Effects of callosal lesions in a model of letter perception

During cognitive tasks, the cerebral hemispheres cooperate, compete, and in general, interact via the corpus callosum. Although behavioral studies in normal and split-brain subjects have revealed a great deal about the transcallosal exchange of information, a fundamental question remains unanswered and controversial: Are transcallosal interhemispheric influences primarily excitatory or inhibitory? In this context, we examined the effects of simulating sectioning of the corpus callosum in a computational model of visual letter recognition. Differences were found, following simulated callosal sectioning, in the performance of each individual hemisphere, in the mean activation levels of hemispheres, and in the specific patterns of activity, depending on the nature of the callosal influences. Together with other recent computational modeling results, the findings are most consistent with the hypothesis that transcallosal influences are predominantly excitatory, and they suggest measures that could be examined in future experimental studies to help resolve this issue.     

The Palm IAT: A portable version of the implicit association task

The Implicit Association Test (IAT) uses reaction times to measure implicit linkages among concepts or between concepts and attributes. The Palm IAT is a simplified version of the IAT that runs on Palm Pilot or Handspring Visor personal digital assistant devices. The Palm IAT is portable, provides precise measurement, and allows for efficient data collection inside or outside the laboratory. Three studies were conducted to assess its practical usefulness. Study 1 (N = 12) replicated a previous demonstration of more favorable implicit associations for flowers than for insects. Study 2 (N = 9) found individual differences in linking the self-concept to characteristics of agency and communion. Study 3 (N = 23) found individual differences in linking the self-concept to characteristics of boldness and friendliness. Reliability of the Palm IAT is similar to reliability of the original desktop computer version. Using the Palm IAT, one can study hard-to-reach populations in unusual settings.     

Shared leadership development and team performance: A new look at the dynamics of shared leadership

The present study offers new theoretical insights into the dynamics of shared leadership. Integrating arguments from shared leadership and team development theory, we examine how shared leadership changes over the course of a project team's life cycle and how this pattern of change relates to team performance. Guided by shared leadership theory and project team literature, we also explore team‐level factors, which may alter the pattern of shared leadership development. In particular, we propose that in project teams shared leadership develops in a nonuniform way, approximating an inverted U‐shaped pattern, increasing early in the team's life cycle, peaking around the midpoint, and then decreasing in the later phase. In turn, this development pattern relates positively to team performance. We also extend theory by explaining how specific team characteristics influence the pattern of shared leadership development. Using a three‐study approach, we empirically examine the hypothesized relationships and conclude with a general discussion of the theoretical and practical implications of our findings.     

<Emphasis Type="Italic">StimulStat</Emphasis>: A lexical database for Russian

In this article, we present StimulStat – a lexical database for the Russian language in the form of a web application. The database contains more than 52,000 of the most frequent Russian lemmas and more than 1.7 million word forms derived from them. These lemmas and forms are characterized according to more than 70 properties that were demonstrated to be relevant for psycholinguistic research, including frequency, length, phonological and grammatical properties, orthographic and phonological neighborhood frequency and size, grammatical ambiguity, homonymy and polysemy. Some properties were retrieved from various dictionaries and are presented collectively in a searchable form for the first time, the others were computed specifically for the database. The database can be accessed freely at http://stimul.cognitivestudies.ru.     

Planning and self-efficacy interventions encouraging replacing energy-dense foods intake with fruit and vegetable: A longitudinal experimental study

Objective: This longitudinal experimental study compared effects of self-efficacy, planning and education-based conditions, encouraging adolescents to eat fruit and vegetable in place of energy-dense foods.

Design: Data were collected among 506 adolescents (13–18 years old) who were randomly assigned to control (n = 181), planning (n = 153) or self-efficacy (n = 172) conditions. Measurements were taken at baseline (T1), at a 2-month follow-up (T2), and at a 14-month follow-up (T3). Interventions/control group procedures were delivered at T1 and T2.

Outcome measures: Self-reports of fruit and vegetable intake (FVI) and energy-dense foods intake were collected at three times. Cognitive mediators (self-efficacy and planning) were assessed at T1 and T2. Body weight and height were objectively measured at T1 and T3.

Results and conclusions: Similar significant increases of FVI were found for planning and self-efficacy interventions (T3). The planning intervention did not influence energy-dense food intake (T3), but the self-efficacy intervention tended to result in stabilising intake (compared to an increase found in the control group). There were no effects on body weight. Similar patterns were found for the total sample and for a subsample of adolescents with overweight/obesity. The effects of interventions on FVI were mediated by respective cognitions.     

Modeling development of frontal electroencephalogram (EEG) asymmetry: Sex differences and links with temperament

Asymmetric patterns of frontal brain electrical activity reflect approach and avoidance tendencies, with stability of relative right activation associated with withdrawal emotions/motivation and left hemisphere activation linked with approach and positive affect. However, considerable shifts in approach/avoidance‐related lateralization have been reported for children not targeted because of extreme temperament. In this study, dynamic effects of frontal electroencephalogram (EEG) power within and across hemispheres were examined throughout early childhood. Specifically, EEG indicators at 5, 10, 24, 36, 48, and 72 months‐of‐age (n = 410) were analyzed via a hybrid of difference score and panel design models, with baseline measures and subsequent time‐to‐time differences modeled as potentially influencing all subsequent amounts of time‐to‐time change (i.e., predictively saturated). Infant sex was considered as a moderator of dynamic developmental effects, with temperament attributes measured at 5 months examined as predictors of EEG hemisphere development. Overall, change in left and right frontal EEG power predicted declining subsequent change in the same hemisphere, with effects on the opposing neurobehavioral system enhancing later growth. Infant sex moderated the pattern of within and across‐hemisphere effects, wherein for girls more prominent left hemisphere influences on the right hemisphere EEG changes were noted and right hemisphere effects were more salient for boys. Largely similar patterns of temperament prediction were observed for the left and the right EEG power changes, with limited sex differences in links between temperament and growth parameters. Results were interpreted in the context of comparable analyses using parietal power values, which provided evidence for unique frontal effects.     

Fear generalisation in individuals with high neuroticism: increasing predictability is not necessarily better

Fear generalisation, a process by which conditioned fear spreads to similar but innocuous stimuli, is key in understanding why some individuals feel unsafe in objectively non-threatening situations. Both trait neuroticism and lack of predictability about the likelihood of feared consequences are associated with negative affect in the face of ambiguity and may increase the degree to which fear generalises. Undergraduates (N?=?129) with varying degrees of neuroticism were randomised to either high- or low-instructional predictability conditions prior to fear acquisition. A fear generalisation test measured risk ratings and attentional bias on a modified dot-probe paradigm. Among individuals with higher neuroticism, providing instructional predictability did not reduce fear; these individuals reported higher risk and increased attentional bias toward ambiguous stimuli. Overall, for individuals with higher neuroticism, predictability information hurt rather than helped interpretation of ambiguous stimuli, challenging a common conceptualisation of predictability as a factor that reduces fear.     

Age differences in cognitive performance: A study of cultural differences in Historical Context

Ethnicity and cultural experience can affect neuropsychological performance, but they are rarely assessed in historical context. Attention measures are considered strongly biologically determined and therefore potentially culture‐fair. In this study, we assessed the cross‐cultural equivalence of Spanish and English versions of the Trail Making Test (TMT; Reitan, 1958, Perceptual and Motor Skills, 8, 271–276) and the Brief Test of Attention (BTA; Schretlen et al., 1996, The Clinical Neuropsychologist, 10, 80–89) in two large samples of Americans (N = 203) and Spaniards (N = 213), divided into younger and older subgroups. The older Spaniards lived under Franco's political regime (1936–1975), whereas the Americans never experienced such repression. Overall, TMT performance was culture‐sensitive, whereas BTA performance was not. However, when both groups were stratified by age, cultural differences in TMT performance were restricted to older participants, suggesting that historical experience across generations might have contributed to the observed differences in cognitive performance. Even such basic cognitive processes as attention, working memory, and resource sharing might be shaped to some degree by historical experiences that contribute to cultural differences.     

Autism: Hard to Switch from Details to the Whole

It has long been proposed that individuals with autism exhibit a superior processing of details at the expense of an impaired global processing. This theory has received some empirical support, but results are mixed. In this research we have studied local and global processing in ASD and Typically Developing children, with an adaptation of the Navon task, designed to measure congruency effects between local and global stimuli and switching cost between local and global tasks. ASD children showed preserved global processing; however, compared to Typically Developing children, they exhibited more facilitation from congruent local stimuli when they performed the global task. In addition, children with ASD had more switching cost than Typically Developing children only when they switched from the local to the global task, reflecting a specific difficulty to disengage from local stimuli. Together, results suggest that ASD is characterized by a tendency to process local details, they benefit from the processing of local stimuli at the expense of increasing cost to disengage from local stimuli when global processing is needed. Thus, this work demonstrates experimentally the advantages and disadvantages of the increased local processing in children with ASD.