The neural bases of the effects of item-nonspecific proactive interference in working memory

We reanalyzed the behavioral and fMRI data from seven previously published studies of working memory in order to assess the behavioral and neural effects of item-nonspecific proactive interference (PI; attributable to the accrual of antecedent information independent of the repetition of particular items). We hypothesized that item-nonspecific PI, implicated in age-related declines in working memory performance, is mediated by the same mechanism(s) that mediate item-specific PI (occurring when an invalid memory probe matches a memorandum from the previous trial). Reaction time increased across trials as a function of position within the block, a trend that reversed across the duration of each multiblock experiment. The fMRI analyses revealed sensitivity to item-nonspecific PI during the probe epoch in the left anterior inferior frontal gyrus and the left dorsolateral prefrontal cortex (PFC). They also revealed a negative trend, across trials, in the transient probe-evoked component of the global signal. A common PFC-based mechanism may mediate many forms of PI.     

Recency effects as a window to generalization: separating decisional and perceptual sequential effects in category learning

Accounts of learning and generalization typically focus on factors related to lasting changes in representation (i.e., long-term memory). The authors present evidence that shorter term effects also play a critical role in determining performance and that these recency effects can be subdivided into perceptual and decisional components. Experimental results based on a probabilistic category structure show that the previous stimulus exerts a contrastive effect on the current percept (perceptual recency) and that responses are biased toward or away from the previous feedback, depending on the similarity between successive stimuli (decisional recency). A method for assessing these recency effects is presented that clarifies open questions regarding stimulus generalization and perceptual contrast effects in categorization and in other domains.     

Taxonomic Examination of ADHD and Conduct Problem Comorbidity in Elementary School Children Using Cluster Analyses

Cluster analysis was used to investigate the classification of comorbid Attention Deficit Hyperactivity Disorder (ADHD) +Conduct Problems (CP). Teachers rated 1394 elementary school children on symptoms of inattention, hyperactivity/impulsivity, opposition, and conduct problems using the ADS-IV behavior-rating scale. Results suggested that a seven-cluster solution, including two distinct comorbid clusters, was the most appropriate method of classifying children according to behavioral symptoms. A one-way MANOVA showed that overall cluster profiles differed significantly from each other, whereas one-way ANOVAs indicated that clusters differed on age and symptom scores. Chi-square analyses indicated that clusters differed on gender. Post hoc analyses and effect sizes calculations revealed that the comorbid clusters differed from each other and from their single-disorder counterparts on some variables, but not on all. These results provide support for an additive conceptualisation of ADHD +CP.     

Structural contingency theory and individual differences: examination of external and internal person-team fit

This article develops and tests a structurally based, integrated theory of person-team fit. The theory developed is an extension of structural contingency theory and considers issues of external fit simultaneously with its examination of internal fit at the team level. Results from 80 teams working on an interdependent team task indicate that divisional structures demand high levels of cognitive ability on the part of teammembers. However, the advantages of high cognitive ability in divisional structures are neutralized when there is poor external fit between the structure and the environment. Instead, emotional stability becomes a critical factor among teammembers when a divisional structure is out of alignment with its environment. Individual differences seem to play little or no role in functional structures, regardless of the degree of external fit.