Thinking about muscles: the neuromuscular effects of attentional focus on accuracy and fatigue

Although the effects of attention on movement execution are well documented behaviorally, much less research has been done on the neurophysiological changes that underlie attentional focus effects. This study presents two experiments exploring effects of attention during an isometric plantar-flexion task using surface electromyography (sEMG). Participants' attention was directed either externally (towards the force plate they were pushing against) or internally (towards their own leg, specifically the agonist muscle). Experiment 1 tested the effects of attention on accuracy and efficiency of force produced at three target forces (30, 60, and 100% of the maximum voluntary contraction; MVC). An internal focus of attention reduced the accuracy of force being produced and increased cocontraction of the antagonist muscle. Error on a given trial was positively correlated with the magnitude of cocontraction on that trial. Experiment 2 tested the effects of attention on muscular fatigue at 30, 60 and 100%MVC. An internal focus of attention led to less efficient intermuscular coordination, especially early in the contraction. These results suggest that an internal focus of attention disrupts efficient motor control in force production resulting in increased cocontraction, which potentially explains other neuromechanical findings (e.g. reduced functional variability with an internal focus).     

Dopamine, working memory, and training induced plasticity: implications for developmental research

Cognitive deficits and particularly deficits in working memory (WM) capacity are common features in neuropsychiatric disorders. Understanding the underlying mechanisms through which WM capacity can be improved is therefore of great importance. Several lines of research indicate that dopamine plays an important role not only in WM function but also for improving WM capacity. For example, pharmacological interventions acting on the dopaminergic system, such as methylphenidate, improve WM performance. In addition, behavioral interventions for improving WM performance in the form of intensive computerized training have recently been associated with changes in dopamine receptor density. These two different means of improving WM performance--pharmacological and behavioral--are thus associated with similar biological mechanisms in the brain involving dopaminergic systems. This article reviews some of the evidence for the role of dopamine in WM functioning, in particular concerning the link to WM development and cognitive plasticity. Novel data are presented showing that variation in the dopamine transporter gene (DAT1) influences improvements in WM and fluid intelligence in preschool-age children following cognitive training. Our results emphasize the importance of the role of dopamine in determining cognitive plasticity.     

Kullback–Leibler Information and Its Applications in Multi-Dimensional Adaptive Testing

This paper first discusses the relationship between Kullback–Leibler information (KL) and Fisher information in the context of multi-dimensional item response theory and is further interpreted for the two-dimensional case, from a geometric perspective. This explication should allow for a better understanding of the various item selection methods in multi-dimensional adaptive tests (MAT) which are based on these two information measures. The KL information index (KI) method is then discussed and two theorems are derived to quantify the relationship between KI and item parameters. Due to the fact that most of the existing item selection algorithms for MAT bear severe computational complexity, which substantially lowers the applicability of MAT, two versions of simplified KL index (SKI), built from the analytical results, are proposed to mimic the behavior of KI, while reducing the overall computational intensity.     

Frequency drives lexical access in reading but not in speaking: the frequency-lag hypothesis

To contrast mechanisms of lexical access in production versus comprehension we compared the effects of word frequency (high, low), context (none, low constraint, high constraint), and level of English proficiency (monolingual, Spanish-English bilingual, Dutch-English bilingual) on picture naming, lexical decision, and eye fixation times. Semantic constraint effects were larger in production than in reading. Frequency effects were larger in production than in reading without constraining context but larger in reading than in production with constraining context. Bilingual disadvantages were modulated by frequency in production but not in eye fixation times, were not smaller in low-constraint contexts, and were reduced by high-constraint contexts only in production and only at the lowest level of English proficiency. These results challenge existing accounts of bilingual disadvantages and reveal fundamentally different processes during lexical access across modalities, entailing a primarily semantically driven search in production but a frequency-driven search in comprehension. The apparently more interactive process in production than comprehension could simply reflect a greater number of frequency-sensitive processing stages in production.     

Reliability and validity of a bilingual measure of religiosity in English and Vietnamese: preliminary results from a pilot study

This study reports preliminary psychometric findings for a seven-item religiosity scale in a community-based sample of Vietnamese Americans ages 18 to 83 years (N = 119; 58% women, 42% men). A bilingual survey was distributed to Vietnamese who were evacuated during Hurricane Katrina and had returned after the disaster. Internal consistency, factorial structure validity, and criterion validity were evaluated on the scale items. The bilingual scale had good internal consistency. While exploratory and confirmatory factor analysis results provided support for a two-factor structure which captured Religious Involvement and Religious Coping, a one-factor model had slightly better fit. Individuals who scored high on the religiosity scale reported a significantly lower score on their stressful experiences during the hurricane, providing evidence of criterion validity.     

Evaluating a brief measure of social self-efficacy among U.S. adolescents

Preliminary data were collected to evaluate the performance of a social self-efficacy measure among 4,061 public high school adolescents. Principal-axis factor analysis was followed by a 4-way between-groups analysis of variance (ANOVA) to test for differences in the Total score means on selected demographic estimates and their interactions. Relations between the Total score and selected risk behaviors were examined through a series of one-way ANOVAs and the Tukey HSD test. Factor analysis results suggested a one-factor model best explained the factor structure of the scale items (factor loading range = .64 - .77, eigenvalue = 4.05, h(2) = .51). Females reported a significantly higher mean Total social self-efficacy rating than males, while White students reported a significantly higher mean Total social self-efficacy rating than Black and Asian students. Statistically significant lower mean Total social self-efficacy ratings were also noted for those who reported physical fighting, avoiding school, and being bullied.     

The evolution of decision-making under risk: Framing effects in monkey risk preferences

When making choices between risky options, human decision-makers exhibit a number of framing effects. One of the most prominent framing effects is the tendency for decision makers to evaluate gambles relative to a reference point, and to act risk-seeking when prospects are framed as losses but risk-averse when identical prospects are framed as gains. This tendency for risk-preferences to reverse between loss and gain frames has been termed the reflection effect, and is one of the primary predictions of Prospect Theory. Here, we explore whether non-human primates exhibit a similar reflection effect. Using a token-trading task, we show that capuchin monkeys (Cebus apella) exhibit an analogous reversal of risk preferences depending on whether outcomes are presented as gains or losses, suggesting that similar framing effects also influence choice in non-human primates. This finding suggests that the mechanisms that drive framing effects in humans may be evolutionarily ancient, extending broadly across the primate order.     

Developmental Risk and Young Children’s Regulatory Strategies: Predicting Behavior Problems at Age Five

Children with early developmental delays are at heightened risk for behavior problems and comorbid psychopathology. This study examined the trajectories of regulatory capabilities and their potentially mediating role in the development of behavior problems for children with and without early developmental delays. A sample of 231 children comprised of 137 typically developing children and 94 children with developmental delays were examined during mildly frustrating laboratory tasks across the preschool period (ages 3–5). Results indicated that children with delays had greater use of maladaptive strategies (distraction, distress venting) and lower use of adaptive strategies (constructive coping) than typically developing children. For both groups, strategies had similar rates of growth across time; maladaptive strategies decreased and adaptive strategies increased. The intercept of strategy use, but not the slope, was found to mediate the relation between developmental risk and externalizing behaviors. Findings support that dysregulation, rather than the developmental risk, may be responsible for the high levels of comorbid psychopathology.     

Eye movements and display change detection during reading

In the boundary change paradigm (Rayner, 1975), when a reader's eyes cross an invisible boundary location, a preview word is replaced by a target word. Readers are generally unaware of such changes due to saccadic suppression. However, some readers detect changes on a few trials and a small percentage of them detect many changes. Two experiments are reported in which we combined eye movement data with signal detection analyses to investigate display change detection. On each trial, readers had to indicate if they saw a display change in addition to reading for meaning. On half the trials the display change occurred during the saccade (immediate condition); on the other half, it was slowed by 15-25 ms (delay condition) to increase the likelihood that a change would be detected. Sentences were presented in an alternating case fashion allowing us to investigate the influence of both letter identity and case. In the immediate condition, change detection was higher when letters changed than when case changed corroborating findings that word processing utilizes abstract (case independent) letter identities. However, in the delay condition (where d' was much higher than the immediate condition), detection was equal for letter and case changes. The results of both experiments indicate that sensitivity to display changes was related to how close the eyes were to the invalid preview on the fixation prior to the display change, as well as the timing of the completion of this change relative to the start of the post-change fixation.