug use, offending, and the perpetration of intimate partner violence. Growth curve models showed that, although time significantly predicted change in these variables, trajectories remained relatively stable. Contemporaneous random-intercept regression models revealed that all three measures were associated with all three problem behaviors. The effects were predictive longitudinally but some associations and gender differences were attenuated when controlling for prior involvement in outcomes.     

Variation in reversal learning by three generalist mesocarnivores

Animal Cognition - Urbanization imposes novel challenges for wildlife, but also provides new opportunities for exploitation. Generalist species are commonly found in urban habitats, but the...